Schizophrenia and bipolar disorder run in families. Up to 80 percent of cases can be traced to inheritance, but determining exactly which genetic variants among millions of possibilities that might be responsible has proved challenging.
Two studies combining thousands of patient samples – more than 10,000 people with schizophrenia and more than 7,000 people with bipolar disorder, plus larger numbers of unaffected people – have allowed differences in DNA associated with the diseases to rise above a vast sea of statistical noise.