This is an unusual randomised controlled trial conducted by a research team from Arkin Institute for Mental Health in Amsterdam and funded by Eli Lilly. The study measures social functioning as an outcome, as well as the more commonly measured depression symptoms. It aims to find out how much psychotherapy is optimal for depressed people who are also taking antidepressants.

The trial involved 463 adults living in the community with a DSM-IV diagnosis of depression and a baseline score ≥14 on the Hamilton Depression Rating Scale. The researchers put together a sensible set of exclusion criteria.

Participants were randomly assigned to either:

1. 8 (45 min) weekly sessions of short psychodynamic supportive psychotherapy, combined with usual antidepressant treatment (fluoxetine, nortriptyline or mirtazapine)
2. 8 (45 min) weekly sessions of short psychodynamic supportive psychotherapy, followed by 8 (45 min) fortnightly sessions of short psychodynamic supportive psychotherapy, combined with usual antidepressant treatment

The authors did not state that allocation of patients to treatment arms was concealed.

The outcomes of interest were:

• Improvement in social functioning score at 20 weeks (Groningen Social Disability Scale, GSDS)
• Change in severity of depression at week 24 (17-item HDRS score, clinical global impression of severity and improvement (CGI-S), the depression subscale of the ninety symptom checklist (SCL-90), and the Quality of Life Depression Scale)

All patients were followed up for 24 weeks and the following results were found:

• Social functioning improved significantly by week 20 on 6 of the 11 GSDS sub scales:
• Self-care (p=0.005)
• Citizen role (p=0.001)
• Home/cohabiting (p=0.003)
• Relationship with parents (p=0.012)
• Housekeeping (p=0.001)
• Leisure time (p=0.000)
• However, there was no significant difference between 8 and 16 psychotherapy sessions in social functioning at week 20 (p≥0.1 for all 11 GSDS subscales)
• There was also no significant difference between 8 and 16 psychotherapy sessions in improvement of depression severity on any scale at week 24 (p≥0.3 for HDRS, SCL-90, GCI-S and QLDS)
• Last observation carried forward analysis showed similar results, with no differences between groups

The authors conclude:

At the end of treatment, no clear differences are found between 8 or 16 sessions of psychotherapy – both combined with pharmacotherapy – with regard to severity of depression and social functioning. It is thus still unknown if patients with major depression show more improvement in social functioning and less symptoms of depression after 16 sessions of combined therapy than after 8 sessions. Currently, it seems that for major depression 8 sessions of combined therapy are equally effective as 16 sessions.

Molenaar PJ, Boom Y, Peen J, Schoevers RA, Van R, Dekker JJ. Is there a dose-effect relationship between the number of psychotherapy sessions and improvement of social functioning? Br J Clin Psychol. 2011 Sep;50(3):268-82. doi: 10.1348/014466510X516975. Epub 2011 Mar 8. [PubMed abstract]