Molecular genetics of bipolar disorder.

Background A robust body of evidence from family, twin and adoption studies demonstrates the importance of genes in the pathogenesis of bipolar disorder. Recent advances in molecular genetics have made it possible to identify these susceptibility genes. Aims To present an overview for clinical psychiatrists. Method Review of current molecular genetics approaches and emerging findings. Results Occasional families may exist in which a single gene plays a major role in determining susceptibility, but the majority of bipolar disorder involves more complex genetic mechanisms such as the interaction of multiple genes and environmental factors. Molecular genetic positional and candidate gene approaches are being used for the genetic dissection of bipolar disorder. No gene has yet been identified but promising findings are emerging. Regions of interest include chromosomes 4p16, 12q23-q24, 16p13, 21q22, and Xq24-q26. Candidate gene association studies are in progress but no robust positive findings have yet emerged. Conclusion It is almost certain that over the next few years the identification of bipolar susceptiblity genes will have a major impact on our understanding of disease pathophysiology. This is likely to lead to major improvements and treatment in patient care, but will also raise important ethical issues.