ABSTRACT
BACKGROUND: Impaired mentalizing ability - an impaired ability to understand one's own and other people's behavior in terms of mental states - is associated with social dysfunction in non-affective psychotic disorder (NAPD). We tested whether adding mentalization-based treatment for psychotic disorder (MBTp) to treatment as usual (TAU) results in greater improvement in social functioning. METHODS: Multicenter, rater-blinded, randomized controlled trial. Eighty-four patients with NAPD were assigned to TAU or MBTp plus TAU. Patients in the MBTp group received 18 months of MBTp, consisting of weekly group sessions and one individual session per 2 weeks. Social functioning was measured using the Social Functioning Scale. We conducted ANCOVAs to examine the difference between treatment conditions directly after treatment and at 6-month follow-up and performed moderation and mediation analyses. RESULTS: Intention-to-treat analyses showed no significant differences between groups post-treatment (p = 0.31) but revealed the MBTp group to be superior to TAU at follow-up (p = 0.03). Patients in the MBTp group also seemed to perform better on measures of mentalizing ability, although evidence of a mediation effect was limited (p = 0.06). Lastly, MBTp treatment was less effective in chronic patients than in recent-onset patients (p = 0.049) and overall symptoms at baseline were mild, which may have reduced the overall effectiveness of the intervention. CONCLUSION: The results suggest that MBTp plus TAU may lead to more robust improvements in social functioning compared to TAU, especially for patients with a recent onset of psychosis.