Drug therapy for OCD | AQA A-Level Psychology Revision
- Revision Notes
- Aug 3
- 26 min read
Updated: 7 days ago
For 7182 specification, first teach in September 2025
AQA A-Level Psychology | Free Revision Notes
Estimated study time: 45 minutes
These Drug therapy for OCD A-Level Psychology revision notes explain how medication may reduce obsessive thoughts, anxiety and compulsive behaviour. The main biological treatment is a selective serotonin reuptake inhibitor, which increases serotonin activity at the synapse. You will also examine alternative drugs, the connection between medication and biological explanations, and important questions about effectiveness, side effects, treatment delay, client suitability and the treatment fallacy. The AQA specification requires drug therapy as the biological approach to treating OCD.
Learning Objectives 🎯
By the end of this revision page, you should be able to:
Explain how drug therapy is used to treat OCD.
Describe how selective serotonin reuptake inhibitors affect synaptic transmission.
Outline alternative drugs that may be used.
Link drug therapy to genetic and neural explanations of OCD.
Apply drug-treatment principles to unfamiliar scenarios.
Evaluate the effectiveness of drug therapy.
Evaluate whether drug therapy is appropriate for different clients.
Revision Notes 📚
Drug therapy for OCD A-Level Psychology revision overview
Drug therapy involves using medication to alter biological processes associated with obsessive-compulsive disorder, usually shortened to OCD.
Medication aims to reduce symptoms such as:
Intrusive obsessive thoughts.
Anxiety and distress.
Compulsive behaviour.
Difficulty dismissing worries.
Repetitive checking or washing.
Interference with everyday functioning.
The main drugs used are antidepressants that affect serotonin transmission.
The most important group is:
Selective serotonin reuptake inhibitors, usually shortened to SSRIs.
Other possible medications include:
Tricyclic antidepressants.
Serotonin-noradrenaline reuptake inhibitors.
Drugs that reduce anxiety.
The biological rationale is:
If abnormal neurotransmitter functioning contributes to OCD, changing neurotransmitter activity may reduce its symptoms.
Drug therapy is a treatment, not an explanation
A treatment describes how symptoms may be reduced.
An explanation describes why OCD may develop.
For example:
Abnormal serotonin functioning is part of the neurochemical and brain-circuit account of OCD.
The SERT gene may form part of inherited vulnerability to OCD.
An SSRI is a treatment intended to alter serotonin transmission.
Do not replace a treatment answer with a description of genes or brain structures.
A strong answer may link them, but the treatment procedure must remain the focus.
The biological basis of drug therapy
The biological approach proposes that OCD is associated with atypical biological functioning.
Relevant factors include:
Reduced or abnormal serotonin transmission.
Atypical dopamine functioning.
Overactivity in neural circuits associated with worry.
Impaired filtering of minor concerns.
Genetic differences affecting neurotransmitter systems.
Drug therapy attempts to alter these biological processes.
The serotonin link
Serotonin is a neurotransmitter associated with processes including:
Mood regulation.
Anxiety.
Behavioural control.
Information processing.
Reduced or abnormal serotonin activity may make it harder to regulate:
Intrusive thoughts.
Worry.
Anxiety.
Repeated urges.
Drugs that increase serotonin activity may therefore reduce some OCD symptoms.
A cautious causal claim
It is too simple to state:
“OCD is caused by low serotonin.”
A more accurate statement is:
Abnormal serotonin functioning may contribute to vulnerability to or maintenance of OCD symptoms.
OCD is complex and may involve:
Several neurotransmitters.
Several brain structures.
Genetic vulnerability.
Environmental stress.
Learning and cognitive factors.
Synaptic transmission
To understand SSRIs, you need a basic understanding of the transmission of chemical signals between neurons.
The synapse
A synapse is the small gap between two neurons.
The neuron releasing a neurotransmitter is the:
Presynaptic neuron.
The neuron receiving the neurotransmitter is the:
Postsynaptic neuron.
Normal transmission
A simplified sequence is:
An electrical impulse reaches the end of the presynaptic neuron.
Serotonin is released into the synaptic gap.
Serotonin crosses the synapse.
It binds with receptor sites on the postsynaptic neuron.
The postsynaptic neuron is stimulated.
Serotonin is removed from the synapse.
Some serotonin is taken back into the presynaptic neuron.
This is called reuptake.
Why reuptake occurs
Reuptake removes serotonin from the synaptic gap and allows it to be:
Recycled.
Broken down.
Used in later transmission.
Once serotonin has been removed, it can no longer continue stimulating postsynaptic receptors.
Selective serotonin reuptake inhibitors
What is an SSRI?
A selective serotonin reuptake inhibitor is a drug that reduces the reabsorption of serotonin by the presynaptic neuron.
Examples include:
Fluoxetine.
Sertraline.
Paroxetine.
The word selective indicates that the drug primarily targets serotonin rather than affecting every neurotransmitter equally.
Breaking down the name
Part of the name | Meaning |
Selective | Primarily targets one neurotransmitter system |
Serotonin | The neurotransmitter affected |
Reuptake | Reabsorption into the presynaptic neuron |
Inhibitor | Something that reduces or blocks a process |
How an SSRI works
An SSRI blocks or reduces the action of serotonin transporter proteins.
This means:
Serotonin is released into the synapse.
It binds with postsynaptic receptors.
Reuptake into the presynaptic neuron is inhibited.
Serotonin remains available in the synaptic gap for longer.
It continues stimulating the postsynaptic neuron.
Serotonin transmission is increased.
Official AQA marking guidance describes SSRIs as preventing serotonin reabsorption so that serotonin continues stimulating the postsynaptic neuron.
