In recent months, Silicon Valley executives have been speaking out about the purposely addictive designs of smartphones and social media, which make them hard to put down for anyone, but particularly teenagers. Now, a new report puts numbers to the warnings:, tying a sudden and large drop in adolescents’ happiness with the proliferation of smartphones, and finding that the more hours a day teens spend in front of screens, the less satisfied they are. The report, “Decreases in Psychological Well-Being Among American Adolescents After 2012 and Links to Screen Time During the Rise of Smartphone Technology, “was published Monday in the journal Emotion using a large national survey of 8th, 10th, and 12th graders conducted annually by The University of Michigan.