Multiple sources of information are essential for accurate estimation of lifetime prevalences of psychotic disorders. The use of comprehensive methods reveals that their lifetime prevalence exceeds 3%.

Objective An association between bipolar disorder and cognitive impairment has repeatedly been described, even for euthymic patients. Findings are inconsistent both across primary studies and previous meta‐analyses. This study reanalysed 31 primary data sets as a single large sample (N = 2876) to provide a more definitive view. Method Individual patient and control data were obtained from original authors for 11 measures from four common neuropsychological tests: California or Rey Verbal Learning Task (VLT), Trail Making Test (TMT), Digit Span and/or Wisconsin Card Sorting Task. Results Impairments were found for all 11 test‐measures in the bipolar group after controlling for age, IQ and gender (Ps ≤ 0.001, E.S. = 0.26–0.63). Residual mood symptoms confound this result but cannot account for the effect sizes found. Impairments also seem unrelated to drug treatment. Some test‐measures were weakly correlated with illness severity measures suggesting that some impairments may track illness progression. Conclusion This reanalysis supports VLT, Digit Span and TMT as robust measures of cognitive impairments in bipolar disorder patients. The heterogeneity of some test results explains previous differences in meta‐analyses. Better controlling for confounds suggests deficits may be smaller than previously reported but should be tracked longitudinally across illness progression and treatment.

The effects of gut microbiota on the central nervous system, along its possible role in mental disorders, have received increasing attention. Here we investigated differences in fecal microbiota between 28 patients with first-episode psychosis (FEP) and 16 healthy matched controls and explored whether such differences were associated with response after up to 12months of treatment. Numbers of Lactobacillus group bacteria were elevated in FEP-patients and significantly correlated with severity along different symptom domains. A subgroup of FEP patients with the strongest microbiota differences also showed poorer response after up to 12months of treatment. The present findings support the involvement of microbiota alterations in psychotic illness and may provide the basis for exploring the benefit of their modulation on treatment response and remission.

Disturbed circadian rhythms have been observed in seasonal affective disorder (SAD). The aim of this study was to further investigate this connection, and to test for potential association between polymorphisms in circadian clock-related genes and SAD, seasonality (seasonal variations in mood and behavior), or diurnal preference (morningness-eveningness tendencies). A total of 159 European SAD patients and 159 matched controls were included in the genetic analysis, and subsets were screened for seasonality (n ¼ 177) and diurnal preference (n ¼ 92). We found that diurnal preference was associated with both SAD and seasonality, supporting the hypothesis of a link between circadian rhythms and seasonal depression. The complete case-control material was genotyped for polymorphisms in the CLOCK, Period2, Period3, and NPAS2 genes. A significant difference between patients and controls was found for NPAS2 471 Leu/Ser (w 2 ¼ 9.90, Bonferroni corrected P ¼ 0.035), indicating a recessive effect of the leucine allele on disease susceptibility (w 2 ¼ 6.61, Bonferroni corrected P ¼ 0.050). Period3 647 Val/Gly was associated with self-reported morningness-eveningness scores (n ¼ 92, oneway ANOVA: F ¼ 4.99, Bonferroni corrected P ¼ 0.044), with higher scores found in individuals with at least one glycine allele (t ¼ 3.1, Bonferroni corrected P ¼ 0.013). A second, population-based sample of individuals selected for high (n ¼ 127) or low (n ¼ 98) degrees of seasonality, was also genotyped for NPAS2 471 Leu/Ser. There was no significant difference between these seasonality extreme groups, and none of the polymorphisms studied were associated with seasonality in the SAD case-control material (n ¼ 177). In conclusion, our results suggest involvement of circadian clock-related polymorphisms both in susceptibility to SAD and diurnal preference.

These results indicate that premorbid visuospatial reasoning is impaired in bipolar disorder and schizophrenia and, to a smaller extent, in other psychoses. This suggests that a subtle neurodevelopmental aberration is involved in the etiology of bipolar disorder and schizophrenia. High arithmetic test performance may be associated with greater risk for bipolar disorder.

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The high heritability of bipolar disorder was demonstrated in a nationwide population-based twin sample assessed with structured personal interviews.

The high heritability of bipolar disorder was demonstrated in a nationwide population-based twin sample assessed with structured personal interviews.