I believe depression is made up of different types.

Some do have forms that can be treated with medication due to chemical imbalances.

Many have been brought up to process thoughts unhelpfully.
For some this can be corrected with therapy eg. CBT
However many here suffer much more and meds and CBT are not enough.

We learn tools to manage our limited lives but struggle day to day with issues that others manage well.
We are rejected by society which makes our health even worse.

Maybe one day we will have better treatments, I hope so, very much.