Prevalence and Factors Associated with Overweight and Obesity in Thai Children and Adolescents with Autism Spectrum Disorder: A Retrospective Longitudinal Study

Children with Autism Spectrum Disorder (ASD) exhibit higher rates of overweight/obesity compared to children without ASD, yet influencing factors remain inconclusive. This study aimed to evaluate the prevalence of overweight/obesity and identify associated factors within this population using longitudinal data. This retrospective longitudinal study analyzed 1,876 visits from 176 children and adolescents (aged 2–18 years) diagnosed with ASD attending a child psychiatric clinic between 2012 and 2018. World Health Organization (WHO) criteria defined weight status. Generalized Estimating Equations (GEE) and linear regression identified factors associated with overweight/obesity and Body Mass Index (BMI) Z-scores. The overall prevalence of overweight/obesity was 35%, increasing significantly from 27.3% (initial visit) to 37.5% (last visit), alongside rising BMI Z-scores (p < 0.001). Antipsychotics use showed a modest association with increased odds of overweight/obesity (Adjusted Odds Ratio [AdjOR] = 1.499, p = 0.049). Age (β = − 0.100, p = 0.037), stimulants use (β = − 0.312, p = 0.030) and mood disorders (β = − 0.982, p < 0.001) correlated with lower BMI Z-scores, while Attention-Deficit/Hyperactivity Disorder (ADHD) (β = 0.442, p = 0.027) correlated with higher scores. Children with ASD show higher prevalence of overweight and obesity than children without ASD. Identified associations between psychotropic medications, comorbid psychiatric conditions (mood disorders, ADHD), and weight status underscore the critical need for early psychiatric assessment, proactive weight monitoring, and tailored management strategies in this vulnerable population.