Co-administration of atypical antipsychotics and antidepressants disturbs contrast detection in schizophrenia

Atypical antipsychotics (APDs) antagonize both serotonin and dopamine receptors. This antagonism is, however, often confounded by co-administration of other medications, such as antidepressants, that affect pharmacological activity at these receptors. While it is known that the modulation of dopamine affects cognitive processes such as working memory, the interactions between APDs and antidepressants in behaviors including sensory processes are not clear. In this study, we investigated the effect of combined treatment with antidepressants and atypical antipsychotics on memory-related visual processing in schizophrenia. We employed (1) contrast detection, a task requiring the maintenance of visual signals over a short period of time; and (2) direction discrimination, a task not requiring maintenance of visual signals. On contrast detection, the performance was significantly worse in the patients taking both APDs and antidepressants than in patients taking just APDs. On direction discrimination, however, the performance did not differ between the patients tasking just APD and those taking both APDs and antidepressants. Given that antidepressants interfere with APD's stimulation of D1 receptors via agonism of serotonin receptors, the poor performance on contrast detection suggests that the interaction between these two types of psychotropic drugs selectively disrupts the sensory processes requiring retention of visual information.