Sex-Differential Trajectories of Domain-Specific Associations Between Autistic Traits and Co-Occurring Emotional-Behavioral Concerns in Autistic Children.

Assessing autistic traits alongside co-occurring emotional/behavioral concerns (EBCs) is challenging due to their overlap in clinical presentations, which can vary by age and sex. This study aimed to investigate domain-specific associations between autistic traits and EBCs-including anxiety, affective, attention-deficit/hyperactivity, and oppositional-defiant problems-across childhood in autistic boys and girls. We prospectively followed 389 children (84% male) diagnosed with autism at ages 2-5 years, using the Social Responsiveness Scale (SRS) and Child Behavior Checklist (CBCL) across eight timepoints until age 12. Moderated nonlinear factor analysis was used to identify and adjust for measurement non-invariance of SRS items by age, sex, and EBCs. The adjusted scores were then used for sex-moderated time-varying modeling of associations between autistic traits and EBCs. Several SRS items in the domains of social-interaction difficulties and repetitive mannerisms showed significant intercept bias by age and level of co-occurring anxiety and ADHD (effect size r > 0.20). In autistic boys, strong associations were observed between social-communication difficulties and EBCs around ages 7-9, which tended to diminish in late childhood. In contrast, autistic girls showed stable or intensifying associations, particularly with anxiety, into late childhood. Results revealed significant associations between autistic traits and EBCs after addressing item-level measurement biases. The varying associations over time highlight the importance of continuous monitoring to promptly address autistic children's sex-differential mental health needs. These findings emphasize the benefits of refining behavioral constructs and adopting a nuanced developmental approach to identify critical periods of symptom coupling/decoupling for informing evaluation and service provision.