The prevalence of self-harm was also examined in the full sample and across four groups, which differed in concordance and exposure to EAU. The prevalence of SA and NSSI was significantly higher in twin pairs concordant for EAU and in the EAU exposed twin in discordant pairs relative to twin pairs concordant for no EAU and unexposed twins in discordant twin pairs. However, there were no significant differences in the latter two groups, which would be expected if shared predispositions were strongly influencing the co-occurrence of EAU and self-harm. Importantly, the elevated rates of both SA and NSSI among EAU exposed twins from discordant pairs relative to their unexposed co-twin suggest that the link between these phenotypes is either causal or due to individual-specific factors. In other words, if there were shared familial factors strongly influencing EAU and self-harm, it would be expected that twin pairs - who share genes and the familial environment - would exhibit similar rates of self-harm regardless of exposure to EAU, which was not the case. Importantly, however, these analyses did not differentiate between MZ
