Genetic research into bipolar disorder traditionally uses strict categorical criteria to define a clinical diagnosis. However, it is common for relatives of individuals with bipolar to exhibit some evidence of mood disturbance, but not sufficient to meet the strict clinical criteria for a positive diagnosis. These individuals are correctly considered clinically unaffected, although they likely share some of the susceptibility genes underlying the disorder. Dr Fullerton has been examining the use of subclinical traits to identify individuals who share susceptibility genes in order to follow the pattern of genetic transmission of bipolar disorder through families more accurately.