I agree strongly with your notion that psychiatry is based on models, and hasn't fully captured some underlying reality, and most of the psychiatrists that I know would concur. That's why we're continually trying to improve and refine those models.

But most of these models (depression, ADHD, PTSD) do seem to fit with human cultures around the world. The convergence of such different cultural conditioning into so many of the same conditions suggests some strong biological propensities in those directions.