Familial bipolar disorder: preliminary results from the Otago Familial Bipolar Genetic Study

This paper outlines the methodologies used, and preliminary descriptive data collected, on a cohort of familial bipolar disorder (BPD) probands and first-degree relatives taking part in a descriptive and genetic study into familial BPD in New Zealand.

Fifty-five bipolar probands and 67 first-degree relatives were interviewed using the modified Diagnostic Interview for Genetic Studies (DIGS) and Family Interview for Genetic Studies (FIGS). Data was also collated from other sources. Blood samples were taken for DNA genomic analysis.

New Zealand families in which BPD segregates proved willing participants in this familial based genetic research. The methodologies used were acceptable. High rates of comorbidity were found in probands (27.3% met DSM-IV criteria for panic disorder/sub-threshold panic disorder; 12.7% for phobic disorder; 1.8% for obsessive-compulsive disorder; 9.1% for alcohol-related disorders and 7.3% for an eating disorder) and relatives (major depression 34.3%; panic disorder/sub-threshold panic disorder 12.0%; phobias 11.9% and alcohol-related disorders 11.9%). The polarity of index BPD illness was related to age of onset and frequency of comorbidity. Suicidal behaviour was common.

Psychiatric genetic research in New Zealand families is highly feasible. Emerging trends in the familial transmission of BPD include high rates of comorbidity, illness patterns based on polarity of index episode and frequent suicidal behaviour. Such trends will be delineated further as numbers accrue, perhaps enabling identification of more homogenous phenotypic subgroups than currently produced by diagnostic schemes.