Benjamin Rush, a physician and one of the signers of the Declaration of Independence, invented the rotational chair as a treatment for psychotic patients. He believed the chair helped improve circulation to the mentally ill brain. U.S. National Library of Medicine/Courtesy of Little Brown and Company hide caption

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Caregivers who are trained in responding to anxiety or aggression in people with dementia can effectively reduce those symptoms, studies find. iStockphoto hide caption

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Closing loopholes in background checks for gun purchases would reduce the risk of death and injury, doctors' and attorneys' groups say. Alexa Miller/Getty Images hide caption

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An Iraqi child who fled fighting between the so-called Islamic State and Kurdish peshmerga is among the some 3,000 people living at the Baharka camp, near Irbil, the capital of the Kurdish autonomous region in northern Iraq, on Jan. 16. Safin Hamed/AFP/Getty Images hide caption

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Most parents have a favorite child, psychologists say, even if they try to be fair. Hero Images Inc./Corbis hide caption

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Residents of ShantiNiketan, a retirement community near Orlando, Fla., walk in a Hindu religious procession. Courtesy of ShantiNiketan Inc. hide caption

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If 13 episodes in a row with Piper and Crazy Eyes sounds like your dream day, social scientists want to talk with you about your habits. Paul Schiraldi/NetFlix/AP hide caption

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A Kaiser mental health worker with the National Union of Healthcare Workers looks through a pile of signs Monday during day one of a week-long demonstration outside of a Kaiser Permanente hospital in San Francisco. Justin Sullivan/Getty Images hide caption

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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

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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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