Circadian clock gene linked to bipolar disorder in children

A gene implicated in regulating how much sleep a child needs has been linked to bipolar disorder. Variations in a gene called RORB, which is known to affect sleeping patterns through disrupting the regulation of the body's internal 'circadian rhythm', are likely more common among children with bipolar disorder, according to research published online in the journal BMC Psychiatry. But more research is needed to validate the findings, said the researchers.

Previous studies have identified sleep problems as characteristic of bipolar disorder in children. 'Decreased sleep has been noted as one of the earliest symptoms discriminating children with bipolar disorder from those with attention deficit hyperactivity disorder (ADHD). For these reasons, circadian rhythm abnormalities in general, and circadian clock genes in particular, have been proposed as possible mechanistic underpinnings for bipolar disorder,' the authors wrote in their paper.

Bipolar disorder, previously known as manic depression, is a condition characterised by strong mood swings, alternating between phases of depression and mania. It affects around one in every hundred people. Men and women are affected equally but it is less common among children as it normally appears in later life. The disorder tends to run in families, suggesting that genetic factors play a part, although normally it is a stressful or traumatic event which initially triggers the condition.

The scientists identified four variations in the RORB gene as being associated with bipolar polar among the 152 children tested with the condition. This was compared to a control group of 140 children with ADHD or no mental health condition. They carried out an additional study to test the RORB gene of a an independent group, comprised of 153 children with bipolar disorder and their parents, however, none of the same gene variations were found to accurately predict the condition within this group.

Given these discrepancies, the researchers stressed that the results are not conclusive, partly due to the small sample size of the children included in the study. They have called for further investigations into the potential link between the RORB gene and bipolar disorder. Alexander Niculescu, who led the study with colleagues from Indiana University School of Medicine, believes that other genes associated with the circadian clock may also provide clues to the development of bipolar disorder in children. 'Clock genes in general and RORB in particular may be important candidates for further investigation in the search for the molecular basis of bipolar disorder,' he said. '[But] it will be necessary to verify our association results in other independent samples to continue to study the relationship between RORB, other clock genes, and bipolar disorder.'

The study was a collaboration between researchers at the Indiana University School of Medicine and Harvard, UC San Diego, Massachusetts General Hospital and SUNY Upstate Medical University.