Scientists say they've identified a flawed gene that appears to promote manic-depression, or bipolar disorder, a finding that could eventually help guide scientists to new treatments.
A particular variant of the gene was associated with only about 3 percent of cases in a study, but researchers said other variants might be involved with more.
Follow-up research might help reveal the mysterious underlying biology that makes some people susceptible to the disorder, and so help scientists devise new treatments, said the study's senior author, Dr. John Kelsoe of the University of California, San Diego.
The work is reported in Monday's issue of the journal Molecular Psychiatry.
Previous studies have suggested that other genes are involved in manic-depression. But one expert, Dr. Melvin McInnis of Johns Hopkins University in Baltimore, said in an interview that he thinks Kelsoe's new work and another recent study provide the strongest evidence for involvement of particular genes in the disease.
Manic-depression, which affects about 2.3 million American adults, involves episodes of depression and mania, states of abnormally high mood or irritability.
While effective treatment is available, scientists would like to find better medications.
Genetics clearly play a role. Kelsoe's work focused on a gene called GRK3, which influences the brain's sensitivity to chemical messages brain cells send each other. Defects in the gene might promote manic-depression by making people oversensitive to these messages, which are carried by dopamine and other substances, he said.
Kelsoe and colleagues found statistical evidence tying a particular variant of the GRK3 gene to the disease. They tracked the inheritance of this variant from parent to child in families with a history of bipolar disorder. Overall, the variant was passed along more often than one would expect by chance to a child who later developed the disease.
That suggests the variant promotes susceptibility to bipolar disorder.
The association between the variant gene and the disorder appeared in one group of 153 families and a second group of 275 families. That association is only statistical, and Kelsoe said researchers now are looking for biological evidence that this variant of the gene acts abnormally.
1. 所谓"躁郁症"（manic-depression），一般而言是指个体有时出现抑郁的症状，有时又出现狂躁的症状，此两种特征不断的交互出现之情形，因此又称之为双极性疾患（bipolar disorder），也就是说个体会出现两极的情绪反应，一为狂躁，另一为抑郁。当个体在狂躁阶段，其出现的特征为情绪异常兴奋、自我膨胀，睡眠时数减少，非常健谈、多话，常常是滔滔不绝讲个没完，另外他们的思考或想法也经常跳来跳去，称之为跳跃性思考（flight of ideas），易分心，在行为上我们可以看到其常常疯狂购物，而不管价钱多少等失控行为特征。当个体处于抑郁的阶段，其特征又显示出心情沮丧低沈、对任何事缺乏反应或兴趣、体重改变、产生睡眠困扰、缺乏活力、负向的认知或看法等等的特征。