Therapy is effective, but not always. sometimes, especially with children, there is no root cause in life to the depression beyond "genetics". Additional, therapy may simply be useless and unproductive without medication being used concurrently.

There's also simply death. I didn't feel like mentioning it, but I think its worth pointing out that without treatment, death is a very real possibility.

>sometimes, especially with children, there is no root cause in life to the depression beyond "genetics".

I find this hard to believe. People in the past weren't depressed nearly as much, so whatever is causing it has to be environmental.

Do we know that, though? Historically the lives of most people were bleak and miserable. You don't really have much time to feel depressed when you have to work for 14 hours in a factory 6 days a week or lose your home and eventually die in the streets due to malnutrition and disease. People who couldn't take care of themselves and didn't have a support network just didn't live that long and/or were entirely erased from history...

People in the past couldn't get a diagnosis, so they had to settle for cirrhosis.