Tsou (2016) makes a case for natural kinds of mental disorders. This seems to be dependent on his claim that there is "good evidence that the symptoms of schizophrenia are underwritten by stable neurobiological mechanisms". By this he means the dopamine theory of schizophrenia. Similarly he says "multiple lines of research indicate that the core signs of depression are underwritten by stable neurobiological mechanisms". Again, by this he means the monoamine hypothesis of depression. I guess if the dopamine and monoamine hypotheses are incorrect, his whole argument fails.
He does acknowledge the article by Kendler and Schaffner (2011) that I have mentioned before (eg. see previous post). This apparently doesn't undermine his faith in the dopamine hypothesis. The monoamine hypothesis is similarly not tenable (eg. see previous post). Even psychiatrists have described the 'chemical imbalance theory' as a kind of urban myth (see previous post and book review). Psychopharmacologists stopped believing in it a long time ago.
Tsou wishfully hopes that "mental disorders should be classified at a level of generality such that the characteristic signs of disorders are associated with stable biological mechanisms". His lack of clinical and scientific experience does not provide a sound basis for his philosophical theorising. Psychiatric diagnosis is inevitably purely descriptive. Considering the motivation for the revision of DSM-5 (see eg. previous post), information about the biological causes of mental disorders would have been incorporated if there is any, which there isn't.