Numerous factors can cause depression. Genetics may play a role, for example, in the onset of depression, as can hormones, traumatic events, and even reduced exposure to sunlight. Although not an all-inclusive list, the common causes of depression include some of the following issues.
Your genetics may make you more likely to over or under-produce the brain chemicals implicated in depression. If your parents or siblings tend to experience depression, you're more likely to do so as well.
Even having extended family members -- like aunts or uncles -- with a history of depression can indicate a genetic component. Researchers have not yet pinpointed the exact genes that cause depression.
Imbalanced Brain Chemistry
Depression can not only result from an imbalance of chemicals in the brain, but it can also lead to this imbalance after being triggered by another factor, like a traumatic event. The main chemicals -- or neurotransmitters -- responsible for mood regulation are dopamine, serotonin, and norepinephrine. Sometimes the brain doesn't produce these chemicals in sufficient quantities. Other times, there's an adequate supply of these neurotransmitters, but the brain's neurons simply aren't reacting to them appropriately.
Each neurotransmitter also plays a role in other bodily functions, like sleep or digestion. Your specific depression symptoms can help a behavioral health professional pinpoint the chemical that's causing your depression.