"Night owls are more depressed than morning people, study suggests." It is justified. It does not make a cause-and-effect statement. The headline is not justified. A better headline is "Depression causes insomnia." The headline is not justified. A better headline is "Staying up late causes depression." The headline is not justified. A better headline is "Waking up early reduces depression." The headline is not justified. A better headline is "Morning people are happier than night owls, study suggests."