Social media use has risen dramatically across the world over the past two decades. Yet researchers have wondered: Why does the negative impact of social media show up strongly in some countries — but not in others?The World Happiness Report, released Thursday by scholars from universities in Canada, the U.S. and China, proposes a startling answer. The fact that western countries show such consistently negative emotional impacts from social media, they conclude, is tied to the way so many young people today are using it to consume visual content passively. By contrast, countries where platforms are used primarily to enhance…