Childhood abuse (i.e., maltreatment of children and adolescents) represents a severe societal concern, impacting over a third of the population worldwide (Stoltenborgh et al., 2014). Annual incidences are approaching nearly one million children (Sedlak et al., 2010; U.S. Department of Health and Human Services, 2022). Child maltreatment's total lifelong economic impact is now estimated at $2 trillion (Peterson et al., 2018). Childhood maltreatment is typically perpetrated by someone responsible for the child's well-being, with approximately 80 % of cases involving mothers or fathers as the perpetrators (Hughes et al., 2017). Child maltreatment is associated with lifelong adverse biopsychosocial consequences (Chapman et al., 2004; Cicchetti and Handley, 2019). Childhood parental abuse events are additionally linked to increased odds of detrimental impacts on educational attainment and career prospects over long durations (Gilbert et al., 2009; Henkhaus, 2022). Numerous clinicians and scientists have thus long acknowledged the importance of early-life nurture in adulthood mental health since such efforts could identify prevention and treatment targets.

Recent decades of research have substantiated the validity of this proposition. Across 23 longitudinal studies, there was some meta-analytic indication of a dose-response association, with individuals exposed to multiple forms of childhood trauma having over threefold higher odds of developing a psychopathology (McKay et al., 2021). Another meta-analysis of 23 primarily cross-sectional studies showed that the population-attributable fractions (i.e., proportion of cases of a specific health outcome in a population) linked to adverse childhood experiences for increased anxiety, depression, alcohol use disorder (AUD), and substance use disorder (SUD) severity varied between 27.5% and 41.1% across Europe and North America (Bellis et al., 2019). Moreover, epidemiological reports evidenced that childhood parental abuse conferred higher likelihood of developing future increased major depressive disorder (MDD), generalized anxiety disorder (GAD), and panic disorder (PD) severity (Hughes et al., 2017; Scott et al., 2010). Another meta-analysis found that individuals who experienced childhood traumatic events were at an elevated risk of future suicide attempts than the general population (Zatti et al., 2017). Collectively, understanding the mechanisms via which heightened childhood parental abuse might confer increased adulthood psychopathology risk is essential.

Daily stress reactivity and appraisal might be viable mechanisms through which childhood parental abuse predicts increased adulthood psychopathology severity. Myriad biopsychosocial theories postulate that childhood maltreatment might precede stress reactivity, suboptimal stress risk appraisal, and future adulthood psychopathology severity. Biologically, childhood abuse could directly disrupt development within neurobiological stress systems across time (Hakamata et al., 2022). Increased childhood maltreatment could also adversely affect the hypothalamic-pituitary-adrenal (HPA) axis, the primary neuroendocrine system responsible for the stress response (Koss and Gunnar, 2018), and the immune system (Danese and Baldwin, 2017). Psychologically, childhood maltreatment could diminish one's resilience to stress, making them more susceptible to anxious and depressive reactions with lower stress thresholds across extended periods (Shapero et al., 2014).

Ample empirical studies offered evidence consistent with these ideas. Childhood abuse predicted unhealthy thinking patterns that contributed to stress dysregulation, which thereby increased the risk of heightened psychopathology (Weissman et al., 2019). Heightened trait anger expression (internal and external; Win et al., 2021) and reduced self-acceptance (Sanghvi et al., 2023) mediated the relations between increased childhood maltreatment and adulthood depression, anxiety, and SUD severity across 9 to 18 years. Another prior ecological momentary assessment (EMA) study revealed a correlation between a higher frequency of maternal childhood abuse and a heightened perception of daily stressors' severity (Kong et al., 2019). This study further showed that adults who experienced maternal childhood abuse more frequently displayed heightened emotional reactivity in response to everyday stressors. Moreover, individuals with notably reduced positive affect during days with stressors had a higher risk of developing future MDD and anxiety disorders (Rackoff and Newman, 2020). On the whole, existing evidence suggests the plausibility of heightened daily stress reactivity and risk appraisal mediating the pathway of childhood parental abuse predicting increased adulthood psychopathology severity.

Previous research had limitations the current study aimed to overcome. First, most prior studies used cross-sectional or two-wave longitudinal designs. Optimal mediation approaches require three or more time points (Cole and Maxwell, 2003; Maxwell and Cole, 2007) to establish weak causal inference in prospective-observational studies (Blackwell and Glynn, 2018). Second, most prior studies did not separately examine the effects of maternal and paternal abuse. We explored paternal and maternal abuse as distinct predictors, acknowledging that each parent may possess unique caregiving styles and roles within the family, potentially yielding varying effects on a child's future mental health (Cox and Paley, 1997; Cui et al., 2018). Third, high levels of abuse by one parent might be buffered by non-abuse or affection by another, yet interactive effects have not been tested in prior research, which is a gap our study remedied.

Therefore, we focused on addressing a pivotal translational question: identifying targets for mitigating the impact of childhood parental abuse on adulthood psychopathology severity. First, we tested the prediction that increased childhood maternal abuse (Hypothesis 1A) and paternal abuse (Hypothesis 1B) would predict future increased daily stress reactivity, thereby predicting higher GAD, MDD, PD, AUD, and SUD severity. Second, we evaluated the prediction that increased childhood maternal abuse (Hypothesis 2A) and paternal abuse (Hypothesis 2B) would predict future elevated daily stress risk appraisal severity, thereby predicting higher GAD, MDD, PD, AUD, and SUD severity.