Trajectories of autism symptom severity for boys and girls across childhood.

Girls, more than boys, experience a decrease in the severity of autism symptoms during childhood. It is unclear, however, which specific autistic behaviors change more for girls than for boys. Trajectories of autism symptoms were evaluated using the Autism Diagnostic Observation Schedule-calibrated severity scores (ADOS-CSS). Change in the specific behavioral characteristics of autism was assessed by studying individual ADOS items for 183 children (55 girls) from age 3-to-11 years. Girls decreased in total autism symptom severity (ADOS-CSS) and restricted/repetitive behavior severity (RRB-CSS) across childhood, while boys remained stable in both. Girls showed decreasing-severity trajectories for seven ADOS items and an increasing-trajectory for one item. Boys showed decreasing-severity trajectories for six items and increasing-severity trajectories for three items. Girls with higher ADOS-CSS at age 3 were more likely to decrease in total symptom severity than other girls. Girls in our study mostly improved or remained stable in autism symptom severity and its specific behaviors during childhood, especially behaviors related to being socially engaged and responsive. Boys' symptom change was variable over time and included both improvement and worsening, especially in social behaviors that are key to interaction. Girls with high early severity levels can potentially decrease substantially in severity during childhood.Lay AbstractThe severity of overall autism symptoms tend to decrease more in autistic girls than in autistic boys during childhood, but we do not know which specific behaviors drive this difference. We studied how specific behaviors characteristic of autism change for girls and boys across childhood. We found that girls mostly improve or remain stable in the severity level of their autism symptoms and its specific behaviors during childhood. They improved mostly in behaviors related to being socially engaged and responsive to others. Furthermore, we found that it is possible for girls with high early autism symptoms to show major improvement during childhood. Boys improved in some specific behaviors but worsened in others. Boys worsened in some behaviors that are key to engaging in social interactions.