# Antipsychotic Treatment and Longitudinal Body Mass Index Trajectories in Youth with and Without Autism Spectrum Disorder

## TL;DR

This study examines how antipsychotic treatment affects weight changes in children with and without autism over time.

## Contribution

The study provides new insights into BMI trajectories in youth with autism on antipsychotics compared to those without autism.

## Key findings

- BMI z-scores increased over time, with baseline BMI being the strongest predictor.
- Youth with autism started antipsychotics earlier, but no significant difference in BMI change rate was found.
- Weight trajectories highlight the need for metabolic monitoring in treated youth.

## Abstract

Background: Children and adolescents with autism spectrum disorder (ASD) frequently receive antipsychotics and are considered at increased risk for weight gain. Few studies have compared longitudinal weight trajectories between youth with ASD and those with other psychiatric disorders. Methods: This naturalistic, registry-based study used data from the SENTIA cohort, which prospectively monitors antipsychotic safety in individuals under 18 years at a university hospital in Spain. Clinical characteristics were compared between participants with and without ASD. Longitudinal body mass index (BMI) z-score trajectories were analysed using linear mixed-effects models. Results: The sample included 266 participants, of whom 113 (42.5%) had ASD. Individuals with ASD were more often male and initiated antipsychotic treatment at a younger age. Of the 26 participants prescribed an antipsychotic before age 6, 88.5% had ASD. Comorbidity profiles were similar across groups. Risperidone and aripiprazole were the most frequently prescribed antipsychotics. BMI z-scores increased over time (β = 0.130, p = 0.017), and baseline BMI z-score was the strongest predictor. ASD diagnosis did not modify the average linear rate of BMI z-score change (time × ASD: p = 0.251); however, a significant quadratic time × ASD interaction (β = −0.016, p = 0.041) was consistent with a more pronounced early increase followed by earlier attenuation of BMI z-scores in the ASD group. Conclusions: Although antipsychotic treatment was initiated earlier in youth with ASD, no clear difference was observed in the rate of BMI z-score change. Differences in weight trajectories underscore the need for metabolic monitoring in antipsychotic-treated youth.