Family history tends to be an important predictor for mental health, but considering not all offspring of a parent with a mental illness end up developing a similar condition, early detection strategies remain instrumental to treatment and prevention. A recent study published in the American Journal of Psychiatry has found that understanding subthreshold manic episodes — a set of bipolar symptoms that does not quite meet the criteria for full-blown bipolar disorder — is essential to detecting bipolar disorder in children of parents with bipolar disorder.

"Mental health practitioners should carefully assess for short episodes of manic symptoms, major depression, and disruptive behavior disorders in high-risk children, as these are risk factors for the future onset of bipolar disorder," Dr. David Axelson, medical director of Behavioral Health at Nationwide Children's Hospital and senior author on the study, said in a statement.

Axelson and his colleagues gathered data as part of the Pittsburgh Bipolar Offspring Study (BIOS), currently the largest study to follow children of parents with bipolar disorder. Follow-up interviews, which were generally carried out for an average of 6.8 years, were conducted using the Structured Clinical Interview for DSM-IV (parents) and the Schedule for Affective Disorders and Schizophrenia for School-Age Children (children).

Researchers found that high-risk children — children of a parent with bipolar disorder — have significantly higher rates of subthreshold mania or hypomania; manic, mixed, or hypomanic episodes; and major depressive episodes. The overall rate of bipolar spectrum disorder at age 21 was 23 percent among high-risk children compared to 3.2 percent among children of a parent without bipolar disorder. The earliest manic episode was documented at 8 years, and average age of onset for a bipolar spectrum disorder was 12 years.

"This may be particularly important if medication is going to be used for treating mood or behavioral symptoms in the child, because some medications might increase the risk of developing mania or psychotic symptoms in someone who is already at very high risk for developing bipolar disorder," Axelson explained. "Prescribers might choose different medication options, or use lower doses and monitor for problems more closely."

High-risk children from the study who did develop bipolar disorder almost always showed signs of mood episodes and other psychiatric disorders before being diagnosed with a full-fledged bipolar spectrum disorder. The most specific predictors of bipolar disorder development in high-risk children were short and distinct episodes of manic symptoms.

"Most children who have a parent with bipolar disorder will have a diagnosable psychiatric disorder, such as attention-deficit disorder, oppositional defiant disorder, an anxiety disorder or depression, at some point during their youth," Axelson added. "However, most children who have a parent with bipolar disorder do not develop bipolar disorder."

According to the National Institute of Mental Health, although bipolar disorder often runs in families, most scientists agree there is no single cause. Evidence from past research has suggested people with certain genes are more susceptible to developing bipolar disorder. However, research involving one identical twin with bipolar disorder and one identical twin without bipolar disorder shows that genes are not always the case considering identical twins share the exact same genes. This has led researchers to explore factors more related to environment.

Source: Goldstein B, Goldstein T, Monk K, Yu H, Hickey MB, Axelson D, et al. Diagnostic precursors to bipolar disorder in offspring of parents with bipolar disorder: A longitudinal study. American Journal of Psychiatry. 2015.