Nobody at UN headquarters in Turtle Bay, New York, quite knows what Mr Trump’s “America First” ideas will bring, in part because there is no one to tell them.

For lifelong friends Ahan Tandon and Mihai Thompson, students at Cedar Falls High School, summer break wasn’t just about time off. It was about giving back.

Background In deprived urban areas of South America, young people face heightened risks of mental disorders. Research suggests an association exists between social media engagement (SME), depression ...