Suicide rates revised for depression

Two influential research reviews, one published in 1970 and the other in 1990, concluded that about 15 percent of people diagnosed with depression will end up killing themselves.

A new study indicates that this widely cited figure considerably overstates the suicide risk among depressed people. Their actual suicide risk ranges from 2 percent to 8.6 percent, according to the study, which appears in the December American Journal of Psychiatry. Around 1 percent of the general population in the United States commits suicide.

The peak suicide risk, 8.6 percent, occurs among depressed people who have been hospitalized for threatening or trying to kill themselves, say psychiatrist John M. Bostwick and psychologist V. Shane Pankratz, both of the Mayo Clinic in Rochester, Minn. Depressed people who have received psychiatric-hospital treatment for reasons unrelated to suicide eventually kill themselves about half as commonly, Bostwick and Pankratz estimate. That figure drops to 2 percent among depressed people who get treatment outside a hospital.

“Our study shows that the most effective suicide-prevention efforts should target recent or repeatedly hospitalized [depressed] patients,” Bostwick says. No specific symptom pattern was found that foreshadows suicide among depressed patients.

The Mayo clinic researchers pooled data from the 30 studies included in the two previous reviews and 47 more-recent investigations of suicides among depressed patients. The total set of studies included more than 50,000 patients whom researchers tracked for at least 2 years after hospitalization or outpatient treatment. Most of these patients were diagnosed with depression; some were diagnosed with bipolar disorder or mood disturbances other than depression.

Bostwick and Pankratz calculated suicide risks by using the percentage of those in each treatment group who killed themselves during the studies’ follow-up periods. The two earlier reviews had focused on the percentage of suicides among only those depressed patients who had died, from any cause, during the follow-up. That approach partly explains why those analyses found a 15 percent suicide rate, the researchers hold.

Moreover, the official psychiatric definition of depression has expanded greatly since 1970 to include many people with mild to moderate symptoms. These people are less suicide prone, so their inclusion in more recent studies also helps explain the lower suicide rates, the researchers say.

Bruce Bower has written about the behavioral sciences for Science News since 1984. He writes about psychology, anthropology, archaeology and mental health issues.