Wiles' Study of the Effectiveness of CBT (AQA GCSE Psychology): Revision Note

Antidepressant medications compared to CBT to treat depression

• For some people antidepressant medications alone are not a suitable treatment for depression (known as ‘treatment resistant’)

  • Treatment-resistant depression means a patient has been taking antidepressant medication for more than six weeks and still shows symptoms of clinical depression

• CBT plus antidepressant medication (rather than CBT as a standalone alternative) is a more holistic approach to treating depression, as it addresses the whole person rather than just the physical/biological aspect

• Antidepressants work to reduce the symptoms of depression while CBT works to re-frame irrational thoughts and behaviours around depression

  • Combining them may increase effectiveness because the two approaches complement each other

• Wiles et al. (2013) instigated CoBalT to investigate the efficacy of combined drug and CBT therapies as follows:

  • Aim: to investigate how effective combined therapy is for people with depression who are treatment-resistant

  • Sample: 469 treatment-resistant patients with depression from Bristol, Exeter and Glasgow, recruited via 73 different GP practices

  • Procedure: the patients were randomly allocated to one of the following two conditions:

    • Condition 1: Usual care (each patient continued to take the antidepressant they had been prescribed)

    • Condition 2: Usual care + CBT (their usual antidepressant plus 12-18 sessions of CBT lasting an hour per session)

  • The patients’ symptoms were measured using Beck’s Depression Inventory (BDI)

  • Results: 

    • At 6 months (422 participants, 90%, remaining): Condition 1 — 21.6% had a 50%+ drop in symptoms; Condition 2 — 46.1% had a 50%+ drop

    • At 12 months (396 participants, 84%, remaining): Condition 2 continued to show much greater levels of recovery and a greater chance of remission (symptoms not returning) than Condition 1

  • Conclusions: Combined therapy of drugs + CBT is more effective in reducing depressive symptoms than drug therapy alone, and these benefits can be maintained over 12 months

Evaluation of Wiles’ study of the effectiveness of CBT

Strengths

• The study was well-designed to control extraneous variables: it used an independent groups design with participants randomly allocated to conditions (reducing the risk that one group happened to be more depressed to start with)

  • This ensures that the change in the dependent variable wasn't due to a key extraneous variable, increasing validity

• The study has strong real-world application: it demonstrated in a well-controlled trial that combined therapy can succeed where antidepressants alone fail for two-thirds of people with depression

Weaknesses

• The study relies on self-report (the BDI) to assess depression, which involves subjective judgement

  • Participants may under- or over-report how sad they feel (e.g. social desirability bias, with some playing down their symptoms), questioning the validity of the findings