Bipolar affective disorder (BPAD), also known as manic-depressive illness, is a common complex polygenic disorder characterized by cyclical episodes of mania and depression. A genetic predisposition/susceptibility to BPAD has been strongly suggested by family, twin, and adoption studies, but no genes have yet been identified. A large Turkish pedigree with an apparent autosomal dominant BPAD and 13 affected people has been observed. The onset age ranged from 15 to 40 years, with a mean of 25 years. The phenotypes included reoccurring manic and major depressive episodes, as well as suicidal ideation; lithium treatment usually resulted in full remission. A genome-wide linkage analysis using a dominant mode of inheritance revealed a BPAD susceptibility locus on a chromosome. A person must have had a minimum of one episode of mania or hypomania to get diagnosed with bipolar disorder. Hypomania is a milder form of mania without psychotic episodes. People suffering from hypomania can frequently function well in social situations and at work.