Before an SSRI
Serotonin released → binds to receptors → quickly reabsorbed
After an SSRI
The purpose of treatment
Increasing serotonergic activity may help reduce:
Anxiety.
Distress.
Persistence of obsessive thoughts.
Urges to perform compulsions.
The amount of time spent completing rituals.
The treatment does not necessarily remove every intrusive thought.
It may make the thoughts:
Less frequent.
Less distressing.
Easier to resist.
Less likely to produce prolonged compulsions.
A step-by-step SSRI example
Imagine that Maisie experiences a recurring fear that household appliances have been left switched on.
She repeatedly checks them before leaving home.
Before treatment
Maisie experiences:
An intrusive doubt.
Intense anxiety.
Repeated checking.
Temporary relief.
A return of the doubt.
Biological explanation
Abnormal serotonin functioning may contribute to:
Poor regulation of anxiety.
Difficulty dismissing the intrusive thought.
Continued activation of worry circuits.
Drug treatment
Maisie is prescribed an SSRI.
The drug:
Inhibits serotonin reuptake.
Increases serotonin availability at synapses.
Produces continuing postsynaptic stimulation.
May improve the regulation of anxiety and obsessive thoughts.
May reduce the urge to check repeatedly.
Expected outcome
Maisie may still occasionally wonder whether an appliance is switched off.
However, the thought may:
Produce less anxiety.
Be easier to dismiss.
Be less likely to result in repeated checking.
Why SSRIs are taken regularly
SSRIs are normally taken daily rather than only when an intrusive thought occurs.
They aim to produce continuing changes in neurotransmitter functioning.
The treatment is not like taking a painkiller for immediate relief.
Delayed effects
The biological action at the synapse begins relatively quickly, but symptom reduction may take considerably longer.
Official AQA marking materials refer to:
Several weeks before noticeable improvement.
Continued daily treatment over several months.
Reviews of dosage if sufficient improvement does not occur.
Why the delay matters
If serotonin availability changes quickly but symptoms improve slowly, the effect may involve more than serotonin remaining in the synapse.
Longer-term changes may include:
Receptor adaptation.
Changes in communication between neurons.
Altered activity within neural circuits.
Gradual reduction of anxiety and compulsive routines.
This creates an evaluation point against an overly simple low-serotonin explanation.
Dosage and monitoring
A prescriber normally begins with an appropriate dose and monitors:
Symptom change.
Side effects.
Adherence.
Everyday functioning.
Changes in emotional wellbeing.
The dose may be reviewed when:
Symptoms do not improve.
Side effects are difficult to manage.
The person cannot take the medicine consistently.
Another medication may be more suitable.
Students do not need to recommend medication or dosage to an individual.
In an examination, focus on:
The drug category.
The biological mechanism.
The expected effect.
Evaluation of effectiveness and suitability.
What happens when an SSRI is ineffective?
Not every client benefits sufficiently from the first drug prescribed.
Possible next steps may include:
Continuing treatment for an appropriate period before judging it.
Reviewing the dose.
Trying a different SSRI.
Considering another antidepressant.
Considering a different form of treatment.
This variation in response suggests that OCD may not have one identical biological cause in every person.
Alternative drug treatments
Why alternatives may be used
An alternative may be considered when:
The SSRI produces insufficient improvement.
Side effects are unacceptable.
The client cannot take the medication.
A different neurotransmitter mechanism may be relevant.
Official AQA mark schemes identify tricyclic antidepressants, serotonin-noradrenaline reuptake inhibitors and anxiety-reducing drugs as alternatives.
Tricyclic antidepressants
What is a tricyclic antidepressant?
A tricyclic antidepressant is an older type of antidepressant.
Clomipramine is one example associated with the treatment of OCD.
Tricyclics may increase the availability of neurotransmitters by reducing their reuptake.
They can affect:
Serotonin.
Noradrenaline.
When might a tricyclic be used?
A tricyclic may be considered when:
An SSRI has not produced sufficient improvement.
The client can tolerate the medication.
The potential benefits outweigh the risks.
Possible disadvantage
Tricyclic antidepressants generally produce more significant side effects than SSRIs.
Possible effects may include:
Dry mouth.
Drowsiness.
Dizziness.
Changes in blood pressure.
Potential heart-related effects.
This can make them less appropriate as the first treatment offered.
Serotonin-noradrenaline reuptake inhibitors
What is an SNRI?
A serotonin-noradrenaline reuptake inhibitor, usually shortened to SNRI, reduces the reuptake of:
Serotonin.
Noradrenaline.
This increases the availability of both neurotransmitters within relevant synapses.
Comparison with an SSRI
SSRI | SNRI |
Mainly affects serotonin | Affects serotonin and noradrenaline |
Common first biological treatment | May be considered as an alternative |
Blocks serotonin reuptake | Blocks reuptake of two neurotransmitters |
Side effects vary between clients | Side effects also vary between clients |
Anxiety-reducing drugs
Some drugs may reduce general anxiety or physiological arousal.
For example, benzodiazepines may produce relaxation and reduce anxiety.
This could make obsessive thoughts less distressing.
However, these drugs may involve disadvantages such as:
Drowsiness.
Reduced alertness.
Tolerance.
Dependence when used for extended periods.
They are therefore not a simple long-term solution to every form of OCD.
Comparison of drug types
Drug type | Main biological action | Possible benefit | Possible limitation |
SSRI | Inhibits serotonin reuptake | May reduce obsessions, anxiety and compulsions | Delayed effect and possible side effects |
Tricyclic antidepressant | Reduces reuptake of serotonin and noradrenaline | Alternative when SSRIs are ineffective | Often more severe side effects |
SNRI | Inhibits serotonin and noradrenaline reuptake | Targets more than one neurotransmitter | Not effective or appropriate for everyone |
Anxiety-reducing drug | Reduces general arousal and anxiety | May reduce immediate distress | Drowsiness, tolerance or dependence may occur |
Linking drug therapy with neural explanations
Drug therapy follows logically from neural explanations of OCD.
