The Depression sometimes runs in families and may be due to heredity, learned behavior or both. Even with a genetic predisposition, it is usually a stressful or unhappy life event that triggers the onset of a depressive episode. While the exact causes of depression are unknown, several factors appear to affect its onset!
I dont think that it was hereditary because this is a personal problem,most of the times we acquired this from being weaker or being bullied by others stronger than us.and this is a serious problem because of many peple commiit suicide just because of depression