When doctors talk about depression, they mean the medical illness called major depression. Someone with major depression has most or all of the symptoms listed in the box below nearly every day, all day, for 2 weeks or longer.
Minor depression has the same causes and treatment as major depression.
Your brain has chemicals that help control your moods. When you don't have enough of these chemicals or your brain doesn't respond to them properly, you may become depressed. Depression also can be linked to events in your life, such as the death of a loved one, a divorce or losing a job. Taking certain medicines, abusing drugs or alcohol, or having other illnesses can also lead to depression. Depression isn't caused by personal weakness.