Dosage effects of psychodynamic and schema therapy in people with comorbid depression and personality disorder: four-arm pragmatic randomised controlled trial.

Background: Higher intensity of psychotherapy might improve treatment outcome in depression, especially in those with comorbid personality disorder.

Aims: To compare the effects of 25 individual sessions (weekly) of two forms of psychotherapy - short-term psychoanalytic supportive psychotherapy (SPSP) and schema therapy - with the same treatments given for 50 sessions (twice weekly) in people with depression and personality disorder. Trial registration: NTR5941.

Method: We conducted a pragmatic, double-randomised clinical trial and, over 37 months, recruited 246 adult out-patients with comorbid depression/dysthymia and personality disorder. A 2 × 2 factorial design randomised participants to 25 or 50 sessions of SPSP or schema therapy. The primary outcome was change in depression severity over 1 year on the Beck Depression Inventory II (BDI-II). Secondary outcomes were remission both of depression and personality disorder.

Results: Compared with 25 sessions, participants who received 50 sessions showed a significantly greater decrease in depressive symptoms over time (time × session dosage, < 0.001), with a mean difference of 5.6 BDI points after 1 year ( -0.53, 95% CI -0.18 to 0.882, = 0.003). Remission from depression was also greater in the 50-session group (74% 58%, = 0.025), as was remission of personality disorder (74% 56%, 0.010).

Conclusions: Greater intensity of psychotherapy leads to better outcomes of both depression and personality status in people with comorbid depression and personality disorder.