Yet there is reason to believe that mental illness is indeed increasing around the world, if only because urbanization is increasing. By 2010, for the first time in history, more than half the world’s population lived in cities. Cities are places of possibility: They are, as E. B. White said of New York, “the visible symbol of aspiration and faith, the white plume saying that the way is up.” But cities also break traditions and fracture families, and they breed psychiatric illness. In a city you are more likely to be depressed, to fall ill with schizophrenia, and to use alcohol and drugs. Poverty and rapid urbanization sharpen these effects.

Something Dr. Thara said made me wonder about another factor: “Gadgets. All these gadgets. Nobody thinks for themselves anymore.”

We have recently learned that Facebook leads people to feel less good in the moment and less satisfied with their lives. (Some 85 million Indians use Facebook, most of them at least in part through their phones.) The authors of a University of Michigan study speculate that what drives that outcome is social comparison. Other people post flattering photographs and funny comments while your own life just feels so dull.