Bipolar disorder (BD) affects young people in their teens or early 20s and follows a lifelong recurrent course. The risk of bipolar disorder is influenced significantly by genetic factors; identification of the risk genes will be important for early and accurate diagnosis as well as for optimal treatment. In many, but not all patients the episodes of mania and depression can be prevented by suitable long term medication treatment. To date, long term treatments are commonly chosen by trial-and-error, often taking months or even years. However, our earlier work suggests that clinical and molecular genetic markers can guide the long-term treatment selection on individual basis. We propose to develop clinically applicable tools based on analysis of genetic and clinical information that will: 1) lead to an early and accurate diagnosis; and 2) more precise selection of an effective long term treatment. Early detection will facilitate timely treatment and will help identifying people at substantial genetic risk who could benefit from preventive interventions. Personalized treatment selection will shorten time to remission and effective mood stabilization. Together, our work will provide the substrate for large-scale, long term studies that will inform the treatment guidelines and transform clinical care for persons with BD by providing the tools for early detection, selection of optimal treatment, and ultimately reducing the impact of the illness on lives of patients and their families.