Prosser and colleagues ^{Reference Prosser, Helfer and Leucht1} argue that any distinction between pharmacotherapy and psychotherapy is a fallacy, as both treatment modalities ultimately target underlying disturbances in neural circuitry. However, the justification of psychotherapy on the basis of its ability to deliver neurobiological changes, as the authors argue, is flawed. Specifically, they assume that mental disorders are simply brain diseases and that behavioural aberrations can be accounted for by disordered neurobiological processes. Despite the tremendous resources dedicated to uncovering the biological basis of mental illness, we have yet to identify a reliable biomarker for any mental disorder. ^{Reference Deacon2} Therefore, proposed mechanisms of neurobiological actions of psychotherapy for mental illness are reductionistic at best and highly speculative at worst.

The reformulation of psychotherapy as a neurobiological treatment is yet another example of the creeping trend towards neuroessentialism. ^{Reference Reiner, Iles and Sahakian3} The evidence for the efficacy of psychotherapies in the treatment of mental disorders stands by itself, and grounding this in speculative theories of its neurobiological action has no added value. Further, the authors seem to equate psychotherapy with cognitive–behavioural therapy, although a number of other therapies, including psychoanalytic psychotherapy, have demonstrable efficacy, ^{Reference Fonagy, Rost, Carlyle, McPherson, Thomas and Pasco Fearon4} with the therapeutic effects best conceptualised as occurring through the therapeutic relationship rather than reductionistic neural mechanisms.

Although the authors have the noble aim of championing the role of psychotherapy in the contemporary treatment of mental illness, privileging a biological model of mental disorder may actually reduce clinicians' empathy for their patients. ^{Reference Lebowitz and Ahn5} In this way, reducing psychotherapy to simply a biological treatment may undermine its effectiveness. Instead, treatments should be evaluated on the weight of the evidence of their efficacy alone.