Participants were drawn from the Bipolar Disorder Research Network (BDRN), a UK-wide ongoing research programme into the genetic and non-genetic determinants of affective disorders (www.bdrn.org). Its inclusion criteria are a main lifetime diagnosis of affective disorder, age 18 years or over, UK or Irish White ethnicity (owing to the focus on genetics) and ability to give written informed consent. Individuals are excluded from the BDRN if their mood disorder is a consequence of alcohol or substance misuse, medical illness, medication or an organic brain disorder, or if they are biologically related to another participant. Participants are recruited systematically through National Health Service (NHS) mental health services (community mental health teams and lithium clinics) and non-systematically using advertisements for volunteers on the BDRN website, leaflets, posters and media coverage about the research, and also through UK-based user-led charities such as Bipolar UK and Depression Alliance. Inclusion criteria for this study were a DSM-IV best-estimate lifetime diagnosis of bipolar disorder (types 1 and 2) or recurrent major depressive disorder (unipolar depression),13 and completion of the Problem Gambling Severity Index (PGSI).2 The research had NHS ethics approval (MREC/97/7/01) and research and development approval from all participating NHS trusts and health boards.
