Predictors of improved functioning in patients with psychosis: The role of amotivation and defeatist performance beliefs

• Amotivation mediates the association of beliefs and functioning cross-sectionally.
• Change in amotivation predicts change in social functioning during therapy.
• Change in dysfunctional beliefs is unrelated to therapy outcomes.
• Amotivation is a promising treatment target to improve functioning.

Defeatist performance beliefs (DPBs) are associated with severe impairments in functioning of patients with negative symptoms of schizophrenia. This association has been found to be mediated by amotivation, a core aspect of negative symptoms. Although causality is assumed, longitudinal evidence for this is lacking. The current study aimed to extend previous findings by investigating both cross-sectional and longitudinal associations between DPBs, motivational impairments and functioning in a sample of patients with psychotic disorders (N=58). We hypothesized, that DPBs would be related to functioning in cross-sectional and longitudinal analyses and that this link would be mediated by motivational impairments. Data was assessed at baseline and post-treatment in a trial on the effects of cognitive behavior therapy for psychosis. At baseline, amotivation mediated the association between DPBs and functioning. From baseline to post-treatment, reduction of amotivation was associated with improvement of functioning significantly, whereas reduction of DPBs was unrelated to improvements in functioning or amotivation. The findings suggest that improvement in amotivation accounts for favorable treatment outcomes in regard to functioning but question the causal role of DPBs in negative symptoms and functioning.