To the Editor: Joost à Campo, M.D., et al. (1) reported that a high proportion of subjects with cross-gender identification suffers from comorbidity with other psychiatric disorders and concluded that their sex reassignment will eventually lead to regret. We are sensitive to the issue that patients may regret their sex reassignment (2, 3). However, we have reason to disagree with the authors since their research suffers from major methods shortcomings.

• A high percentage of psychiatrists (51%) did not return the questionnaire. A likely bias is that those psychiatrists treating patients with a gender identity disorder as a symptom of other psychiatric illnesses completed the questionnaire.

• In total, 584 patients were reported by 142 respondent psychiatrists, many working in the same clinical centers or areas. Patients may have been counted more than once by the different respondents. Our gender clinic treats over 95% of the Dutch gender-dysphoric patients. On the basis of our information on the number of patients consulting a psychiatrist outside our clinic, the number of 584 patients seems unrealistically high unless proven otherwise.

• Psychiatric comorbidity must be assessed reliably by means of validated research instruments and not by the clinical impression or recollection of responders.

• The validity of the conclusions would have been strengthened had the researchers also approached psychologists or general practitioners, who refer the vast majority of patients.

• Patients seen by the psychiatrists in our center are not representative of the average gender-dysphoric patient. Obviously, patients with psychiatric disorders will be most likely to consult a psychiatrist. Therefore, external validity is limited and does not warrant the generalizations the authors made (1).

• The patient study group, not having been chosen randomly from the whole population of transsexuals, was biased. This survey cannot make valid inferences beyond the specific group that was surveyed.

Because of these methods flaws, the authors have no solid data to prove that specialized gender teams would not consider psychiatric disorders as a contraindication to cross-sex hormone treatment, a conclusion easily inferred from their report. The Amsterdam gender clinic has psychiatrists on its staff and adheres to strict procedures, and the majority of transsexual patients benefit from sex reassignment (e.g., references 3–5).