New research indicates a strong link between subthreshold manic episodes and likelihood of developing bipolar disorder in children of parents with bipolar disorder.
The study got published in the American Journal of Psychiatry and it's findings could improve clinical assessment and care for these high-risk children by potentially enabling earlier identification, treatment or possible preventive measures.
The study is among the first to show that subthreshold manic episodes — experiences that approach but do not meet the cut-offs for full-blown bipolar disorder — are important diagnostic risk factors for the development of bipolar disorder and other mental health conditions in high-risk children. In addition, it found that children of parents with bipolar disorder have substantially higher rates of subthreshold mania or hypomania (13.3 vs 1.2 percent); manic, mixed or hypomanic episodes (9.2 vs 0.8 percent); and major depressive episodes (32.0 vs 14.9 percent) than community children.
The cumulative rate of bipolar spectrum disorders at age 21 was 23 percent in the high-risk group compared to 3.2 percent in the comparison group. The mean age of onset for a bipolar spectrum disorder was 12 years, with the earliest manic episode being documented at 8 years, highlighting the importance of monitoring subthreshold symptoms for early intervention.
"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," said Dr. Axelson, who is also a professor of clinical psychiatry at The Ohio State University. "However, most children who have a parent with bipolar disorder do not develop bipolar disorder."
Among the study's high-risk children who did develop bipolar disorder, nearly all had identifiable mood episodes and other psychiatric disorders before the onset of full-fledged bipolar illness.
"Short, distinct episodes of manic symptoms were the most specific predictor of developing bipolar disorder in high-risk offspring," Dr. Axelson said. "But so far, many children with these short manic episodes have not progressed to full-fledged bipolar disorder."
This study is part of the Pittsburgh Bipolar Offspring Study (BIOS), which is the largest study to date of children of parents with bipolar disorder. Unique to BIOS is the assessment of children for subthreshold episodes of manic symptoms.
This latest publication confirms and extends the baseline findings and describes how mood episodes develop in an effort to aid in early diagnosis on the basis of those subthreshold episodes.
The longitudinal study followed high-risk children and demographically matched offspring of community parents. Follow-up interviews were completed in 91 percent of the offspring with a mean follow-up duration of 6.8 years. The initial and follow-up interviews were conducted using the Structured Clinical Interview for DSM-IV (parents) and the Schedule for Affective Disorders and Schizophrenia for School-Age Children (children). Follow-ups focused on the assessment of the interval since the previous interview.
"I am continuing to collaborate with researchers on the Pittsburgh Bipolar Offspring Study," Dr. Axelson said. "We expect to find more exciting results that will impact the diagnosis and treatment of high-risk children as we follow the participants into young adulthood."