Environmental Theory of Depression

Environmental factors, however, may also play a role in depression. When combined with a biochemical or genetic predisposition, life stressors (such as relationship problems, financial difficulties, death of a loved one, or medical illness) may cause the disease to manifest itself.
John (not his real name), 25, was diagnosed with depression for the first time last year when he and his girlfriend ended their three-year relationship. "I couldn't do anything because I was totally absorbed with the whole break-up issue," he says. "It was impossible for me to sleep, and I would wake up at 3 or 4 in the morning and literally shake. And when it was time to wake up, I just couldn't get out of bed."

In addition, substance abuse and side effects from prescription medication may also lead to a depressive episode. And research shows that people battling serious medical conditions are especially prone to depression. According to the U.S. Department of Health and Human Services, those who have had a heart attack, for example, have a 40 percent chance of being depressed.

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