Depression

1. The biological causes of depression are physical changes in the brain, which can be caused by problems with the neurotransmitters and neurons. Also changes in the body's balance of hormones, which can be a result of problems in the thyroid, menopause, or other condition. Inherited traits are also involved in causes of depression.

2. The environmental causes of depression are life events such as the death or loss of familiars of loved ones, financial problems, and high stress. Early childhood traumas can be also a cause of depression, traumatic events during childhood such as abuse or loss of a loved one which can cause permanent changes in the brain.

3. Cognitive causes of depression are learned through relationships, unfavorable life situations often in childhood and the formative years. People view the world in a negative way, this negative view is usually a distortion of reality.

4. The Cognitive Triad is based in 3 beliefs that can cause depression and affect each other. These things are negative views of the self, the world, and to the future. As an example if a soccer player fails a penalty will believe he is a failure, then will believe everyone is against him, and finally he will believe he will fail in a future and would never be good at something.

http://www.thestudentroom.co.uk/showthread.php?t=564306
http://www.md-phc.com/puntil/ccausesof.htm
http://www.personalityresearch.org/papers/allen.html
http://www.allaboutdepression.com/cau_04.html