Other psychiatric conditions. In some people, depression occurs even when life is going well. Depression is not your fault. It is not a weakness. It is a medical illness.
Depression is treatable.
People who have major depressive disorder have a number of symptoms nearly every day, all day, for at least 2 weeks. Feeling sad, blue, or down in the dumps. Feeling worthless or guilty. Increase or decrease in appetite or weight. Thoughts of death or suicide.