A University of Missouri study shows that if your Facebook lurking triggers envy, then depression may follow. Adam Hester/Blend Images/Corbis hide caption

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Sgt. Mark Miranda, a public affairs specialist at Joint Base Lewis-McChord in Washington state, demonstrates the use of a program in July 2011 that was designed to help calm symptoms of post-traumatic stress and traumatic brain injury. A new class of apps is offering more sophisticated mental health help to struggling teens, including emergency, 24/7 connection to counselors. Ted S. Warren/AP hide caption

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One of the scariest parts of advanced macular degeneration can be losing the ability to read facial expressions. Maria Pavlova /iStockphoto hide caption

itoggle caption Maria Pavlova /iStockphoto

Teenagers' sleep patterns may be a clue to their risk of depression. iStockphoto hide caption

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Girls are particularly vulnerable to brain changes caused by stress or trauma, researchers say. Allen Johnson/iStockphoto.com hide caption

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Older men may have guns in the home that can pose a risk when people are depressed or not thinking clearly. iStockphoto.com hide caption

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