If you or someone you know has experienced five or more symptoms listed below for a period of two weeks or more, a thorough evaluation by a qualified mental health professional is recommended.
Symptoms of Major Depression

• Sadness, anxiety, or "empty" feelings
• Decreased energy, fatigue, being "slowed down"
• Loss of interest or pleasure in activities that were once enjoyed, including sex
• Insomnia, oversleeping, or waking much earlier than usual
• Loss of weight or appetite, or overeating and weight gain
• Feelings of hopelessness and pessimism
• Feelings of helplessness, guilt, and worthlessness
• Thoughts of death or suicide, or suicide attempts
• Difficulty concentrating, making decisions, or remembering
• Restlessness, irritability or excessive crying
• Chronic aches and pains or physical problems that do not respond to treatment

source: National Institute of Health Publication No. 97-4266 and 99-3561

What is shown above are the symptoms of clinical depression. The symptoms are not necessarily caused by external events, but external events can definitely trigger depression.

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