Abstract: Childhood environmental unpredictability, defined as the spatial-temporal variation of adverse experiences, has been identified as an essential feature of adversity that has important developmental implications. Prior work has linked environmental unpredictability to mental health problems and dysregulation of the hypothalamic- pituitary-adrenal (HPA) axis. However, most studies have treated unpredictability as a static construct, overlooking variability in environmental experiences over time. Although the distinct effects of the two dimensions of childhood adversity (i.e., threat and deprivation) on adolescent outcomes are well-established, the unique characteristics of unpredictability within these dimensions remains poorly understood. Furthermore, resilience factors that may buffer the negative effects of environmental unpredictability have received little attention. To address these gaps, the present study investigated how unpredictability related to threat (i.e., abuse) and deprivation (i.e., neglect) predicts adolescents’ diurnal cortisol rhythms and depressive symptoms, and whether a positive school climate moderates these associations.
The sample consisted of 211 adolescents (T1: M_age = 10.82 years, SD = 0.85; 34.6% girls) who participated in a four-wave longitudinal survey spanning two years. Linear mixed models (LMMs) were estimated to capture trajectories of adversity exposure, and the residuals (the differences between predicted and observed values) at each time point were used to compute the root mean squared error (RMSE) as an indicator of unpredictability in abuse and neglect. Linear regression analyses were then conducted to test both main and interaction effects. For significant interaction effects, the Johnson-Neyman technique was applied to plot the simple slopes across the full range of the moderator.
Results indicated that unpredictability in abuse significantly predicted flatter diurnal cortisol slopes but not depressive symptoms. A significant interaction with average abuse levels was observed, such that unpredictability in abuse was associated with fewer depressive symptoms when average abuse exposure was high. Unpredictability in neglect showed no significant associations with either diurnal cortisol rhythms or depressive symptoms. School safety and order moderated the link between abuse-related unpredictability and diurnal cortisol slopes, such that unpredictability in abuse was associated with flatter slopes only when perceived school safety and order were low. Similarly, school support and acceptance moderated the association between neglect-related unpredictability and diurnal cortisol slopes, with effects evident only when school support and acceptance were low.
Findings revealed distinct effects of unpredictability within threat (i.e., abuse) and deprivation (i.e., neglect). Specifically, abuse-related (but not neglect-related) unpredictability predicted flatter diurnal cortisol rhythms, above and beyond the effects of average abuse levels. Moreover, the impact of abuse-related unpredictability varied by the average levels of abuse exposure, highlighting the importance of considering broader contextual features including environmental severity, in understanding developmental consequences. A positive school climate has emerged as a resilience factor, with significant implications for both educational practice and policy. Enhancing school safety and order may be particularly effective in buffering the negative consequences of abuse-related unpredictability for adolescent health, whereas strengthening teacher-student support and acceptance may better mitigate the negative effects of neglect-related unpredictability.

Key words: family environmental unpredictability, HPA axis, depressive symptoms, resilience factors, school climate