Serotonin explanation
Neural explanation:
Abnormal serotonin transmission contributes to difficulty regulating anxiety and obsessive thoughts.
Treatment:
An SSRI inhibits serotonin reuptake and increases serotonergic activity.
Expected result:
Anxiety and obsessive-compulsive symptoms may decrease.
Dopamine explanation
Neural explanation:
Atypical dopamine functioning may contribute to repetitive behaviour and difficulty controlling actions.
Treatment implication:
Drug research may investigate medications affecting wider neurotransmitter systems.
However, standard OCD drug therapy focuses most strongly on serotonin.
Brain-circuit explanation
The worry circuit may involve abnormal activity in:
The orbitofrontal cortex.
The caudate nucleus.
The thalamus.
Increasing serotonin activity may alter communication within this circuit.
The treatment may reduce:
Persistent threat signals.
Failure to dismiss minor worries.
Repeated urges to complete compulsions.
Drug therapy does not directly repair one structure
It is inaccurate to say:
“SSRIs repair the caudate nucleus.”
SSRIs alter neurotransmitter transmission.
Any changes in circuit activity are indirect and occur through the interaction of many neurons.
Linking drug therapy with genetic explanations
Genetic explanations propose that inherited gene variants may affect neurotransmitter systems.
For example:
The SERT gene is associated with the serotonin transporter.
Variants may influence serotonin reuptake.
Altered serotonergic communication may increase vulnerability to OCD.
An SSRI also affects the serotonin transporter.
The link can be represented as:
SERT gene variant → altered serotonin transport → increased vulnerability → SSRI inhibits reuptake → serotonin availability increases
What this link shows
The connection gives drug therapy a biological rationale.
It suggests that:
Inherited differences may influence neurochemistry.
Medication may target part of the resulting biological system.
What it does not show
It does not prove that:
The SERT gene caused the disorder.
Every client possesses the same gene variant.
Every client will respond to an SSRI.
The drug reverses the original cause.
Environmental factors are irrelevant.
OCD is considered polygenic and aetiologically heterogeneous.
Different people may have different combinations of:
Genetic risk.
Neural functioning.
Life experiences.
Psychological processes.
Drug therapy and OCD characteristics
Drug therapy aims to reduce features described in obsessions, compulsions and associated emotional difficulties.
Cognitive effects
Medication may reduce:
Frequency of intrusive thoughts.
Intensity of obsessional doubt.
Selective attention to the source of worry.
Difficulty dismissing a concern.
Emotional effects
Medication may reduce:
Anxiety.
Distress.
Low mood associated with symptoms.
Guilt or emotional discomfort.
Behavioural effects
Medication may reduce:
Repeated checking.
Repeated washing.
Reassurance-seeking.
Ritualised behaviour.
Avoidance.
A person does not need to show improvement in every category for treatment to have value.
Assessing effectiveness
What does effectiveness mean?
Effectiveness refers to the extent to which a treatment produces meaningful improvement.
Drug therapy may be judged effective when it produces:
Reduced symptom severity.
Fewer compulsions.
Less time spent completing rituals.
Reduced anxiety.
Improved everyday functioning.
Benefits that continue during treatment.
Greater ability to participate in ordinary activities.
Symptom reduction
A clinician may assess:
How often obsessions occur.
How distressing they are.
How long compulsions take.
How difficult rituals are to resist.
Whether daily functioning has improved.
Functional improvement
A change in symptom score is useful, but practical improvement is also important.
For example, treatment may allow a person to:
Leave home on time.
Attend education or employment.
Use shared facilities.
Sleep more regularly.
Maintain relationships.
Complete personal care without lengthy rituals.
Complete recovery is not required
A drug may be clinically useful even if it does not eliminate every symptom.
For example:
Checking falls from several hours to several minutes.
Anxiety becomes manageable.
Intrusive thoughts remain but no longer dominate behaviour.
Evaluating the effectiveness of drug therapy
Strength: drug treatments can reduce OCD symptoms
Research and clinical use indicate that serotonin-based medication can reduce symptoms for many clients.
This supports the view that serotonin is involved in OCD.
Possible improvements include:
Less intense anxiety.
Reduced frequency of obsessions.
Fewer compulsive actions.
Better everyday functioning.
Strength: medication targets a measurable biological process
SSRIs have an identifiable mode of action.
They:
Inhibit serotonin reuptake.
Increase serotonin availability.
Continue postsynaptic stimulation.
This gives the treatment a clear and scientifically testable rationale.
Researchers can investigate:
Changes in symptoms.
Dosage.
Side effects.
Neurotransmitter activity.
Brain functioning.
Strength: medication may reduce several symptoms together
OCD involves interconnected:
Thoughts.
Emotions.
Behaviours.
Reducing anxiety may make:
Obsessions less distressing.
Compulsions easier to resist.
Avoidance less necessary.
Everyday activities more manageable.
The treatment may therefore affect several areas of functioning.
Limitation: medication does not work for everyone
Some clients experience:
Strong improvement.
Partial improvement.
No meaningful improvement.
Variation in response challenges the idea that one serotonin abnormality explains every case.
It suggests:
Different biological pathways.
Different symptom profiles.
Different causes.
The involvement of non-biological factors.
Official AQA marking guidance identifies non-response to medication as a limitation of a simple neural explanation and drug treatment.
Limitation: improvement may be incomplete
A person may experience reduced anxiety but continue:
Having intrusive thoughts.
