When a woman became depressed, it increased the odds of depression in her close friends (male and female) by 142%. When a man became depressed, it had no measurable effect on his friends. The authors surmise that the difference is due to the fact that women are more emotionally expressive and more effective at communicating mood states within friendship pairs. When men get together, in contrast, they are more likely to do things together rather than talk about what they are feeling.
