The cause of a<unk>  is not well understood. However, the mechanism is believed to be a combination of biological, psychological, and social factors. A<unk>  can often follow an acute stress in someone's life. Evidence suggests that psychosocial stressors play a larger role in the first 1-2 depressive<unk> s, while having less influence in later<unk> s. People who experience a<unk>  often have other mental health issues. Other risk factors for a depressive<unk>  include: * Family history of a mood disorder * Recent negative life events * Personality (insecure, worried, stress-sensitive, obsessive, unassertive, dependent) * Early childhood trauma * Postpartum * Lack of interpersonal relationships Studies show that depression can be passed down in families, but this is believed to be due to a combined effect of genetic and environmental factors. Other medical conditions, like hypothyroidism for example, may cause someone to experience similar symptoms as a<unk> , however this would be considered a mood disorder due to a general medical condition, according to the DSM-V.
Major depressive episode
Major depressive disorder
Outline of bipolar disorder
Depression 
Late life depression
Atypical depression
Postpartum psychosis
Postpartum depression