Completing rituals.
Avoiding triggers.
Believing that the compulsion prevents danger.
Drug therapy may control symptoms without changing all the beliefs and learned patterns associated with the disorder.
Limitation: delayed effects
The client must continue taking medication before improvement can be assessed.
This may be difficult because:
Symptoms remain during the early period.
Side effects may appear before benefits.
The client may stop taking the medication.
The person may incorrectly conclude that it is ineffective.
The delayed response also suggests that the treatment mechanism is more complicated than an immediate correction of serotonin levels.
Limitation: symptom return
Medication changes biological functioning while it is being taken.
If treatment ends, the underlying vulnerability may remain.
Symptoms may return, particularly when:
Medication is stopped suddenly.
Environmental stress remains.
The person has not developed other ways of managing symptoms.
This may mean that medication controls rather than permanently removes the difficulty.
The treatment fallacy
What is the treatment fallacy?
The treatment fallacy occurs when the effectiveness of a treatment is treated as proof of the disorder’s original cause.
For example:
SSRIs reduce OCD symptoms, so OCD must be caused by low serotonin.
This conclusion is not logically justified.
Why the reasoning is flawed
A treatment may alter a system and reduce symptoms without reversing the original cause.
For example:
Painkillers reduce pain.
A lack of painkillers did not cause the pain.
Similarly:
SSRIs increase serotonin activity.
This does not prove that low serotonin originally caused OCD.
Appropriate conclusion
A safer conclusion is:
The effectiveness of SSRIs is consistent with serotonin involvement, but it does not establish that abnormal serotonin was the original or only cause of OCD.
Evaluating the appropriateness of drug therapy
What does appropriateness mean?
Appropriateness concerns whether treatment is suitable for:
A particular client.
Their symptoms.
Their physical health.
Their circumstances.
Their preferences.
The balance of benefits and risks.
A treatment can be effective in research but inappropriate for one individual.
Strength: drug therapy is relatively easy to administer
Medication can normally be taken at home.
It does not require the client to:
Attend several lengthy therapy sessions each week.
Discuss every intrusive thought immediately.
Complete complex psychological tasks.
Confront a feared situation directly.
This may make it suitable for a person whose symptoms make active participation difficult.
Strength: it requires less psychological effort
Severe OCD may involve:
Intense anxiety.
Exhausting rituals.
Poor concentration.
Low mood.
Reduced motivation.
Taking medication may initially require less emotional and cognitive effort than a demanding psychological programme.
Limitation
The client must still:
Remember to take the medication.
Continue despite delayed benefits.
Attend monitoring appointments.
Report side effects.
Follow medical guidance.
It is therefore not completely effort-free.
Strength: medication may be cost-effective
Drug treatment may cost less than a long programme requiring repeated contact with a trained therapist.
Possible economic benefits include:
Fewer therapy hours.
Treatment at home.
Reduced travel.
Quicker access.
Reduced disruption to work or education.
AQA’s June 2025 examiner report identified economic benefits as a useful evaluation point when properly developed.
Qualification
Medication may become costly when:
It is required for a long period.
Several drugs must be tried.
Side effects require further treatment.
Symptoms return after medication stops.
Regular monitoring is necessary.
Cost-effectiveness depends on the whole course of treatment.
Strength: medication is not highly disruptive
A client can often continue:
Working.
Studying.
Caring for family members.
Participating in ordinary activities.
The treatment does not normally require hospital admission.
However, side effects may themselves interfere with daily life.
Limitation: side effects
SSRIs can produce unwanted effects.
Possible side effects include:
Nausea.
Headaches.
Sleep disturbance.
Agitation.
Digestive difficulties.
Sexual dysfunction.
Side effects differ between clients.
They may:
Disappear as the body adjusts.
Continue throughout treatment.
Be sufficiently severe for the client to stop.
Specific rather than generic evaluation
A strong evaluation identifies:
A particular side effect.
The drug type associated with it.
Why it affects appropriateness.
For example:
Sleep disturbance may reduce the suitability of an SSRI for a client whose OCD is already disrupting sleep and concentration.
The June 2025 examiner report noted that specific discussion of medication side effects was more effective than vague reference to drugs being harmful.
Limitation: side effects of alternative drugs
Tricyclic antidepressants may produce:
Drowsiness.
Dry mouth.
Dizziness.
Potential cardiovascular effects.
Benzodiazepines may produce:
Drowsiness.
Reduced alertness.
Tolerance.
Dependence.
These risks may limit their suitability for long-term use.
Limitation: drug interactions and health considerations
Medication may be less appropriate when a client:
Takes other medicines.
Has a relevant physical-health condition.
Is especially vulnerable to a side effect.
Cannot follow a regular dosing routine.
Has previously reacted badly to the drug.
This is why prescription and monitoring require qualified medical professionals.
Limitation: drug therapy is passive
Drug therapy may be described as a passive treatment because the client takes medication rather than actively examining the psychological processes associated with the disorder.
Possible disadvantages include:
Little insight into triggers.
Little understanding of obsessive thinking.
Limited development of coping skills.
Continued dependence on medication.
No direct challenge to beliefs supporting rituals.
Official AQA marking guidance accepts the passive nature of drug treatment and its limited ability to provide insight as evaluation.
A balanced view
Being passive can also be an advantage.
For a client who is severely distressed, a treatment requiring limited initial effort may be more appropriate.
The same feature can therefore be evaluated in two ways:
Passive nature as a strength | Passive nature as a limitation |
Requires less motivation | Develops fewer psychological skills |
Accessible during severe symptoms | Offers limited insight |
Easy to fit around daily life | May create reliance on medication |
Does not require immediate disclosure | Does not directly address beliefs or learned behaviour |
Limitation: informed consent
Clients should understand:
The expected benefits.
