David Adam is a writer and editor at the journal Nature and was a special correspondent at the Guardian, writing about science, medicine and the environment. Courtesy of Farrar, Straus and Giroux, LLC hide caption

itoggle caption Courtesy of Farrar, Straus and Giroux, LLC

U.S. soldiers at Long Binh base in South Vietnam line up to give urine samples at a heroin detection center before departing for the United States. About 20 percent of soldiers said they were addicts, but most didn't continue drug use back home. AP hide caption

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Relatives of victims of gun violence attend a press conference honoring the second anniversary of the Sandy Hook Elementary School shootings in Washington, D.C. on Dec. 10, 2014. Saul Loeb/AFP/Getty Images hide caption

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They're not just surfing for fun. Youngsters in Cape Town's Waves for Change are facing mental health problems. With the help of a surfing mentor and a counselor, they can learn how to cope. Anders Kelto/NPR hide caption

itoggle caption Anders Kelto/NPR

Meghan, 23, began experiencing hallucinations at 19. "Driving home, cars' headlights turned into eyes. The grills on the cars turned into mouths and none of them looked happy. It would scare the crap out of me," Meghan says. Marvi Lacar for NPR hide caption

itoggle caption Marvi Lacar for NPR

In this image taken from video on Jan. 15, police officers Edward Sarama (from left) and Robert McGuire try to talk to officer Matt Dougherty, who is pretending to be mentally ill, during a training simulation at Montgomery County Emergency Service in Norristown, Pa. Michael Rubinkam/AP hide caption

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Leon Evans, director of the community mental health system for Bexar County and San Antonio, broke through barriers that had hindered care. Jenny Gold/Kaiser Health News hide caption

itoggle caption Jenny Gold/Kaiser Health News