"She Felt Better. Then She Did Not. — The Placebo Effect of Incomplete Endometriosis Surgery and Why Pain Always Returns When Disease Remains"
In 1999, a landmark randomised controlled trial published in the New England Journal of Medicine examined patients with knee osteoarthritis who underwent either real arthroscopic surgery or a sham procedure — an incision made, a camera inserted, and nothing else done. The results were striking and deeply uncomfortable for the surgical community — patients who received the sham surgery reported pain relief equivalent to those who received the real procedure. The placebo effect, it turned out, was a remarkably powerful surgeon.
Endometriosis surgery has its own version of this uncomfortable conversation — and it is one the field has been slow to have openly.
The Sutton Trial — Endometriosis Surgery's Inconvenient Truth
The most cited evidence of placebo effect in endometriosis surgery comes from a 1994 randomised controlled trial by Sutton and colleagues — one of the very few sham-controlled surgical trials ever conducted in gynaecology. Women with confirmed endometriosis were randomised to either laser ablation of their lesions or a diagnostic laparoscopy alone — the surgical equivalent of looking without touching. At six months follow up, 62% of women in the treatment group reported significant pain improvement — but so did 22% of women in the sham surgery group. The disease in the sham group was untouched. And yet nearly one in four women felt meaningfully better.
This finding is not an argument against endometriosis surgery. It is an argument for understanding pain in its full complexity — biological, neurological, and psychological — and for ensuring that when surgery is offered, it is complete enough to deliver results that genuinely exceed what the mind alone can achieve.
What the Placebo Effect Is Really Telling Us:
The placebo effect in endometriosis surgery is not evidence that the pain is imaginary. It is evidence that pain is extraordinarily complex. The expectation of relief, the ritual of anaesthesia and surgery, the care of a medical team, and the psychological permission to rest and recover — all of these are neurologically active experiences that genuinely modulate pain perception in measurable, meaningful ways.
For the endometriosis surgeon, the placebo effect carries an important and humbling message — that some of the apparent success of incomplete surgery may not be surgical success at all. A patient who feels better for six months after an ablation that left disease behind may be experiencing the placebo response of surgery rather than the genuine therapeutic effect of complete disease removal. When her pain returns at twelve months, it is not the endometriosis recurring — it is the placebo effect wearing off, and the persistent disease reasserting itself.
The Implications for Surgical Standards:
The existence of a placebo effect in endometriosis surgery does not level the playing field between complete excision and incomplete ablation. It raises the bar. If incomplete surgery can produce short term improvement through placebo mechanisms alone, then the true measure of surgical success must be long term — sustained pain relief, reduced reoperation rates, improved quality of life at two, five, and ten years. And on every one of those long term measures, complete expert excision outperforms incomplete surgery decisively.
The placebo effect is a short term phenomenon. Complete excision is a long term solution. The difference between them is measured not in the recovery room — but in the years of a woman's life that follow.
What This Means for Patients:
If you have had endometriosis surgery and felt better initially, only to have your pain return months later — you were not imagining either experience. The initial relief was real, neurologically genuine, and entirely explainable. The return of pain is equally real — and equally explainable, by disease that was never fully removed and a placebo response that was never going to last.
You deserved surgery complete enough that its results did not depend on the placebo effect to sustain them. You may still deserve that surgery. And knowing the difference between temporary relief and genuine, complete surgical treatment is the first step toward asking for — and receiving — the care that will actually last.
The placebo effect proves that the mind is a powerful healer. Complete excision proves that the surgeon's hands can do what the mind alone cannot sustain. The goal of endometriosis surgery should always be the latter — because the patient deserves relief that does not have an expiry date.
The placebo effect proves that the mind is a powerful healer. Complete excision proves that the surgeon's hands can do what the mind alone cannot sustain. The goal of endometriosis surgery should always be the latter — because the patient deserves relief that does not have an expiry date.
Salman Okour,MD