What causes depression and anxiety disorders, and how are they treated?
Depression or anxiety: symptoms and diagnosis, biological and cognitive explanations, drug and psychological treatments, and the named studies for the chosen second disorder.
An Edexcel A-Level Psychology answer to the second clinical disorder, covering the symptoms and diagnosis of depression (and OCD as an anxiety option), biological and cognitive explanations including Beck and Ellis, drug and CBT treatments, GRAVE evaluation and named studies.
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What this dot point is asking
Edexcel requires a second disorder besides schizophrenia, usually depression (or an anxiety disorder such as OCD or a phobia). You must describe its symptoms and diagnosis, explain it biologically and cognitively, and evaluate its biological and psychological treatments using named studies.
The answer
Symptoms and diagnosis
For the anxiety option, obsessive-compulsive disorder (OCD) involves recurrent intrusive obsessions (anxiety-provoking thoughts) and repetitive compulsions (behaviours that reduce the anxiety), while a phobia involves an excessive, persistent fear of a specific object or situation with avoidance.
Biological explanations
Cognitive explanations
Treatments
Biological treatment uses antidepressant drugs, especially SSRIs (selective serotonin reuptake inhibitors, such as fluoxetine), which block the reuptake of serotonin at the synapse, raising its availability and lifting mood over several weeks. SSRIs are also first-line for OCD.
Psychological treatment uses CBT (cognitive behavioural therapy). The cognitive element identifies and challenges negative automatic thoughts and irrational beliefs, replacing them with realistic ones; the behavioural element uses behavioural activation (re-engaging in rewarding activity) for depression and exposure with response prevention (ERP) for OCD.
Evaluation (GRAVE)
- Generalisability. Many treatment trials use specific clinical samples and Western diagnostic criteria, so findings may not generalise across cultures or to patients with comorbid disorders.
- Reliability. Standardised symptom measures (the Beck Depression Inventory) and manualised CBT make studies replicable, supporting reliable comparison of treatments.
- Application. Both explanations have produced effective, widely used treatments (SSRIs and CBT), and combining them often outperforms either alone, a clear real-world benefit.
- Validity. The cause-and-effect direction is unclear: negative thinking and low serotonin may be symptoms rather than causes of depression, weakening both explanations.
- Ethics. SSRIs carry side effects (and a debated link to increased suicidal thoughts in young people early in treatment), so prescribing must be monitored, while CBT can imply patients are to blame for their own thinking.
Examples in context
Example 1. SSRIs and the reuptake mechanism. Fluoxetine (Prozac) selectively blocks the serotonin transporter that normally reabsorbs serotonin from the synaptic gap back into the presynaptic neuron. By preventing reuptake, more serotonin remains in the synapse to repeatedly stimulate the postsynaptic receptors. Clinically, the delayed onset (mood lifts only after two to four weeks) despite immediate reuptake blockade is an important evaluation point: it suggests the monoamine hypothesis is incomplete and that downstream changes in receptor sensitivity and neuroplasticity matter. This is the kind of mechanistic and evaluative detail that earns AO3 marks.
Example 2. CBT for OCD with exposure and response prevention. A patient with contamination obsessions and a hand-washing compulsion is treated with ERP. The cognitive element challenges the irrational belief that not washing will cause harm; the behavioural element exposes the patient to a feared trigger (touching a door handle) while preventing the compulsive response (washing). Anxiety initially rises but then falls naturally (habituation), teaching the patient that the feared consequence does not occur and that the compulsion is unnecessary. Trials show ERP-based CBT is highly effective for OCD, often combined with an SSRI, illustrating an interactionist, combined-treatment approach.
Try this
Q1. Describe Beck's cognitive explanation of depression. [4 marks]
- Cue. Beck argued depression arises from negative schemas and the cognitive triad (pessimistic, irrational views of the self, the world and the future), plus cognitive biases such as overgeneralisation that distort information processing.
Q2. Explain how SSRIs work as a treatment for depression. [3 marks]
- Cue. SSRIs block the reuptake of serotonin at the synapse, raising its availability and prolonging its action on postsynaptic receptors, which lifts mood over several weeks.
Q3. Evaluate the use of CBT compared with drug therapy for depression. [8 marks]
- Cue. CBT addresses maintaining thoughts and gives lasting skills with no physical side effects but needs effort and may suit milder cases; drugs act faster with little effort but have side effects and treat symptoms; conclude that combined treatment is usually most effective.
Exam-style practice questions
Practice questions written in the style of Pearson Edexcel exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Edexcel 20198 marksDescribe and evaluate the cognitive explanation of depression. [8 marks]Show worked answer →
This is split AO1 (description) and AO3 (evaluation), so cover both.
AO1 description (about half the marks). Beck argued depression arises from negative schemas formed in childhood, the cognitive triad (negative views of the self, the world and the future), and cognitive biases such as overgeneralisation and catastrophising. Ellis's ABC model says an activating event (A) is interpreted through irrational beliefs (B), producing emotional consequences (C); it is the belief, not the event, that causes depression.
AO3 evaluation. Strengths: strong research support (negative thinking predicts depression), and it has led to an effective treatment, CBT, giving practical application. Weaknesses: cause and effect is unclear, as negative thinking may be a symptom rather than a cause; it is reductionist, downplaying biological factors (serotonin) and life events; and it can imply blame on the patient for their own thinking.
Markers reward a clear account of Beck (triad, schemas, biases) and Ellis (ABC), then at least two evaluation points, with a judgement (best combined with biological factors).
Edexcel 20226 marksIn a trial, mean Beck Depression Inventory scores fell from before CBT to after, with standard deviations of before and after. Calculate the mean reduction and explain what the change in standard deviation suggests about how patients responded. [6 marks]Show worked answer →
A quantitative item: show the calculation (AO2) then interpret (AO3).
Mean reduction: points on the Beck Depression Inventory, so on average symptoms fell substantially after CBT.
Interpreting the standard deviations (SD measures spread around the mean): the SD rose from to . Before treatment, scores clustered tightly (most patients were similarly, severely depressed). After treatment, scores were much more spread out, which suggests CBT worked very well for some patients (large drops) but much less for others (small or no change). This is individual variation in treatment response.
The larger post-treatment spread is a warning against concluding CBT works equally for everyone, and supports offering combined or alternative treatments for non-responders. An inferential test (such as a Wilcoxon, related design) would be needed to confirm the reduction is significant.
Markers reward the correct reduction (12), a correct definition of SD as dispersion, and the interpretation that the larger post-treatment SD shows variable individual response.
Related dot points
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An Edexcel A-Level Psychology answer to the key studies and classic research, covering the named classic studies (Milgram, Sherif, Baddeley, Watson and Rayner, Raine, Rosenhan), how to evaluate methodology and ethics with GRAVE, and how to review and synthesise evidence for Paper 3.
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Sources & how we know this
- Pearson Edexcel A-Level Psychology (9PS0) specification — Pearson Edexcel (2015)