Depression seems to run in families and from generation to generation. This is why some have concluded depression to be a genetic disorder a ‘disease’. However no gene has ever been located for depression and it seems more likely that depression (consisting of a set of attitudes) is contagious see this article. We know that attitudes are contagious. For example negativity can seep through a work place causing low morale. Fortunately we have put stringent safe guards in place and that has not happened here at Uncommon Knowledge : )
Low morale can also run in families.

Pessimism, worry and catastrophising all have chemical consequeces in the brain which have led people to confuse causes and consequences. Attitudes don’t just affect the mind but also the body. So we could say depression is a series of learned attitudes having physical consequences see The depression learning path

Just as superstitious beliefs can run in families so too can pessimistic ones. Partners of depressed people are more likely themselves to experience some level of depression partly because it’s distressing to see a loved one distressed but also because depressing attitudes are infectious (like any black or white ideas). This is not to say that no depressions have physical causes but I think it’s important for us to understand how influenced we are by one another. It’s also more hopeful in that it can be easier to work on attitude than on genetic heritage.

Mark.

Related: Depression Recovery Program