What is the root cause of depression? That's a huge subject, and for some people even with community and a job and hobby they still feel depressed. Sometimes the underlying condition really is a chemical imbalance.

For example, adverse childhood experiences are highly correlated with depression. What's the underlying problem to tackle with a 50 year old adult who is depressed as a result of abuse as a child? Some things just change you and no amount of therapy can undo that