We read with interest this paper ; it is a worthy area of research and this work adds to the understanding of cognitive changes in men with prostate cancer [2–4]. However, we think the study design is fundamentally flawed. The choice of healthy volunteers to act as a control group allows no comment on whether the changes in the prostate cancer group were due to treatment with an LHRH analogue, the shock of their new diagnosis, or the effects of radiotherapy. Is it inconceivable that patients bearing the burden of cancer diagnosis will have cognitive changes, whether or not they are treated with hormonal therapy? We note that previous similar studies have used the same approach [2–4], with a full spectrum of conflicting results. Cognitive functioning either improved , remained unchanged  or declined . If the effects of androgen deprivation were to be taken into account then surely a more appropriate control group would have been patients with prostate cancer undergoing radiotherapy with no adjuvant androgen-deprivation therapy. Only by including such patients as controls can the question in the title be answered.