Possible side effects.
The delayed response.
How long treatment may continue.
The importance of medical review.
The risks of stopping medication suddenly.
Consent is less meaningful if risks are not explained clearly.
Limitation: adherence
Adherence means following the agreed treatment instructions.
A client may not take medication consistently because:
They forget.
Side effects are unpleasant.
Improvement is delayed.
They feel better and stop.
They do not believe the drug is helping.
The routine is difficult to maintain.
Poor adherence can make an effective drug appear ineffective.
It may also produce fluctuations in symptoms.
Biological explanations and treatment choice
Neural heterogeneity
Different clients may have different neural abnormalities.
One person’s symptoms may be associated mainly with:
Serotonin functioning.
Another person may show greater involvement of:
Dopamine.
Brain-circuit activity.
Psychological learning.
Environmental stress.
This helps explain different treatment responses.
Aetiological heterogeneity
Aetiological heterogeneity means that the same diagnosis may have different causes in different people.
Therefore:
One medication may work well for one client.
The same medication may have little effect for another.
Treatment may require individual adjustment.
Polygenic vulnerability
OCD is thought to involve many possible genes.
Different genetic combinations may influence:
Drug response.
Side effects.
Neurotransmitter functioning.
Symptom patterns.
This supports an individualised rather than one-size-fits-all approach.
Drug therapy and reductionism
Biological reductionism
Drug therapy follows a biologically reductionist approach.
It focuses on components such as:
Serotonin.
Receptors.
Transporters.
Neural circuits.
Advantage
Reductionism allows scientists to:
Identify measurable mechanisms.
Test drugs systematically.
Measure symptom change.
Develop targeted treatments.
Disadvantage
It may overlook:
The meaning of obsessive thoughts.
Environmental stress.
Learning.
Reinforcement of compulsions.
Family experiences.
The client’s beliefs.
Changing serotonin activity may not remove every psychological process maintaining the disorder.
Drug therapy and determinism
A strongly biological account may suggest that OCD is controlled entirely by:
Genes.
Neurotransmitters.
Brain activity.
This is biological determinism.
The success of psychological change and variation between clients suggests that biology influences rather than completely determines the disorder.
Medication should therefore be understood as one possible treatment rather than proof that the person has no control or capacity for change.
Drug therapy and client choice
Appropriateness should include the client’s preferences.
One client may prefer medication because:
It is private.
It fits around work.
They find discussion difficult.
They want rapid access to treatment.
Another may prefer not to take medication because:
They are concerned about side effects.
They want greater understanding of their symptoms.
They have had a previous adverse reaction.
They dislike taking medication long term.
The same treatment may therefore be appropriate for one person and inappropriate for another.
Evaluating evidence for drug therapy
Randomised controlled trials
A drug may be tested using a randomised controlled trial.
Participants are randomly allocated to:
The drug condition.
A placebo condition.
Another treatment condition.
What is a placebo?
A placebo is an inactive treatment designed to resemble the real drug.
Comparing a drug with a placebo helps estimate whether improvement exceeds:
Expectation.
Natural recovery.
Attention from medical professionals.
Repeated measurement.
Double-blind procedure
In a double-blind procedure:
Participants do not know which treatment they receive.
Researchers interacting with them do not know which condition they are in.
This reduces:
Participant expectations.
Researcher bias.
Differences in treatment between groups.
Ethical considerations
Researchers must consider:
Informed consent.
Monitoring of side effects.
Protection from harm.
The treatment available to the placebo group.
The right to withdraw.
Problems with placebo studies
Placebo effects
A participant may improve because they expect treatment to work.
This does not mean the improvement is imagined.
Expectations can influence:
Anxiety.
Attention.
Reporting of symptoms.
Behaviour.
Side effects may reveal the condition
A participant experiencing recognisable side effects may correctly guess that they received the real drug.
This could reduce the effectiveness of the blind procedure.
Self-report limitations
Drug trials often use questionnaires or interviews.
Participants may:
Underreport symptoms.
Overstate improvement.
Want to please the researcher.
Use rating scales differently.
Behavioural and functional outcomes should also be measured.
Attrition
Attrition occurs when participants leave a study.
People experiencing severe side effects may be especially likely to withdraw.
If only those who tolerate the medication remain, the final results may exaggerate:
Effectiveness.
Acceptability.
Safety.
Completion rates should therefore be reported.
Interpreting treatment data
Suppose researchers record mean OCD symptom scores.
Higher scores indicate more severe symptoms.
Group | Before treatment | After treatment | Three-month follow-up |
SSRI | 28.4 | 15.2 | 16.1 |
Placebo | 28.0 | 23.9 | 23.4 |
A careful interpretation would state:
Both groups began with similar symptom scores.
The SSRI group showed a larger reduction.
Most of the reduction remained at follow-up.
The placebo group showed a smaller improvement.
The pattern is consistent with the SSRI being effective.
However, the table does not show:
Sample size.
Individual differences.
Statistical significance.
Side effects.
Attrition.
Adherence.
How treatment allocation occurred.
The data support a conclusion but do not prove it alone.
Applying drug therapy to unfamiliar scenarios
Scenario 1: intrusive checking thoughts
Oliver repeatedly worries that his cooker has been left switched on.
He checks it several times and is often late for work.
A biological treatment may involve an SSRI.
The drug would:
Inhibit serotonin reuptake.
Increase serotonin availability.
Continue postsynaptic stimulation.
Potentially reduce Oliver’s anxiety and persistent doubts.
Potentially reduce repeated checking.
Scenario 2: delayed benefit
Meera has taken an SSRI for ten days and stops because she believes it is ineffective.
