The crash of the Germanwings jetliner has raised questions about mental illness and its consequences. Dr. Richard Friedman, a professor of clinical psychiatry at Weill Cornell Medical College, answered some of them.

Q: Are most people who kill themselves depressed?

A: We know from psychological autopsies that more than 90 percent of people who commit suicide have a diagnosable and potentially treatable psychiatric illness, most often depression — very often associated with alcohol or other drug abuse. Psychotic disorders like schizophrenia and schizoaffective disorder are also associated with an increased risk of suicide.

Q: Are people who commit mass murder and suicide typically depressed?

A: Mass murderers are typically young men who are loners, harbor a grudge and are very often psychotic. Those who commit murder-suicide are likely a different group of individuals. Murder-suicide is very rare, about 0.2 to 0.3/100,000 per year. Most of the perpetrators are men (40 to 50 years old), and the most common mental problem by psychological autopsy is depression.

Q: Are you concerned that coverage of this case is further stigmatizing people who suffer from depression?

A: I always worry about that. Horrifying outliers, like this case, create the false impression that psychiatric patients are dangerous, when we know the overwhelming amount of violence is perpetrated by normal people in the grip of normal human emotions. Still, there is no question that people with certain serious psychiatric illnesses are at a slightly higher risk of harming themselves and others compared with those without psychiatric illnesses, but the absolute risk is small.

Q: Does depression ever really go away?

A: Depression is often a chronic illness characterized by relapses and recurrences, but it is also very treatable. Antidepressant medication and psychotherapy are effective not just in treating acute episodes of depression, but in preventing relapses.

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