Men with erectile dysfunction (ED) who were in the placebo arm of clinical trials of phosphodiesterase 5 inhibitors (PDE5Is) had significant improvement in erectile function, with a more pronounced effect among men with posttraumatic stress disorder (PTSD) according to a recently published systematic review and meta-analysis.

In addition, phosphodiesterase 5 inhibitors (PDE5Is) did not differ significantly from placebo in their effect on erectile function among men who experience ED following prostate surgery or radiotherapy.

“The findings suggest that contextual factors are important in the delivery of care to patients with sexual dysfunction, and the lack of difference in response between placebo and [PDE5Is] in certain patient subgroups suggests that clinical practice should change,” Alexander Stridh, MSc, of the Karolinska Institute in Stockholm, Sweden, and colleagues wrote in JAMA Network Open.

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The systematic review and meta-analysis included 63 double-blind, placebo-controlled trials of PDE5Is for ED that enrolled a total of 12,564 men. The main outcome was improvement in the erectile function domain of the International Index of Erectile Function questionnaire.

In background information, the authors observed: “Given the reputation of this class of drugs, it seems possible that some of the effects of the drugs may be related to the power of belief.”

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As for the larger placebo effect among men with PTSD, the authors wrote: “Assuming that ED in this patient group was associated with psychological stress caused by traumatic experiences, the large improvement in the placebo arm could indicate that psychological factors might be associated with ED symptom improvements.”


Stridh A, Pontén M, Arver S, et al. Placebo responses among men with erectile dysfunction enrolled in phosphodiesterase 5 inhibitor trials. A systematic review and meta-analysis.

JAMA Netw Open. 2020 Mar 2;3(3):e201423. doi: 10.1001/jamanetworkopen.2020.1423.