A psychologist could explain that:
SSRIs do not normally produce full benefit immediately.
Treatment may require several weeks of consistent use.
Stopping early prevents a fair assessment of effectiveness.
Any medication decision must be reviewed with the prescriber.
Scenario 3: side effects
Calum’s obsessive thoughts become less severe after taking an SSRI, but he experiences significant sleep disturbance.
This illustrates a difference between:
Effectiveness: symptoms have improved.
Appropriateness: the side effect may make the medication unsuitable.
A treatment can be effective but still require review because it is not appropriate for that client.
Scenario 4: lack of response
Anya takes an SSRI consistently for an appropriate period but experiences little change.
This may suggest that:
The drug is not effective for Anya.
Her symptoms may involve a different biological pathway.
OCD is aetiologically heterogeneous.
Another drug or treatment may be considered.
It does not prove that serotonin has no role in any case of OCD.
Scenario 5: preference for medication
Hassan finds discussing his intrusive thoughts extremely difficult but is willing to take medication and attend monitoring appointments.
Drug therapy may be appropriate because:
It does not initially require detailed discussion.
It can be taken at home.
It may reduce distress enough to improve daily functioning.
However, the possible side effects and delayed response must still be explained.
Scenario 6: medication and biological explanations
A researcher finds that an SSRI reduces symptoms in some participants but not others.
The result:
Supports serotonin involvement because some participants improve.
Challenges a universal serotonin explanation because others do not.
Supports aetiological heterogeneity.
Does not prove that low serotonin caused the disorder.
Distinguishing explanation and treatment in scenarios
Suppose a scenario states:
“A client has reduced serotonin activity and is prescribed fluoxetine.”
The reduced serotonin activity is:
Part of a neural explanation.
Fluoxetine is:
An SSRI treatment.
The inhibition of serotonin reuptake is:
The treatment mechanism.
The reduction in obsessive thoughts is:
The intended outcome.
Keeping these stages separate makes an answer clearer.
Answering description questions
Two-mark question
A brief response could include:
The name of the drug type.
Its effect at the synapse.
Useful structure:
SSRIs inhibit the reuptake of serotonin into the presynaptic neuron, leaving more serotonin available to continue stimulating the postsynaptic neuron.
Four-mark question
A four-mark description may require:
The role of serotonin.
How an SSRI affects reuptake.
Increased serotonin availability.
Reduction of OCD symptoms.
Do not spend all four marks naming different drugs without explaining how they work.
Link questions
When asked to link treatment with an explanation:
Identify the biological abnormality.
Explain the treatment mechanism.
Explain how the mechanism may reduce symptoms.
For example:
Neural explanations associate OCD with abnormal serotonin transmission. SSRIs inhibit serotonin reuptake, increasing serotonin activity at the synapse. This may improve the regulation of anxiety and obsessive thoughts, reducing compulsive behaviour.
Answering evaluation questions
Effectiveness paragraph
A strength of drug therapy is that SSRIs reduce symptoms for many clients by increasing serotonin availability at the synapse. This supports serotonergic involvement and may improve everyday functioning. However, not every client responds, suggesting that OCD has different causes and that one neurotransmitter explanation is incomplete.
Side-effects paragraph
A limitation is that SSRIs can produce side effects such as nausea, sleep disturbance and sexual dysfunction. A medication may reduce compulsions but still be inappropriate if its side effects seriously interfere with daily life. Effectiveness must therefore be balanced against acceptability.
Cost paragraph
Drug therapy may be cost-effective because tablets can be taken at home and require less therapist time than a lengthy psychological programme. However, long-term prescription, monitoring and treatment of side effects may reduce this economic advantage.
Treatment-fallacy paragraph
Improvement after an SSRI is consistent with serotonin involvement, but it does not prove that low serotonin caused OCD. Medication may alter a system that maintains symptoms without reversing the original cause. Drug effectiveness therefore provides indirect rather than conclusive support for neural explanations.
Passive-treatment paragraph
Drug therapy requires relatively little psychological effort, making it suitable for clients experiencing severe anxiety or low motivation. However, its passive nature means that clients may gain little understanding of their obsessions or develop few independent coping skills.
Planning an extended response
A strong extended response could follow this structure:
Introduce drug therapy as a biological treatment.
Explain the role of serotonin.
Describe normal synaptic transmission.
Explain how SSRIs inhibit reuptake.
Explain continued postsynaptic stimulation.
Link the mechanism to reduced OCD symptoms.
Outline alternative drugs.
Link treatment with neural explanations.
Link treatment with genetic vulnerability.
Use evidence of symptom reduction as support.
Discuss variation in treatment response.
Explain side effects.
Discuss delayed effects.
Explain the treatment fallacy.
Evaluate cost and convenience.
Discuss the passive nature of treatment.
Consider individual differences and client choice.
Reach a balanced conclusion.
A balanced assessment
Drug therapy has several important strengths:
SSRIs have a clear biological mode of action.
Medication can reduce OCD symptoms for many clients.
It may improve everyday functioning.
It is relatively easy to administer.
It usually requires less psychological effort.
It can be more accessible and economical than lengthy treatment.
It provides indirect support for serotonin involvement.
However:
It does not work for everyone.
Benefits may be incomplete or delayed.
Side effects can reduce appropriateness.
Alternative drugs may produce more serious risks.
Adherence may be difficult.
The treatment is relatively passive.
It may provide little insight or development of coping skills.
Drug effectiveness does not prove biological causation.
Different clients may have different causes and treatment needs.
