So George and Tirril had discovered that two things make depression much more likely—having a severe negative event, and having long-term sources of stress and insecurity in your life. But the most startling result was what happened when these factors were added together. Your chances of becoming depressed didn’t just combine: they exploded. For example—if you didn’t have any friends, and you didn’t have a supportive partner, your chances of developing depression when a severe negative life event came along were 75 percent.11 It was much more likely than not.
