Sadness and social isolation can be clues to depression. Although everyone has sad feelings at times, prolonged sadness can be dangerous. Withdrawing from formerly pleasurable activities, refusing to talk with friends or family, or choosing to be alone most of the time can be signs of depression. Marked changes in attitude and personal appearance sometimes precede suicide attempts. Changes in eating or sleeping patterns also are common.
Mood swings can be a sign of depression.
Also, it is important to be aware that if someone suddenly becomes very calm after a period of deep gloom or moodiness, he or she may have decided on a suicide plan. The calm stems from having made the decision. Sudden participation in dangerous activities, such as high-speed driving or unsafe sex, can be clues to suicidal thinking. Reckless use of alcohol and drugs often goes hand in hand with suicide. Struggles caused by life crises.