The most justified conclusion is:
Drug therapy can be an effective and appropriate treatment for many people with OCD, particularly when symptoms are severe or active psychological participation is difficult. Its usefulness depends on individual response, side effects, monitoring and informed client choice. It is best understood as a treatment targeting one part of a complex disorder rather than proof that every case of OCD is caused by a single serotonin imbalance.
Key Words 🔑
Key word | Student-friendly definition | How it may be used in an exam |
Drug therapy | The use of medication to alter biological processes and reduce symptoms. | Introduce the biological treatment of OCD. |
Selective serotonin reuptake inhibitor | A drug that reduces the reabsorption of serotonin into the presynaptic neuron. | Explain the main drug treatment. |
SSRI | Abbreviation for selective serotonin reuptake inhibitor. | Use after defining the full term. |
Serotonin | A neurotransmitter involved in mood, anxiety and behavioural regulation. | Link drug therapy with neural explanations. |
Neurotransmitter | A chemical messenger carrying signals between neurons. | Explain the biological mechanism. |
Synapse | The small gap between two neurons. | Describe where an SSRI acts. |
Presynaptic neuron | The neuron that releases a neurotransmitter. | Explain serotonin release and reuptake. |
Postsynaptic neuron | The neuron containing receptors that receive the neurotransmitter. | Explain continued stimulation. |
Reuptake | Reabsorption of a neurotransmitter into the presynaptic neuron. | Explain the process inhibited by SSRIs. |
Serotonin transporter | A protein that carries serotonin back into the presynaptic neuron. | Explain the target of an SSRI. |
Fluoxetine | An example of an SSRI. | Give a relevant treatment example. |
Tricyclic antidepressant | An older antidepressant affecting neurotransmitter reuptake. | Explain an alternative to SSRIs. |
Clomipramine | A tricyclic antidepressant associated with OCD treatment. | Give an example of an alternative drug. |
Serotonin-noradrenaline reuptake inhibitor | A drug reducing the reuptake of serotonin and noradrenaline. | Outline another alternative. |
SNRI | Abbreviation for serotonin-noradrenaline reuptake inhibitor. | Use after defining the full term. |
Benzodiazepine | A drug that may reduce anxiety and promote relaxation. | Explain one anxiety-reducing alternative. |
Side effect | An unintended effect produced by treatment. | Evaluate appropriateness. |
Adherence | The extent to which a client follows treatment instructions. | Evaluate delayed treatment and daily medication. |
Placebo | An inactive treatment designed to resemble the real treatment. | Evaluate drug research. |
Double-blind procedure | A procedure in which participants and relevant researchers do not know treatment allocation. | Explain control of expectations and bias. |
Attrition | Participants leaving a study before it is completed. | Evaluate treatment evidence. |
Effectiveness | The extent to which treatment produces meaningful improvement. | Discuss symptom reduction and functioning. |
Appropriateness | The extent to which treatment is suitable for a particular client. | Discuss side effects, preference and health. |
Treatment fallacy | Incorrectly treating an effective therapy as proof of a disorder’s cause. | Evaluate biological support from medication. |
Aetiological heterogeneity | The same disorder having different causes in different people. | Explain variation in drug response. |
Passive treatment | A treatment requiring relatively little active psychological participation. | Evaluate ease of use and lack of insight. |
Biological reductionism | Explaining complex behaviour mainly through biological components. | Evaluate the treatment’s narrow focus. |
Hints from the Examiner Reports 💡
Examiner hint: Explain exactly how an SSRI works. Strong answers describe serotonin reuptake being inhibited so that serotonin remains in the synapse and continues stimulating the postsynaptic neuron.
Examiner hint: Do not state that SSRIs create serotonin or release unlimited amounts of it. They mainly reduce reuptake of serotonin that has already been released.
Examiner hint: Keep treatment and explanation separate. The Autumn 2021 report noted that many students described biological explanations of OCD when the question asked how OCD was treated.
Examiner hint: Read the command word carefully. A description question requires the treatment process, while a discussion question also requires evidence, strengths, limitations and judgement.
Examiner hint: Do not write only that drugs “balance chemicals”. Identify the neurotransmitter and describe the synaptic mechanism.
Examiner hint: Strong evaluation is specific. Name the drug category, the side effect or the treatment feature, and explain why it affects effectiveness or appropriateness.
Examiner hint: Distinguish effectiveness from appropriateness. A drug can reduce symptoms but still be unsuitable because of side effects.
Examiner hint: Use treatment evidence cautiously. SSRI success supports serotonin involvement, but the treatment fallacy means it does not prove that low serotonin caused OCD.
Examiner hint: Consider clients who do not improve. Variation in response suggests that one drug and one biological abnormality cannot explain every case.
Examiner hint: Avoid lengthy generic research criticism. AQA’s June 2025 report advised students to link evaluation directly to neural mechanisms or drug treatment rather than presenting unrelated methodological points.
The Autumn 2021 examiner report praised students who described the synaptic action of SSRIs accurately. It also identified confusion about how the drugs worked as a common error.
Common Mistakes ⚠️
Mistake: Saying SSRIs increase serotonin production
Why this is inaccurate:
Their central action is to inhibit serotonin reuptake.
How to improve:
Explain that serotonin remains available in the synapse for longer.
Mistake: Saying SSRIs stop serotonin being released
Why this is incorrect:
Serotonin must be released before it can cross the synapse.
How to improve:
State that SSRIs reduce its reabsorption after release.
Mistake: Saying SSRIs block postsynaptic receptors
Why this is incorrect:
The treatment allows serotonin to continue stimulating those receptors.
How to improve:
Refer to blocking or inhibiting the reuptake transporter.
Mistake: Saying the postsynaptic neuron reabsorbs serotonin
Why this is inaccurate:
Reuptake returns serotonin to the presynaptic neuron.
