Theory of mind ability predicts prognosis of outpatients with major depressive disorder

A theory of mind (ToM) deficit in patients with major depressive episodes is associated with difficulty in social adjustment, and thus may indicate a poorer prognosis. We investigated the association between ToM deficits and the outcome in patients who had recovered from major depressive episodes. We evaluated ToM abilities of 100 patients with major depressive disorder during a period of remission. The patients were followed up for one year and their outcomes observed. After one year, patients who had a ToM deficit according to a second-order false belief question relapsed significantly more frequently than did patients who did not have a deficit (Fisher's exact test P<0.0001; relative risk (RR)=8.286; CI 2.608, 26.324). Significant differences between these two groups were shown in scores of the Global Assessment of Functioning Scale (P<0.0001). Our results suggest that a ToM deficit after symptom remission in patients with major depressive disorder predicts a higher relapse rate and lower social function one year after recovering from a major depressive episode.