First-degree relatives at risk of psychiatric disorder transmission

The transmission of psychiatric disorders to first-degree relatives is higher among those related to patients with bipolar disorders, according to data published in The Journal of Clinical Psychiatry.

Previous studies have implied the transmission of BD-I and BD-II between first-degree relatives (FDRs), but it is unclear whether the disorders show different familial aggregation patterns within each bipolar subtype and coaggregation with other psychiatric disorders.

Chih-Ming Cheng, MD, of the department of psychiatry at Taipei Veterans General Hospital in Taipei, Taiwan, and colleagues determined the major psychiatric disorders of 23,258,175 Taiwanese individuals by using a specialized dataset of mental disorders, including the psychiatric medical records between Jan. 1, 2001, and Dec 3, 2011, from the Taiwan National Health Insurance Research Database. Researchers then identified 184,958 first-degree relatives of patients with BD-I and BD-II.

Bipolar patients with the history of psychiatric hospitalization for manic episode or mixed episode were defined as BD-I subgroup. All other bipolar patients were assigned as the BD-II subgroup.

Researchers evaluated the relative risks of major psychiatric disorders by comparing patients with a 1:4 age-, sex- and kinship-matched samples without BD-I/ BD-II probands.

Data revealed that FDRs of BD-I probands had a “significantly higher” risk of BD-I than those of BD-II probands (BD-I proband: RR=15.80 vs BD-II proband: RR=5.68, P < .001). Additionally, the risk of BD-II was comparable between FDRs of BD-I and BD-II probands (BD-I proband: RR=6.48 vs BD-II proband: RR=5.89, P = .1161).

Researchers noted that while familial aggregation was greater within each BD subtype than among cross-subtypes, the FDRs of BD-I probands had an increased risk of schizophrenia (BD-I probands: RR=5.83 vs BD-II probands: RR=2.72, P < .001), and the FDRs of BD-II probands had a higher risk of attention-deficit/ hyperactivity disorder (BD-II probands: 2.36 vs BD-I probands: 1.93, P = .0009).

“The present comprehensive findings may facilitate genetic counseling in clinical practice and the development of distinct preventive interventions during the early stages of psychiatric disorders among the FDRs of BD-I and BD-II probands,” Cheng and colleagues wrote. “Further cross-disorder [genome-wide association studies] are required to complement the limited data on the unique and shared genetic bases between the different bipolar disorder subtypes and other major psychiatric disorders.”