Worse, antidepressants, which can be lifesaving, are probably being underused in young people. Their use fell significantly after the Food and Drug Administration issued its so-called black-box warning in 2004, stating that all antidepressants were associated with a risk of increased suicidal feeling, thinking and behavior in adolescents. That warning was later extended to young adults.

One very large study, including 1.1 million adolescents and 1.4 million young adults, examined data for automated health care claims for 2000 to 2010 from 11 health plans in the United States Mental Health Research Network. Disturbingly, the study found that antidepressant use plunged 31 percent among adolescents and 24 percent among young adults within two years after the F.D.A. advisory was issued.

It’s not hard to understand why. The F.D.A.’s well-intended warning was alarming to the public and most likely discouraged many patients from taking antidepressants. Physicians, too, were anxious about the admittedly small possible risks posed by antidepressants and were probably more reluctant to prescribe them.

What the public and some in the medical community did not understand then — and perhaps still don’t know — is that the risk of antidepressant treatment is minuscule: In the F.D.A. meta-analysis of some 372 clinical trials involving nearly 100,000 subjects, the rate of suicidal thinking and behavior was 4 percent in people taking antidepressants, compared with 2 percent in people taking a placebo.

This very small risk of suicidal behavior posed by antidepressant treatment has always been dwarfed by the deadly risk of untreated depression: 2 to 15 percent of depressed people actually commit suicide.

The somewhat good news is that the downward trend in antidepressant use among adolescents following the F.D.A. advisory reversed a bit after 2008. Still, the rates of antidepressant use since the F.D.A. warning was issued have remained below the levels that would have been predicted based on pre-warning use patterns.

This pattern is very disturbing, since in the decade before this downturn in prescribing of antidepressants — 1990 to 2000 — there was a steady decline in adolescent suicide rates that coincided with an increase in the use of antidepressants in this age group.

One study found that a 1 percent increase in adolescent use of antidepressants was associated with a decrease of 0.23 suicides per 100,000 adolescents per year. (Of course, correlation cannot prove causality; other factors, like reduced rates of alcohol and drug use and more stringent gun safety regulations during this period, may have played a role, too.)