Converging Representations of Attention-Deficit/Hyperactivity Disorder and Autism on Social Media: Linguistic and Topic Analysis of Trends in Reddit Data

Background: Social media platformshave witnessed a substantial increase in mental health-related discussions, with particular attention focused on attention-deficit/hyperactivity disorder (ADHD) and autism. This heightened interest coincides with growing neurodiversity advocacy. The impact of these changes in the conceptualization of ADHD and autism, and the relationship between the 2 conditions, remains underexplored. Objective: We aim to characterize and understand how the relationship between ADHD and autism has evolved in public discourse over the past decade and explore reasons for their growing alignment. Methods: Using Reddit data from 2012 to 2022, we investigated the frequency of ADHD mentions in r/autism and autism mentions in r/ADHD, compared to commonly mentioned conditions. We analyzed user overlap between the 2 subreddits to track cross-subreddit discussions. Following this, we assessed changes in semantic similarity between ADHD and autism using Word2Vecembedding models, alongside commonly mentioned conditions. Finally, thematic changes in subreddit discussions were explored using BERT-based topic modeling across 2 time periods. Results: Our analysis revealed that ADHD and autism have become progressively more associated across these multiple dimensions. In r/ADHD, there was a steep rise in the proportion of posts mentioning "autism" in 2021, overtaking "bipolar" and "OCD" (obsessive-compulsive disorder) to become the most frequently mentioned condition. Similarly, ADHD mentions increased steadily in r/autism, whilethefrequency of posts mentioning "OCD," "PTSD" (posttraumatic stress disorder), and "bipolar" remained stable and low. User overlap between these subreddits grew substantially beginning in 2020. Semantic analysis showed ADHD and autism becoming more closely related from 2019 onward, compared to other conditions. Last, topic modeling indicated growing thematic convergence in ADHD-and autism-related discussions, which reflected an increasing shared emphasis on the experiencesofadults with ADHDand autism, challengesinaccessingdiagnostic assessments,and interpersonal difficulties. Conclusions:Our study clarifieshow discourse around these 2 conditions has converged during a period when they have both attracted rising public attention. These findings contribute to wider discussions about the impacts of rising public interest in mental health concepts. They illustrate that public understandings of relationships between conditions are dynamic and changing in ways that diverge from diagnostic frameworks. Future research should continue investigating changing mental health conceptualizations on social media, as these dynamics are becoming increasingly important for the future of psychiatric practice.