Mood disorders are hereditary.
Mood disorders do run in families and if someone in your family such as your mother or father has a mood disorder then it's very likely that the son or daughter will have a mood disorder as well.
The trait or conditions that cause mood disorders are often both caused by environmental conditions as well has being inherited.
The mood disorders are thought to be caused by a mix of genes by both parents.
Mood disorders such as clinical depression, depression and even Bipolar Disorder are hereditary and are passed down through the genes of either one or both parents.
However it still is possible to get mood disorders and be Bipolar and have clinical depression or even just plain old depression when none of your parents suffer from those conditions.
So yes you can inherit those conditions but you can also get those mood disorders without having them passed down to you from family or parents.