Background: Interpersonal psychotherapy and cognitive-behavioural therapy are widely accepted as effective treatments for major depression. There is little evidence on how personality disorder or personality traits affect treatment response.
Aims: To determine whether personality disorder or traits have an adverse impact on treatment response to interpersonal psychotherapy or cognitive-behavioural therapy in people receiving out-patient treatment for depression.
Method: The study was a randomised trial in a university-based clinical research unit for out-patients with depression.
Results: Personality disorder did not adversely affect treatment response for patients with depression randomised to cognitive-behavioural therapy. Conversely, personality disorder did adversely affect treatment response for patients randomised to interpersonal psychotherapy.
Conclusions: Despite the two therapies having comparable efficacy in patients with depression, response to interpersonal psychotherapy (but not cognitive-behavioural therapy) is affected by personality traits. This could suggest the two therapies are indicated for different patients or that they work by different mechanisms.