Depression

1. Explain the biological causes of depression.
Additional research data indicate that people suffering from depression have imbalances of neurotransmitters, natural substances that allow brain cells to communicate with one another. Two transmitters implicated in depression are serotonin and norepinephrine. Scientists think a deficiency in serotonin may cause the sleep problems, irritability, and anxiety associated with depression. Likewise, a decreased amount of norepinephrine, which regulates alertness and arousal, may contribute to the fatigue and depressed mood of the illness.
Other body chemicals also may be altered in depressed people. Among them is cortisol, a hormone that the body produces in response to stress, anger, or fear. In normal people the level of cortisol in the bloodstream peaks in the morning, then decreases as the day progresses. In depressed people, however, cortisol peaks earlier in the morning and does not level off or decrease in the afternoon or evening.
Researchers don't know if these imbalances cause the disease or if the illness gives rise to the imbalances. They do know that cortisol levels will increase in anyone who must live with long-term stress

2. Explain the environmental causes of depression
Synthetic chemicals, in the form of food additives and preservatives, pesticides, hormones and drugs, and industrial byproducts, are bombarding our bodies at an unprecedented rate. In this article, we use the term "environmental causes" to describe environmental contributions to depression which are present in our environment in the form of air, water and food pollution. Other non-chemical sources of environmental stress include noise pollution, electrical pollution natural disasters, and other catastrophic environmental events. Although some authors consider events like childhood abuse, prolonged stress at home or work, coping with the loss of a loved one, or traumatic events as environmental, we classify them as social and relational causes of depression.

3. Explain the cognitive causes of depression.
http://www.mentalhelp.net/poc/view_doc.php?type=doc&id=13012&cn=5
http://www.healthyplace.com/depression/main/causes-of-depression/menu-id-943/