a) Much of the brain is not understood. Including why consciousness happens.
b) Even if scientists know the cause of mental health problems, that doesn't mean they can treat those causes. Every human who lives long enough will die of a non-treatable disease. Understanding a problem does not imply treatment is possible.
> Understanding a problem does not imply treatment is possible.
correct. But it seems to me like mental health practitioners artificially limit their diagnosis to conditions which can be treated with an FDA-approved pill, when an old-fashioned quaker asylum [0] would be more appropriate.