Causal mechanisms of subjective cognitive dysfunction in schizophrenic and depressed patients.

We examined causal mechanisms of subjective cognitive (dis)abilities in schizophrenic and depressed patients, and in patient and normal control groups. This exploratory study included objective cognitive performance (Continuous Performance Task) as well as mood and mental effort ratings. Self-report of cognitive dysfunction in patients was not correlated with objective cognitive deficits. Correlational patterns differed between groups. Our findings in schizophrenic and depressed patients point to different causal mechanisms of their subjective cognitive malaise, despite similar subjective ratings. Depressed patients associate high mental effort during task performance with a reduced cognitive efficacy, whereas schizophrenic patients associate high effort with cognitive symptoms like distractibility and overload.