A worker cleans the home of a hoarder in Las Vegas. Teens may not have the time to accumulate this much stuff, but they still have symptoms. AP/City of Las Vegas via Las Vegas Review-Journal hide caption

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Singer Ke$ha performs during the iHeartRadio Music Festival at the MGM Grand Garden Arena in Las Vegas in September. Ethan Miller/Getty Images hide caption

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High school students whose friends posted photos of drinking and smoking were about 20 percent more likely to become drinkers or smokers themselves. iStockphoto hide caption

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The teenage years are the last golden opportunity to build a healthy brain, researchers say. So smoking pot might not be so smart. Tomas Rodriguez/Corbis hide caption

itoggle caption Tomas Rodriguez/Corbis