Yeah, the DSM got worse to the point that the NIMH and Thomas Insel rejected it as pseudo-scientific. So, the DSM is invalid and the DSM categories can't reliably be diagnosed by clinicians. That is the basis idiot :

Published in the journal Neuron, Raymond Dolan—considered one of the most influential neuroscientists in the world—co-authored “Functional Neuroimaging in Psychiatry and the Case for Failing Better,” concluding, “Despite three decades of intense neuroimaging research, we still lack a neurobiological account for any psychiatric condition.”

Reflecting on the more than 16,000 neuroimaging articles published during the last 30 years, Dolan and his co-authors concluded: “It remains difficult to refute a critique that psychiatry’s most fundamental characteristic is its ignorance. . . . Casting a cold eye on the psychiatric neuroimaging literature invites a conclusion that despite 30 years of intense research and considerable technological advances, this enterprise has not delivered a neurobiological account (i.e., a mechanistic explanation) for any psychiatric disorder, nor has it provided a credible imaging-based biomarker of clinical utility.”

In 2011, establishment psychiatrist Ronald Pies, Editor-in-Chief Emeritus of the Psychiatric Times, stated: “In truth, the ‘chemical imbalance’ notion was always a kind of urban legend—never a theory seriously propounded by well-informed psychiatrists.”

Anyway, the onus of proof is not on 'mental illness' deniers but on the people who proclaim it exists with no scientific proof :

There is no evidence for the supposed “science” of psychiatry. There is no test for any mental illness, no proof of causation, no evidence of successful “treatment” that relates specifically to an individual disorder, and no accurate prediction of future cases. Thus, the claim that psychiatric constructs are real disease has not been proven.