Cognitive dysfunctions have been well established in patients with schizophrenia (SZ). Recent studies also showed persistent cognitive impairments in patients with bipolar disorder (BD) in all phases of the disorder including the remission phase. Specific cognitive domains have been considered as candidate endophenotypes in SZ and BD. The aim of this study was to investigate the diagnostic specificity of neurocognitive deficits BD and SZ patients during a stable phase of the illness.

40 patients with schizophrenia (20 female, 30.4 ±8,1 years) were compared with 40 bipolar patients (27 female, 34.7±10.4 years) and 43 healthy volunteers (24 female, 34.7 ± 8.7 years). Executive functions (WCST), attention (CPT), immediate and delayed verbal memory (VLMT) and verbal fluency (RWT) were assessed. Differences in neurocognitive functions between diagnostic groups were analysed for each domain by analyses of covariance (ANCOVA analysis with age, education, IQ, gender and medication as covariates).

SZ and BD patients performed worse than control subjects in the WCST (p<0.001), VLMT (p<0.01) and in the CPT (p<0.03). There was no significant difference in the WCST and VLMT between SZ and BD patients. However, in the CPT, SZ patients showed a significantly greater impairment than BD patients (p<0.001). In BP patients deficits in the CPT were associated with the number of illness episodes.

The findings are comparable to previous results suggesting that the specific profile of the deficits seems to differ between the diagnosis, while the same underlying domains describe neurocognitive functioning in both groups.