Canada — McMaster HEI systematic reviews

McMaster’s evidence institute (HEI) published systematic reviews of sex-rejecting procedures, grading how sure we can be about the results (GRADE). The HEI department page does not list the papers one by one; the published reviews are the puberty-blocker and hormone reviews and the mastectomy review. They are not a Canadian government ban.

• Puberty blockers: 10 studies. Evidence comparing treated and untreated youth on everyday function and depression was very weak. Before-and-after evidence on gender dysphoria, function, depression, and bone strength was also very weak. The authors report considerable uncertainty about effects.
• Hormones of the opposite sex under 26: 24 studies. Most comparison evidence was very weak on dysphoria, function, and depression. One comparison study reported somewhat lower odds of depression, still at low certainty. The authors say they cannot rule out benefit or harm.
• Double mastectomy under 26: 39 studies. Comparison and before-and-after evidence ranged from low to very weak, including very weak evidence on gender dysphoria, everyday function, and suicide attempts.
• The HEI authors’ August 2025 statement says only low-certainty evidence exists on the benefits of the treatments they reviewed. That is an evidence finding, not a law.