The paper by Falkenberg and colleagues ^{Reference Falkenberg, Benetti, Raffin, Wuyts, Pettersson-Yeo and Dazzan1} on the clinical use of magnetic resonance imaging (MRI) in first-episode psychosis (FEP) is of great interest, but several critical notes need to be made.

First, a stated aim of this study was to investigate whether MRI assessment of people with FEP is feasible in the majority of patients. We agree with the authors that this is indeed the case for the large majority of patients, despite the possibility of some selection bias; however, we wonder why the authors did not provide any further information on why the scanning of 2.5% of patients with FEP in the clinical sample could not be completed. What were the reasons? This information would have been very informative, especially from a clinical perspective.

Second, we do not understand why the authors did not control for gender in the clinical sample, particularly because they use previously collected data. It was shown long ago that gender ^{Reference Nasrallah, Schwarzkopf, Olson and Coffman2} is an important factor in MRI research in schizophrenia. It has, for instance, been suggested that the significant differences between male and female patients with schizophrenia arise from the interplay of sex hormones, neurodevelopmental and psychosocial sex differences, ^{Reference Leung and Chue3} and it is therefore strange that the authors did not explain why they decided not to control for it.

Third, we found the second hypothesis very unspecific. What do the authors mean exactly by ‘a substantial proportion’? It is unclear what percentage of the patients had to show radiological abnormalities in order to prove or reject the hypothesis.

Finally, on what criteria do the authors draw the conclusion that an MRI scan is indicated in the clinical assessment of all patients presenting with FEP? In particular, if one takes into account the cost-benefit analysis that they mention in the introductory section of their paper, this conclusion seems unfounded. The point here is that if one does not apply strict cost-benefit criteria, one can also make the claim for preventive scanning of everyone in society to detect early tumours, encephalitis, and so on.