A study came out last week that should have caused great alarm. For 13 years, researchers at the University of Copenhagen studied more than a million women between the ages of 15 and 34 who were taking a type of drug — one that is popular in all developed countries. Taking this drug, the researchers found, correlated with an increase in the risk of depression. The correlation was particularly strong in adolescent girls, who showed an 80 per cent higher chance of being diagnosed with depression.