WEDNESDAY, Nov. 8, 2017 (HealthDay News) -- In a finding that pulls the roots of two mental illnesses closer together, researchers say people with bipolar disorder that's resistant to the drug lithium have a high number of genes associated with schizophrenia.
Since the 1950s, lithium has been widely used to treat bipolar disorder. The drug stabilizes mood swings -- the highs and lows associated with the disorder -- and reduces the risk of suicide. But nearly one-fourth of patients don't respond to the drug and about 30 percent have only a partial response.
To learn more about why some don't respond to the treatment, researchers studied the genetics of more than 2,500 bipolar patients who were given lithium.
"We found that patients clinically diagnosed with bipolar disorder who showed a poor response to lithium treatment all shared something in common: a high number of genes previously identified for schizophrenia," said study author Bernhard Baune, head of psychiatry at the University of Adelaide, in Australia.
"This doesn't mean that the patient also had schizophrenia -- but if a bipolar patient has a high 'gene load' of schizophrenia risk genes, our research shows they are less likely to respond to mood stabilizers such as lithium," he said in a university news release.
"In addition, we identified new genes within the immune system that may play an important biological role in the underlying pathways of lithium and its effect on treatment response," Baune said.
The study was published Nov. 8 in the journal JAMA Psychiatry.
"In conjunction with other biomarkers and clinical variables, our findings will help to advance the highly needed ability to predict the response to treatment prior to an intervention, Baune said.
"This research also provides new clues as to how patients with bipolar disorder and other psychiatric disorders should be treated in the future," he added.
The U.S. National Institute of Mental Health has more on bipolar disorder.