Strong Placebo Effects in ED Drug Trials

MedicalResearch.com Interview with:
Alexander Stridh, MSc
Department of Clinical Neuroscience
Karolinska Institute
Solna, Sweden

MedicalResearch.com: What is the background for this study? What are the main findings?

Response: ​We wanted to investigate how large the effect size is in the placebo arm of clinical trials with PDE5Is for erectile dysfunction.

The major findings in this study is that there is a placebo response in general in ED, though it is hard to tell if this is a genuine placebo effect rather than normal fluctuations in symptom severity among patients.

Another interesting finding was that the placebo response seems largely more important when the cause of ED is mainly due to psychogenic factors, as in post traumatic stress disorder.

Lastly there was an important finding that there was no difference between placebo and active drug with daily treatment of PDE5Is  for long term recovery of erectile function after prostate cancer treatment, a practice which is common in some places and seems to be questionable. 

MedicalResearch.com: What should readers take away from your report?

Response: It is clear that Viagra and other PDE5Is work very well in many cases, but we should not disregard the importance of psychological aspects of ED. Particularly in individuals who have no clear physiological causes for ED. Some patients might benefit better from other interventions, e.g. psychotherapy, than the standard pharmaceutical interventions depending on the individual cause of ED. 

MedicalResearch.com: What recommendations do you have for future research as a result of this work?

Response: ​I would like to see more focus on the cause of the ED in the individual case and that research into treatments are based on this. All drugs have side effects, which in some cases can be severe, and should only be used when absolutely needed.

I would also like to see that the practice of daily treatment with PDE5Is for recovery of erectile function is put into more question since it does not seem like this practice is backed up with solid evidence. It would be of great value if more clinical trials involved a third non-intervention arm that the placebo arm could be compared to. This would provide a better understanding of what would be a placebo effect and what are unspecific responses related to natural fluctuations in symptom severity of a disease.


Stridh A, Pontén M, Arver S, Kirsch I, Abé C, Jensen KB. Placebo Responses Among Men With Erectile Dysfunction Enrolled in Phosphodiesterase 5 Inhibitor Trials: A Systematic Review and Meta-analysis. JAMA Netw Open. 2020;3(3):e201423. doi:10.1001/jamanetworkopen.2020.1423




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Last Updated on March 23, 2020 by Marie Benz MD FAAD