Depression is associated with impairment of cognitive functions, and especially executive functions (EFs). Despite the fact that most depressed patients experience recurrence of episodes, the pattern and the severity of executive impairment have not been well characterized in this group of depressed patients. We asked if and to what extent these patients were impaired on a range of neuropsychological tests measuring EFs, and also when confounding factors were adjusted for. Forty-five patients (aged 19-51 years) with moderate to severe (Hamilton score >18) recurrent major depressive disorder (DSM-IV) were compared to 50 healthy controls matched on age, education, gender and intellectual abilities. The subjects were administered a set of neuropsychological tests that assesses sub-components of EFs. The depressed patients were impaired compared to the control group on all selected tests, with a severity of impairment within -1 standard deviation from the control group mean. The group difference was statistically significant for eight of the 10 EFs that were assessed. These were measures of verbal fluency, inhibition, working memory, set-maintenance and set-shifting. The group difference was still significant for all sub-components except for set-shifting (Wisconsin Card Sorting Test) and planning (Tower of London), when additional medication and retarded psychomotor speed was adjusted for. In conclusion, the depressed subjects were mildly impaired across a wide range of EFs. This may have a negative impact on everyday functioning for this group of patients.

A double dissociation of parietal and frontal lobe activation was found for the schizophrenia patients and the depression patients. The greater parietal lobe activation in the patients with schizophrenia may reflect a compensatory strategy for the failure to recruit cognitive processes that involve frontal lobe areas when solving a mental arithmetic task.

The aim of the study was to investigate the improvement of executive function measures upon recovery from unipolar depression. Thirty patients who suffered from recurrent major unipolar depression were retested with regard to their executive function approximately two years after an initial baseline examination. At baseline, patients were depressed (average 17-item HAM-D score 21.8), at retesting they were partially or totally recovered (average HAM-D score 8.2). There was a significant positive association between improvement on the HAM-D and improvement of executive function. In those with complete recovery, overall executive function and most examined executive function measures were no longer different from the baseline performance of healthy controls (with the possible exception of semantic fluency and Stroop Colour-word). In conclusion, recovery from major unipolar depression was accompanied by a recovery of many aspects of executive function to a normal level. Our findings support previous studies that have shown that neuropsychological impairment associated with long-standing depressive symptomatology is reversible (i. e. state-related) in recurrent unipolar depression.

Reduced performance on attention tests in major depression is because of a non-specific speed reduction and loss of vigilance consistent with lack of effort. In addition to generally impaired processing speed, the schizophrenic subjects exposed a deficit in selective attention, indicating executive dysfunction.

Schizophrenia is characterized by deficits across a wide range of NP functions. Thirty-eight percent of the patients are within normal limits. A mild and limited NP disturbance is apparent in depression.