The tetrachoric correlation between NSSI and SA was .53 (p<.01). Of the 6,082 twins retained in the final sample, 247 (4.1%) reported a history of NSSI only, 144 (2.4%) reported SA only, and 59 (1.0%) participants endorsed a history of both NSSI and SA. The mean age of SA onset was 21.12 years (median=20.0). EAU was significantly associated with both NSSI and SA, with ORs of 2.41 (95% confidence interval [CI]: 1.89-3.07; p<.01) and 2.35 (95% CI: 1.75-3.15, p<.01), respectively (see Supplemental Table 1 for parameter estimates and test statistics).
