People who are depressed may become overwhelmed and exhausted and may stop participating in their routine activities. They may withdraw from family and friends. Some may even have thoughts of death or suicide. There is no single answer to this question. Some depression is caused by changes in the body's chemistry that influence mood and thought processes.
Biological factors can also cause depression.
In other cases, depression is a sign that certain mental and emotional aspects of a person's life are out of balance. For example, significant life transitions and life stresses, such as the death of a loved one, can bring about a depressive episode. Yes, it can. A person's depression is highly treatable when he or she receives competent care. It is critical for people who suspect that they or a family member may be suffering from depression seek care from a licensed mental health professional who has training and experience in helping people recover from depression.