Recent years have seen considerable progress in epidemiological and molecular genetic research into environmental and genetic factors in schizophrenia, but methodological uncertainties remain with regard to validating environmental exposures, and the population risk conferred by individual molecular genetic variants is small. There are now also a limited number of studies that have investigated molecular genetic candidate gene-environment interactions (G × E), however, so far, thorough replication of findings is rare and G × E research still faces several conceptual and methodological challenges. In this article, we aim to review these recent developments and illustrate how integrated, large-scale investigations may overcome contemporary challenges in G × E research, drawing on the example of a large, international, multi-center study into the identification and translational application of G × E in schizophrenia. While such investigations are now well underway, new challenges emerge for G × E research from late-breaking evidence that genetic variation and environmental exposures are, to a significant degree, shared across a range of psychiatric disorders, with potential overlap in phenotype.
This meta-analysis suggests that there is no association between this BDNF polymorphism and hippocampal volumes. For each BDNF genotype, the hippocampal volumes were significantly lower in neuropsychiatric patients than in healthy controls.
We conducted a systematic review to assess the evidence for specific effects of cannabis on impulsivity, disinhibition and motor
control. The review had a specific focus on neuroimaging findings associated with acute and chronic use of the drug and covers literature
published up until May 2012. Seventeen studies were identified, of which 13 met the inclusion criteria; three studies investigated
acute effects of cannabis (1 fMRI, 2 PET), while six studies investigated non-acute functional effects (4 fMRI, 2 PET), and four studies
investigated structural alterations. Functional imaging studies of impulsivity studies suggest that prefrontal blood flow is lower in chronic
cannabis users than in controls. Studies of acute administration of THC or marijuana report increased brain metabolism in several brain
regions during impulsivity tasks. Structural imaging studies of cannabis users found differences in reduced prefrontal volumes and white
matter integrity that might mediate the abnormal impulsivity and mood observed in marijuana users. To address the question whether impulsivity
as a trait precedes cannabis consumption or whether cannabis aggravates impulsivity and discontinuation of usage more longitudinal
study designs are warranted.
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