But the real story of 20th-century psychiatry is how complex mental illness is and how difficult it is to treat.

Until that time, treatments that actually targeted these complex illnesses were practically non-existent.

One thing is certain - depression is a complex illness with many contributing factors.

AIDS is a syndrome, rather than a single disease, because it is a complex illness with a wide range of complications and symptoms.

"The physicians whose training was in primary care are dealing with very complex illnesses and conditions that should be treated by subspecialists," she said.

But now, he said, there is a growing realization that "chronic pain is itself an illness, and it's a complex illness."

Depression is a complex illness that can easily leave you feeling overwhelmed.

Contributing factors are an aging boomer population, increasingly complex illnesses and evidence-based medical practice that requires information-technology skills.

Here's an easy-to-use guide to a complex illness: Parkinson's disease.

An addiction is a complex illness with physical and psychological symptoms, affecting not only the patient, but their family, friends and social environment too.