Suchergebnisse

Twin studies suggest that global and regional brain volumes are highly heritable. However, estimates of heritability vary across development. Given that all twin studies are open to the potential criticism of non-generalizability due to differences in intrauterine environment between twins and singletons, these age effects may reflect the influence of perinatal environmental factors, which are unique to twins and which may be especially evident early in life. To address this question, we compared brain volumes and the relationship of brain volumes to gestational age in 136 singletons (67 male, 69 female) and 154 twins (75 male, 79 female; 82 DZ, 72 MZ) who had received high resolution MRI scans of the brain in the first month of life. Intracranial volume, total white matter, and ventricle volumes did not differ between twins and singletons. However, cerebrospinal fluid and frontal white matter volume was greater in twins compared to singletons. While gray matter volumes at MRI did not differ between groups, the slope of the relationship between total and cortical gray matter and gestational age at the MRI scan was steeper in MZ twins compared to DZ twins. Post-hoc analyses suggested that gray matter development is delayed in MZ twins in utero and that they experience 'catch-up' growth in the first month of life. These differences should be taken into account when interpreting and designing studies in the early postnatal period.

Background: Clozapine and lithium increase neurosteroids in rodents, and both drugs demonstrate antisuicidal actions. We therefore hypothesized that neurosteroid levels may be reduced in patients with schizophrenia or bipolar disorder who completed suicide. Aims: To investigate neurosteroid levels in the parietal cortex and posterior cingulate in schizophrenia and bipolar patients who died by suicide, and compare them with patients with these disorders who died of other causes. Method: Neurosteroid levels were quantified by gas chromatography/mass spectrometry in the parietal cortex and posterior cingulate. Mann–Whitney analyses were conducted in exploratory post hoc analyses to investigate neurosteroids as possible biomarker candidates for suicide. Results: The study showed that pregnenolone was significantly decreased in the parietal cortex in the combined group of patients with schizophrenia or bipolar disorder who died by suicide (n = 13) compared with patients with these disorders who died of other causes (n = 17, p = .02). Pregnenolone levels were also lower in the parietal cortex in the individual group of schizophrenia patients who died by suicide (n = 4) compared with schizophrenia patients who died of other causes (n = 11) p = .04). Conclusion: Pregnenolone alterations may be relevant to the neurobiology of suicide in schizophrenia and bipolar disorder.