How to improve:
Learn the direction of transmission carefully.
Mistake: Describing serotonin as a “happy chemical”
Why this is oversimplified:
Serotonin contributes to several processes, including anxiety and behavioural regulation.
How to improve:
Use precise psychological terminology.
Mistake: Saying low serotonin definitely causes OCD
Why this is too deterministic:
Serotonin is one possible contributor within a complex disorder.
How to improve:
Use terms such as associated with, may contribute to and vulnerability.
Mistake: Writing only about the neural explanation
Why this does not answer a treatment question:
It explains why OCD may develop but not how medication reduces symptoms.
How to improve:
Link the explanation to the SSRI mechanism.
Mistake: Describing genetic explanations for most of the answer
Why this loses focus:
The question asks about medication rather than inherited vulnerability.
How to improve:
Use genes briefly to explain the biological rationale.
Mistake: Saying SSRIs work immediately
Why this is inaccurate:
Noticeable symptom reduction usually requires continued treatment.
How to improve:
Refer to delayed improvement and regular daily use.
Mistake: Concluding that a drug is ineffective after a few days
Why this is premature:
The treatment needs an appropriate period before its effect can be judged.
How to improve:
Explain the delayed timescale.
Mistake: Naming fluoxetine without explaining how it works
Why this gains limited credit:
A drug name alone does not demonstrate understanding.
How to improve:
Describe reuptake inhibition and postsynaptic stimulation.
Mistake: Listing several drugs with no detail
Why this is weak description:
The examiner needs the biological mechanism.
How to improve:
Develop SSRIs fully before adding alternatives.
Mistake: Treating SSRIs and SNRIs as identical
Why this is inaccurate:
SSRIs primarily target serotonin, while SNRIs target serotonin and noradrenaline.
How to improve:
Use the full names to remember the distinction.
Mistake: Saying tricyclics have no disadvantages
Why this is incorrect:
They may produce more severe side effects than SSRIs.
How to improve:
Explain why they are commonly treated as an alternative rather than a simple first choice.
Mistake: Saying benzodiazepines permanently cure OCD
Why this is inaccurate:
They may reduce general anxiety but do not remove every cause or symptom.
How to improve:
Describe their limited, anxiety-reducing role.
Mistake: Saying treatment success proves low serotonin caused OCD
Why this is the treatment fallacy:
Changing a system can reduce symptoms without identifying the original cause.
How to improve:
Describe drug response as indirect support.
Mistake: Ignoring clients who do not respond
Why this weakens evaluation:
Treatment effectiveness varies.
How to improve:
Use non-response to discuss aetiological heterogeneity.
Mistake: Saying drug therapy is always appropriate because it is easy
Why this is too absolute:
Side effects, health conditions and preferences differ.
How to improve:
Balance ease of administration against individual risks.
Mistake: Saying passive treatment is entirely negative
Why this is one-sided:
Limited effort may help a person with severe symptoms.
How to improve:
Evaluate passivity as both a strength and a limitation.
Mistake: Giving vague side-effect evaluation
Why this gains limited credit:
“Drugs can be bad for you” lacks psychological detail.
How to improve:
Name a relevant side effect and explain its impact on suitability.
Mistake: Confusing effectiveness with appropriateness
Why this is incorrect:
A treatment can work but still be unsuitable.
How to improve:
Use symptom reduction for effectiveness and client suitability for appropriateness.
Mistake: Assuming placebo improvement proves the drug does not work
Why this is incorrect:
The important comparison is whether the drug group improves more than the placebo group.
How to improve:
Compare the size of change in both conditions.
Mistake: Ignoring attrition in drug research
Why this may exaggerate effectiveness:
People experiencing severe side effects may leave the study.
How to improve:
Consider whether final results include all participants.
Mistake: Claiming tablets directly change irrational beliefs
Why this is inaccurate:
Medication primarily alters biological functioning.
How to improve:
Explain that reduced anxiety may make thoughts less distressing without directly disputing their content.
Exam-Style Questions ✍️
Question 1
Which one of the following best describes the action of a selective serotonin reuptake inhibitor?
A. It prevents serotonin from being released
B. It reduces the reabsorption of serotonin into the presynaptic neuron
C. It destroys postsynaptic serotonin receptors
D. It reduces the amount of serotonin within the synapse
[1 mark]
Question 2
Define reuptake in the context of synaptic transmission.
[2 marks]
Question 3
Explain how an SSRI may reduce symptoms of OCD.
[4 marks]
Question 4
Outline one alternative to an SSRI that may be used in the biological treatment of OCD.
[3 marks]
Question 5
Amira has taken an SSRI for one week and says that it cannot work because her checking rituals have not yet changed.
Use your knowledge of drug therapy to explain why Amira’s conclusion may be premature.
[4 marks]
Question 6
Leon experiences fewer obsessive thoughts after taking an SSRI, but the medication also causes severe sleep disturbance.
Use this example to explain the difference between the effectiveness and appropriateness of a treatment.
[4 marks]
Question 7
Researchers record mean OCD symptom scores. Higher scores indicate more severe symptoms.
Group | Before treatment | After treatment |
SSRI | 29.1 | 15.8 |
Placebo | 28.7 | 23.6 |
Describe the pattern shown in the table. Explain one conclusion and one limitation of the results.
[6 marks]
Question 8
A researcher claims:
“SSRIs reduce OCD symptoms, so OCD must be caused by low serotonin.”
Explain why this conclusion may involve the treatment fallacy.
[4 marks]
Question 9
Explain one strength and one limitation of drug therapy as a treatment for OCD.
[6 marks]
Question 10
Discuss the appropriateness and effectiveness of drug therapy as a treatment for obsessive-compulsive disorder.
[8 marks]
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