Providing psychotherapy at 50 sessions in a year (starting twice weekly) led to faster and greater improvements in depression and personality functioning compared to 25 sessions, starting weekly for patients with depression and personality disorder (PD). This study reports long-term dosage effects at 18 and 24 months.

In a pragmatic, double-randomized clinical trial, 246 outpatients with depression and PD were assigned to (1) 25 or 50 sessions and (2) Short-term Psychodynamic Supportive Psychotherapy (SPSP) or Schema Therapy (ST). Depression severity was assessed with the Beck Depression Inventory-II. Secondary outcomes included diagnostic remission of depression (MINI-plus), PD (SCID-II/SCID-5-P), and treatment-specific measures. Intention-to-treat analyses were conducted.

At 18 and 24 months, BDI-II means did not differ between dosage groups (19.0 for 25 sessions versus 19.1 for 50 sessions; d = −0.01; 95% CI = −0.35-0.37, p = 0.96). The lower-dosage group improved during follow-up (−2.6 BDI points, p = 0.031), which may be partly attributed to additional therapy received by a subgroup. Remission rates at 24 months were 66% for depression and 76% for PD, with no differences between conditions.

Higher psychotherapy dosage led to faster initial improvements, but long-term outcomes were not superior to those achieved with a lower dosage. These results should be interpreted with caution, as unregulated treatment during follow-up reduced the power to detect significant dosage effects. Both SPSP and ST provide viable alternatives to treatments focused solely on depression.

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

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.

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.

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

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

Time-limited psychotherapy for depression is effective. However, comorbid personality disorders affect therapy outcomes negatively. Studies of follow-up effects and results relating to the influence of comorbid personality disorder and treatment modality are scarce.

To determine the influence of comorbid personality disorder and treatment modality on outcomes after cognitive–behavioural therapy (CBT) or short-term psychodynamic supportive psychotherapy (SPSP) for depression.

This study draws on data from a previously published randomised clinical trial contrasting SPSP and CBT for depression (both 16 sessions). We compared the effectiveness of these psychotherapies for patients with and without personality disorder (n = 196). The primary measure was depression outcome; the secondary measurements were interpersonal functioning and quality of life. Collected data were analysed using multilevel analysis. Trial registration: ISRCTN31263312 (http://www.controlled-trials.com).

Although participants with and without comorbid personality disorder improved at treatment termination (d = 1.04, 95% CI 0.77–1.31 and d = 1.36, 95% CI 0.97–1.76, respectively) and at follow-up (d = 1.15, 95% CI 0.87–1.43 and d = 2.12, 95% CI 1.65–2.59 respectively), personality disorder had a negative effect on depression outcome at both measurement points (P < 0.05). A similar negative effect on interpersonal functioning was no longer apparent at follow-up. Comorbid personality disorder had no influence on social functioning or quality of life outcomes, irrespective of treatment modality.

CBT and SPSP contribute to the improvement of depressive symptoms and interpersonal problems in depressed patients with and without comorbid personality disorder. Both treatments are an effective first step in a stepped care approach, but – given remaining levels of depression in patients with personality disorder – they are probably inadequate for large numbers of patients with this comorbidity.

None.