Measuring trends is a lot easier than explaining them. The suicide epidemic among adolescents and young adults, for example, “is consistent with the broader finding on rising rates of depression and depressed mood in young people,” says psychiatrist and epidemiologist Mark Olfson of Columbia University. On the other hand, he notes, “it’s a real puzzle that suicide rates are going up at a time when substance use is going down in this age group.” The two usually go hand in hand.

A possible factor is how much time young people spend with digital devices. A 2018 study that drew on data from more than half a million teenagers, led by psychologist Jean Twenge of San Diego State University, found that screen time correlates with depressive symptoms and suicide-related behaviors (considering it, making a plan, attempting it), especially for girls. “The rise in social media, the threat of cyberbullying, of being ostracized, can be a triggering event,” Olfson says, but in terms of causality, he notes, “it’s a difficult hypothesis to evaluate.” Wang mentions other factors for which there is indirect evidence, such as parental use of opioids and exposure to a loved one’s suicide.

Among adults, suicide attempts track with the lack of a college degree, age between 21 and 34, very low income, mental illness, and a history of violence or past suicide attempts, a large study by Olfson and his colleagues found. Adults are much more likely than teenagers to actually kill themselves, in part because they have easier access to more lethal means such as guns and because they are more planful and less impulsive. Adults who take their own lives are predominantly male and white or Native American, often with a history of substance use, mental disorders, past attempts, loneliness and personal loss.