Une revue corrige une étude suédoise majeure : la réanalyse ne trouve aucun bénéfice mental de la chirurgie

Correction d'une étude clé : Aucune preuve que les chirurgies « d'affirmation de genre » améliorent la santé mentale

Commentaire & analyse Chirurgie Santé mentale & suicide

Authors: Society for Evidence-Based Gender Medicine (SEGM)
Journal: Society for Evidence-Based Gender Medicine (SEGM)
Year: 2020
Source: segm.org/ajp_correction_2020

Summary

A 2019 Swedish study by Bränström and Pachankis in the American Journal of Psychiatry was widely reported as showing that gender surgery improves mental health. People whose surgery was longer ago were less likely to be getting mental health care in 2015; hormones showed no such link. After critical letters, the journal asked statisticians to review it and asked the authors to compare 1,018 surgery patients with 1,018 similar people who had not had surgery. That comparison showed 'no advantage of surgery'. The 2020 correction called the pro-surgery conclusion 'too strong' and fixed a 48% vs 37.9% error. This SEGM (Society for Evidence-Based Gender Medicine) article explains the correction accurately. But the new comparison was an afterthought, not part of the original plan, the paper was not withdrawn, and SEGM is a side in the debate.

Key findings

L'étude initiale de 2019 utilisait les dossiers de santé nationaux suédois couvrant 9,7 millions de personnes, dont 2 679 diagnostiquées d'incongruence de genre entre 2005 et 2015, et examinait les traitements de santé mentale sur une seule année, 2015.
Elle ne trouvait aucun lien entre les années sous hormones et les traitements de santé mentale, mais environ 8 % de probabilités en moins d'être traité pour chaque année écoulée depuis la dernière chirurgie. Les auteurs affirmaient que cela soutenait le recours à la chirurgie.
Après des lettres critiques de chercheurs de Suède, de Norvège, des États-Unis et du Royaume-Uni, le rédacteur en chef de la revue a ordonné deux examens statistiques et demandé aux auteurs de comparer 1 018 patients opérés avec 1 018 patients non opérés similaires.
La correction d'août 2020 indiquait que cette comparaison ne montrait « aucun avantage de la chirurgie » pour les consultations pour troubles de l'humeur ou anxiété, les prescriptions ou les hospitalisations après tentative de suicide.
La correction qualifiait la conclusion en faveur de la chirurgie de « trop forte » parce que l'étude ne suivait pas les personnes dans le temps et n'attribuait pas les traitements au hasard. Elle corrigeait aussi la part de personnes opérées, de 48 % à 37,9 %.
L'article n'a pas été retiré. Il a été republié avec une note ajoutée, et dans leur réponse les auteurs ont défendu le résultat sur le temps écoulé depuis la chirurgie et soutenu que les patients non opérés sont un mauvais groupe de comparaison.
Dans la nouvelle comparaison, les patients opérés étaient un peu plus souvent traités pour anxiété, et avaient 13 hospitalisations après tentative de suicide contre 7. Cet écart pourrait facilement être dû au hasard, et le SEGM dit qu'il ne montre pas de préjudice.
La plupart des chirurgies étaient récentes : plus de 75 % des 1 018 dataient de moins de trois ans avant 2015 et seulement 19 de 10 ans ou plus, si bien que l'étude dit peu de choses sur les résultats à long terme.

Abstract

In October 2019, the American Journal of Psychiatry (AJP) published a study from the Karolinska Institute in Sweden, and the Yale School of Public Health which reported that “gender-affirming" surgeries for gender dysphoric patients are associated with improved mental health outcomes. Looking at mental health utilization in the year 2015, a retrospective analysis showed that the more time passed since surgery, the fewer mental services were utilized by patients, with an average 8% reduction in mental health utilization for each year following surgery. From this, the study concluded that surgery has a beneficial effect on mental health, and that benefits continue to accrue over time. However, following a reanalysis of the data, this conclusion has now been officially corrected to indicate that there is “no advantage of surgery.”

Conclusion

After reanalysis with a control group comparing gender dysphoric patients who received surgery to those who did not, no statistically significant difference was found in mental health utilization measures. The AJP correction stated the original conclusion that 'the longitudinal association between gender-affirming surgery and lower use of mental health treatment lends support to the decision to provide gender-affirming surgeries' was too strong. The Society for Evidence-Based Gender Medicine (SEGM) concluded that no mental health benefit of gender-affirming surgery was demonstrated in the corrected analysis.

Methodological limitations

Written by a group with a position: This record is SEGM's explanation, not the correction itself. SEGM argues for caution in gender medicine and notes that some of its advisers wrote the critical letters, so its framing should be read with that in mind.
New comparison was an afterthought: The surgery vs no-surgery comparison was not part of the original question. The correction notes that the groups may differ in several other ways, so the 'no difference' result is also not strong proof either way.
Comparison group mixes different people: The authors argued that people diagnosed with gender incongruence who had not had surgery include many who never wanted it. So finding no difference does not show surgery has no benefit for those who seek it, a point SEGM accepts.
Corrected, not withdrawn: The journal corrected the conclusion and reposted the article, but did not withdraw the time-since-surgery link, which the authors stood by. Saying 'the study was wrong' goes further than the formal correction.
One-year snapshot: Both analyses looked at mental health treatment in 2015 only, comparing different people at different times since surgery rather than following the same people over time. They cannot show change in any one person.
Indirect measures: Visits, prescriptions and hospital stays measure use of services, not symptoms or quality of life. Required mental health assessments before surgery may have pushed up service use around the time of surgery.
Deaths and moves abroad missed: Only people alive and living in Sweden in 2015 were included. If people died, including by suicide, after surgery, those with surgery long ago would look healthier than they were. The authors admitted this.
Patients changed over time: More recent patients were younger, more often born female and more often had other mental health problems. This alone could explain why people with older surgeries used fewer services, regardless of surgery.
Many tests, one hit: The single positive result in the original was only just clear of chance, and came alongside several other measures tested without allowing for the extra chance of a fluke, as letter writers pointed out.
Doubtful 'lost patients' claim: SEGM suggests about 90% of patients were 'lost', because only 19 had surgery before 2005 compared with 324 in an earlier Swedish study. But the study only included people diagnosed from 2005 to 2015, so people treated earlier were mostly outside the study rather than lost.
Too few suicide-related cases: Hospital stays after suicide attempts (13 vs 7) are too few to support conclusions either way, and the new comparison was too small to test this properly.

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Summary

Key findings

Abstract

Conclusion