And your so right,
The causes of depression aren't fully understood. A number of factors may make a person more likely to experience depression, such as family tendency, side effects of certain medications, an introverted personality,and emotionally upsetting event, particularly those involving a loss.
Depression may also arise or worsen without any apparent or significant life stress.
Women are twice as likely as men to experience depression, though the reasons aren't entirely clear. Psychologic studies show that women tend to respond to adversity by withdrawing into themselves and blaming themselves. In contrast men tend to deny adversity and throw themselves into activities. Of biologic factors, hormones are the ones involved. Changes in hormone levels, which can create mood changes shortly before menstruation and after childbirth might play a role in women.Similar hormonal changes may occur with the use of oral contraceptives in women who have experienced depression.
Abnormal thyroid function, which is faily common in women, may also be a factor
Depression that follows a traumatic event such as the death of a loved one, is called Situational depression
Depression without an apparent precipitation event is called Endogenous depression. Depression may also occur with or be caused by a number of physical diseases or disorders.
Various prescription drugs, most notably drugs used to treat high blood pressure, can cause depression For unknown reasons, corticosteroids often cause depression when they are produced in large amounts as part of a disease, as in Cushing.s syndrome, but tend to cause elation when they are given as medication
A number of psychiatric conditions can predispose a person to depression, including certain anxiety disorders,Alcoholism, and other substance abuse disorders, schizophrenia, and the early phase of dementia.

Rosie L