A key driver of overdiagnosis in psychiatry/mental health is the accepted wisdom about the adverse outcomes of mental disorders if they are not treated. Claims about untreated mental illness are ubiquitous and influential, not only in psychiatry but also in general practice and the broader medical/health arena, and are used to justify aggressive screening, diagnosis, and potentially harmful treatment of mental disorders. Furthermore, the need for treatment is increasingly being justified in economic terms, in relation to both workplace mental health and global mental health.

However, very few claims about the bleak prognosis of untreated people are actually based on evidence about untreated cases specifically. Many are based on undifferentiated samples of treated and untreated cases, particularly in population studies. Others are based on clinical samples (which of course are much more visible to researchers and clinicians than untreated cases). Often the evidence sources are obscured by secondary/subsequent citation.

A largely neglected body of epidemiological evidence shows that, at a population level, untreated people generally have better outcomes. One of the main reasons for this is confounding – overall, treated people have greater severity and comorbidity. Rates of spontaneous recovery - often related to changes in life stressors/circumstances - are high among untreated people (increasing their invisibility to researchers and clinicians).

Additionally, however, treatment has potential iatrogenic harms, including adverse effects of psychiatric drugs. Evidence about such harms is generally ignored or rationalised ‘on balance’ – or suppressed, as studies such as Restoring 329 have revealed.

The positioning of treatment as the solution to mental disorders not only drives overdiagnosis and inappropriate treatment, but also deflects attention from social determinants of mental health. Socially disadvantaged people are increasingly likely to be seen as being in need of treatment rather than alleviation of poverty, food insecurity, housing insecurity, and so on.

Furthermore, discourses about treated/untreated mental illness are often imbued with not merely wishful thinking but magical thinking. In particular, the word ‘treatment’ is often used symbolically, detached from the reality of clinical and epidemiological evidence, to represent a pathway to a cure and a happy and productive life. Consequently, the ideology of treatment needs to be challenged explicitly, in addition to challenging the misuse of evidence and the neglect of social determinants.