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The teenager had pink cheeks from the cold and a matter-of-fact tone as she explained why she had started using methamphetamine after becoming homeless last year. “Having nowhere to sleep, nothing to eat — that’s where meth comes into play,” said the girl, 17, who asked to be identified by her nickname, Rose. “Those things aren’t a problem if you’re using.” She stopped two months ago, she said, after smoking so much meth over a 24-hour period that she hallucinated and nearly jumped off a bridge. (Goodnough, 12/17)

Black and Hispanic Americans are especially vulnerable to Alzheimer's disease. Yet they're often underrepresented in scientific studies of the disease. So on a cool Sunday morning in Cleveland, two research associates from Case Western Reserve University's School of Medicine have set up an information table at a fundraising walk organized by the local chapter of the Alzheimer's Association. (Hamilton, 12/17)

Top athletes’ brains are not as noisy as yours and mine, according to a fascinating new study of elite competitors and how they process sound. The study finds that the brains of fit, young athletes dial down extraneous noise and attend to important sounds better than those of other young people, suggesting that playing sports may change brains in ways that alter how well people sense and respond to the world around them. (Reynolds, 12/18)

When hunter-gatherers living in what is now southern Denmark broke down pieces of birch bark into sticky, black tar about 5,700 years ago, they almost certainly didn’t realize that they were leaving future scientists their entire DNA. Ancient people used the gooey birch pitch to fix arrowheads onto arrows and to repair a variety of stone tools. When it started to solidify, they rolled the pitch in their mouths and chewed on it, like some sort of primitive bubble gum. (Sheikh, 12/17)

Every decade has its culinary trends, from gelatin molds in the ’50s to pasta salads in the ’80s. In the 2010s, the defining development was the social-media-fueled fetishization of food. It was the sheer number of Instagram-worthy food crazes and sensations. Think avocado toast, the croissant-donut hybrid known as the Cronut, and anything and everything related to kale or bacon (or possibly both—say, a paleo-friendly kale-bacon salad). (Passy, 12/17)

Wey is the founder of BabyZoos, a start-up food company focusing its work in Kalamazoo, Mich. He launched the company this year after learning a startling statistic: Black infants born in Kalamazoo County are three times as likely to die before their first birthday as white children. (Godoy, 12/17)

Increasingly, surgeons are talking about a once-taboo topic: the pain they feel after hours spent contorted into positions the human body was not meant to sustain. Surveys show that a high percentage of surgeons regularly feel musculoskeletal pain related to work and that they have twice the risk of such injuries as the general population. The pain is severe enough that some fear they will have to reduce their workloads or retire early. (Burling, 12/18)

Puppies: cute balls of fur. But according to the Centers for Disease Control and Prevention, they're also linked to a multi-state outbreak of an infection that's resistant to multiple drugs. An outbreak strain of Campylobacter jejuni has been reported in 30 states and so far 30 people have been infected, the CDC said. Four have been hospitalized but no deaths have been reported, the center said. (Maxouris, 12/18)

A cacophony of slapping noises filled the food lab at the High School for Environmental Studies in Manhattan one afternoon in late October. “Think of all the hands that have done this for thousands of years,” said Andrew Margon, an English teacher, as his students energetically pummeled lumps of corn masa into tortillas. The students were taking a cooking class as part of Food Ed., an interdisciplinary curriculum developed by the Stone Barns Center for Food and Agriculture, a nonprofit farm and educational center based near Tarrytown, N.Y., which also has a partner high-end restaurant. (Schiffman, 12/17)

While the relationship between gun violence and mental health get lots of attention, numerous studies have established a much stronger link between excessive alcohol consumption and gun violence. While politicians and media give a lot of attention to mental health in relation to gun violence, such a link has not been established in research. In fact, roughly 3 to 5% of violent crime is thought to be caused by people with a mental illness. (Dunn, 12/17)