Malfunctioning（不正常工作） circadian clock（昼夜节律钟） genes may be responsible for bipolar disorder（躁郁症，两极性异常） in children. Researchers writing in the open access journal BMC Psychiatry found four versions of the regulatory gene RORB that were associated with pediatric（儿科的） bipolar disorder. Alexander Niculescu from Indiana University School of Medicine, Indianapolis, US, worked with a team of researchers at Harvard, UC San Diego, Massachusetts General Hospital and SUNY Upstate Medical University to study the RORA and RORB genes of 152 children with the condition and 140 control children. They found four alterations to the RORB gene that were positively associated with being bipolar. Niculescu said, "Our findings suggest that clock genes in general and RORB in particular may be important candidates for further investigation in the search for the molecular basis（基础，根据） of bipolar disorder".

RORB is mainly expressed in the eye, pineal gland（松果腺） and brain. Its expression is known to change as a function of circadian rhythm（生理节律） in some tissues, and mice without the gene exhibit circadian rhythm abnormalities. According to Niculescu, "Bipolar disorder is often characterized by circadian rhythm abnormalities, and this is particularly true among pediatric bipolar patients. Decreased sleep has even been noted as one of the earliest symptoms discriminating children with bipolar disorder from those with attention deficit hyperactivity disorder（注意缺陷多动障碍） (ADHD). It will be necessary to verify our association results in other independent samples, and to continue to study the relationship between RORB, other clock genes, and bipolar disorder".

Pediatric bipolar disorder is a controversial diagnosis characterized by alternating bouts（比赛，竞争） of depression and mania（狂躁症） in children, although it does not affect all young people in the same way and the duration and severity（严重） of the disorder can vary enormously.