学術誌が画期的なスウェーデンの研究を訂正：再分析で性別手術の精神保健上の利点は見られず

主要研究の修正：「性別肯定」手術が精神的な健康を改善する証拠はない

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 But the new comparison was an afterthought, not part of the original plan, the paper was not withdrawn, and SEGM is a side in the debate.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

2019年の元の研究は、970万人をカバーするスウェーデンの国の健康記録を使い、2005年から2015年に性別不合と診断された2,679人を対象に、2015年の1年間のメンタルヘルス治療を調べました。
ホルモンを使った年数とメンタルヘルス治療の間に関連は見られませんでしたが、最後の手術からの経過が1年増えるごとに治療を受けるオッズは約8%低くなっていました。著者はこれが手術の提供を支持すると述べていました。
スウェーデン、ノルウェー、米国、英国の研究者からの批判的な書簡の後、学術誌の編集者は2回の統計的な再検討を命じ、手術を受けた1,018人と似た状況の手術を受けていない1,018人を比較するよう著者に求めました。
2020年8月の訂正では、この比較は、気分障害や不安での受診、処方、自殺未遂後の入院のいずれについても「手術の利点はない」ことを示したとされました。
訂正は、この研究が人々を時間の経過とともに追跡したわけでも、治療を無作為に割り当てたわけでもないため、手術を支持する結論は「強すぎる」としました。また、手術を受けた人の割合を48%から37.9%に訂正しました。
論文は撤回されず、注記を加えて再掲載されました。著者は返答の中で、手術からの経過時間に関する知見を擁護し、手術を受けていない患者は比較群として適切でないと主張しました。
新たな比較では、手術を受けた人は不安の治療を受ける割合がやや高く、自殺未遂後の入院は13件対7件でした。この差は偶然でも十分に起こりうるもので、SEGMは害を示すものではないとしています。
手術の大半は最近のものでした。1,018人の75%以上が2015年から3年以内で、10年以上前だったのは19人だけだったため、この研究は長期的な結果についてはほとんど何も語っていません。

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

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Abstract

Conclusion