Multiple diagnoses are the norm with mental illness; new genetic study explains why

More than half of people diagnosed with one psychiatric disorder will be diagnosed with a second or third in their lifetime. About a third have four or more. This can make treatment challenging and leave patients feeling unlucky and discouraged. But a sweeping new analysis of 11 major psychiatric disorders offers new insight into why comorbidities are the norm, rather than the exception, when it comes to mental illness.