But if treatment is so helpful, why hasn’t its expansion halted or reversed suicide trends?

“This is the question I’ve been wrestling with: Are we somehow causing increased morbidity and mortality with our interventions?” said Dr. Thomas Insel, former director of the National Institute of Mental Health and now president of Mindstrong Health, which makes technology to monitor people with mental health problems.

“I don’t think so,” Dr. Insel continued. “I think the increase in demand for the services is so huge that the expansion of treatment thus far is simply insufficient to make a dent in what is a huge social change.”

Drug trials and other randomized studies are virtually useless for capturing measurable effects on suicide. Most drug trials explicitly exclude subjects deemed a suicide risk; even when they don’t, the studies don’t last long enough to say anything definitive about who commits suicide.

But one recent study, by Danish researchers, supported the benefits of therapeutic intervention.

Using detailed medical records, the investigators studied more than 5,500 people who had been treated for deliberate self-harm, including cutting and clear suicide attempts.

Over decades, the portion of those people who got psychotherapy at suicide clinics were about 30 percent less likely to die or commit further self-harm than those who did not.

“I personally think that it’s the quality of care that matters, not the quantity,” Dr. Insel said. “We need more access, better measures and better quality of care.”

But in this country, many of those who commit suicide have received little or no professional help. Indeed, they rarely tell anyone beforehand of their plan — when there is one. Often the act is impulsive.