van den Robert Bosch

Psychopathology and cognition in schizophrenia spectrum disorders: the role of depressive symptoms

The cognitive correlates of five symptom dimensions based on PANSS ratings were examined in a group of 50 recent onset psychotic patients, using both objective and subjective cognitive measures. We were particularly interested in the depression dimension, since it has not been studied extensively thus far. The depression dimension showed a high number of correlations with both objective and subjective cognitive measures, such as problems with simple and divided attention, psychomotor slowing and subjectively experienced distractibility, overload and diminished attentional control. The other dimensions, including negative symptoms, have less cognitive correlates. It is possible that previous studies based on a three-dimensional model confounded correlates of negative symptoms with correlates of depressive symptoms. The results of this study suggest the need for more research into the mechanisms underlying the relationship between depressive symptoms and cognitive functioning in schizophrenia, and that patients with depressive symptoms are less efficient in information processing, but can compensate by investing more mental effort. Because subjective cognitive measures were related to mental effort in previous research, they can be a useful tool in future research.

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.