What disease in the world today disables the most people? By many measures, it’s depression — and that holds nearly everywhere, whether you live in Zimbabwe or the United States. In poor countries, virtually no one gets treatment. But even rich countries run short. A survey in 2013 and 2014 found that about half a million residents of New York City had depression and that fewer than 40 percent of them got treatment.

The city is taking this problem seriously, mainly through the efforts of ThriveNYC, a program founded by Mayor Bill de Blasio’s wife, Chirlane McCray. (It has had mixed success — more on this later.) Perhaps the most curious effort involves giant orange Lego-style blocks on the sidewalk outside agencies called Neighborhood Health Action Centers in the Tremont section of the Bronx, East Harlem, and Brownsville in Brooklyn. These Friendship Benches show up at gatherings like street fairs as well.

The program involves people like Helen Skipper, known as Skip, and Steven Lopez. They sit on the benches and people talk to them about their problems. Ms. Skipper and Mr. Lopez aren’t therapists. Their most important credential is something you can’t teach — they’ve been there. “These are nontraditional safe spaces in plain view — no strings attached,” said Takeesha White, who is the acting assistant commissioner for the Bureau of Systems Partnership in the Center for Health Equity, which is part of the city’s health department. “You can work with someone who has a heart and understands and has been through the system.”

Mr. Lopez, 52, is a licensed counselor; his expertise is substance abuse treatment. Before that, it was substance abuse. His own route to sobriety started in 2009, when his wife was about to give birth to their first child and told him to choose. Then someone approached him on the street and offered him $20 to answer some questions for 10 minutes. Those questions turned out to be about what he wanted to do with his life. “I would love to be a drug counselor,” he told her. “If anything, I already have a master’s degree in drugs.”