Causes
Some types of depression are similarly experienced among family members, suggesting an inheritable genetic vulnerability. In some instances, major depression can be traced across generations. However, it can also occur in people with no family history of depression. Whether inherited or not, major depressive disorder is often associated with changes in brain structures or brain function.
Risk factors for the development of depression can also include personality characteristics, such as low self-esteem, a pessimistic view of oneself and the world, and vulnerability to stress. It is currently unclear whether these triggers represent a form of psychological predisposition or rather an early appearance of the illness. Furthermore, profound loss, strained relationships, financial difficulties, or any stressful (unwelcome or even desired) modifications to daily life can trigger a depressive episode.
Recently, researchers have illustrated that physical changes in the body can be accompanied by mental change as well. Medical afflictions such as stroke, a heart attack, cancer, Parkinson's disease, and hormonal disorders can lead to the development of a depressive episode(s), often perpetuating feelings of indifference and hopelessness, thus lengthening the recovery process.
Very often, a combination of genetic, psychological, and environmental factors is involved in the onset of a depressive disorder. Once a single depressive episode is experienced, subsequent episodes can be readily triggered by only mild stressors or none at all.