The results of a previous randomized trial showed that mentalization-based treatment for psychotic disorder (MBTp) was associated with greater improvement than treatment as usual (TAU) in social functioning up to 6 months after treatment. The purpose of the present study is to examine the effect after 5 years.

The researchers tried to find all patients who had participated in the trial (n = 84) and to assess, blind to previous treatment status, their social functioning and mentalizing capacity. Social functioning was measured using the Social Functioning Scale, mentalizing using the Social Cognition and Object Relations Scale and the Hinting Task.

Twenty-three MBTp patients and 23 TAU patients collaborated. There was no evidence of selective drop-out. A complete case, repeated measure analysis of variance on the basis of intention-to-treat showed that, 5 years post-treatment, MBTp patients still scored better on social functioning compared to baseline [ηp2 = .25, p = .01], whereas TAU patients did not [ηp2 = .01, p = .67], with a significant difference between the conditions [ηp2 = .10, p = .03]. A sensitivity analysis with linear mixed models, however, showed weaker evidence for an additive effect of MBTp over TAU on social functioning 5 years post-treatment, F = 3.731, p = .06. MBT patients also showed a greater improvement in one aspect of mentalizing, understanding of social causality [ηp2 = 0.17, p = .04], but not other aspects of mentalizing.

The results suggest a durable effect of MBTp.