The problem sounds so ordinary, so obvious: People in an unfamiliar location confront dislocation. On their own two legs for the first time, they’re wobbly. Who would expect otherwise?

Well, most of them did, because college isn’t sold to teenagers as just any place or passage. It’s a gaudily painted promise. The time of their lives! The disparity between myth and reality stuns many of them, and various facets of youth today — from social media to a secondary-school narrative that frames admission to college as the end of all worry — worsen the impact.

Harry Rockland-Miller, who just retired as the director for the Center for Counseling and Psychological Health at the University of Massachusetts at Amherst, told me the emblematic story of a freshman he treated:

“He was 18. He came to school and was invited to a party his first weekend, and he didn’t know anybody. So he started to drink. He drank way too much and ended up lying on a bench in his residential hall, feeling very sick. Nobody stopped and said, ‘How are you doing? Are you O.K.?’ And he felt so isolated. When he came in to speak with me the next day, the thing that struck him — what he said — was, ‘There I was, alone, with all these people around.’ ”

Alone, with all these people around. In a survey of nearly 28,000 students on 51 campuses by the American College Health Association last year, more than 60 percent said that they had “felt very lonely” in the previous 12 months. Nearly 30 percent said that they had felt that way in the previous two weeks.

Victor Schwartz, the medical director of the Jed Foundation, which is one of the nation’s leading advocacy groups for the mental health of teenagers and young adults, said that those findings were consistent with his own observation of college students today. “While they expected that academics and finances would be sources of stress,” he told me, “many students were lonely and thought this was sort of unique to them, because no one talked about it.”