This study investigates the association between adverse childhood experiences (ACEs) and adult mental health outcomes, adjusting for familial genetic and environmental confounding. Using a Swedish twin cohort study, researchers analyzed data from 25,252 twins aged 18-47 years, assessing exposure to 7 types of ACEs, including family violence, emotional abuse, physical neglect, physical abuse, sexual abuse, rape, and hate crime. Adult mental health outcomes were determined from the Swedish National Patient Register, including diagnoses of depression, anxiety, alcohol or drug misuse, and stress-related disorders. The study found that a greater number of ACEs was associated with increased odds of any psychiatric disorder, with the association remaining significant even after adjusting for familial factors. The association was most pronounced in cases of multiple ACEs or sexual abuse. In discordant twin pair analyses, the association remained, but the odds ratios were attenuated, suggesting that familial factors contributed to the observed associations. The study highlights that while ACEs are strongly linked to adult mental health outcomes, familial confounding, including genetic and environmental factors, also plays a role. These findings suggest that targeted interventions may help reduce the risk of future psychopathology. However, the study also indicates that family-wide risk factors, such as genetic predisposition and socioeconomic disadvantage, may contribute to adult mental health outcomes among individuals who experienced ACEs. The study's results support the need for interventions targeting both individual and family-level risk factors.This study investigates the association between adverse childhood experiences (ACEs) and adult mental health outcomes, adjusting for familial genetic and environmental confounding. Using a Swedish twin cohort study, researchers analyzed data from 25,252 twins aged 18-47 years, assessing exposure to 7 types of ACEs, including family violence, emotional abuse, physical neglect, physical abuse, sexual abuse, rape, and hate crime. Adult mental health outcomes were determined from the Swedish National Patient Register, including diagnoses of depression, anxiety, alcohol or drug misuse, and stress-related disorders. The study found that a greater number of ACEs was associated with increased odds of any psychiatric disorder, with the association remaining significant even after adjusting for familial factors. The association was most pronounced in cases of multiple ACEs or sexual abuse. In discordant twin pair analyses, the association remained, but the odds ratios were attenuated, suggesting that familial factors contributed to the observed associations. The study highlights that while ACEs are strongly linked to adult mental health outcomes, familial confounding, including genetic and environmental factors, also plays a role. These findings suggest that targeted interventions may help reduce the risk of future psychopathology. However, the study also indicates that family-wide risk factors, such as genetic predisposition and socioeconomic disadvantage, may contribute to adult mental health outcomes among individuals who experienced ACEs. The study's results support the need for interventions targeting both individual and family-level risk factors.