Genetic

Depression can occur in people with no family history of the disease. However, there does appear to be some genetic link to depression. Having an immediate family member with depression can increase your risk. Studies of identical twins who were raised in separate homes showed that when one twin was diagnosed with depression, the other twin developed the same disorder 67 percent of the time

Environmental/Psychological

The brain is highly malleable and constantly changing in response to its experiences. That’s in part why scientists believe depression is a product of both our genes and our environment. Traumatic life events, such as the loss of a loved one, distressing financial situations, or big changes like a move can all potentially trigger symptoms of depression.