b'What are the causes of MDD? There is no single known cause. Psychological, biological, and environmental factors all contribute to its development. Norepinephrine, serotonin, and dopamine are three neurotransmitters (chemical messengers that transmit electrical signals between brain cells) that are thought to be involved. Antidepressant medications work by increasing the availability of neurotransmitters or by changing the sensitivity of the receptors for these chemical messengers. Thought processes, behaviors and interpersonal relationships also play a role in MDD. Various psychotherapies have been found to effectively treat MDD including cognitive therapy, interpersonal therapy and behavioral activation. Genetics may also play a role. There is an increased risk for developing depression when there is a family history of the illness. Some people may have a biological make-up that leaves them particularly vulnerable to developing depression. Life events such as the death of a loved one, a major loss or change, chronic stress and alcohol or drug abuse may trigger episodes of depression. Some illnesses such as heart disease and cancer and some medications may also trigger depressive episodes. How is MDD treated? Although MDD can be devastating, it is highly treatable. Between 80 and 90 percent of those diagnosed with MDD can be effectively treated and function normally. Many types of treatment are available and the type chosen depends on the individual and the severity and patterns of the illness.Mental Health Concerns161'