Bill Ahearn, PhD, BCBA-D, LABA, Director of Research

July of 2023, the Research Newsletter covered prevalence estimates from the Centers for Disease Control and Prevention (CDC; Maenner et al., 2023) from its Autism and Developmental Disabilities Monitoring network (ADDM) project. Autism prevalence was estimated to have increased to 1 in 36 children at the age of 8. The newest prevalence estimates have been released (CDC; Shaw et al., 2025), and autism prevalence was estimated to increase to 1 in 31 children at the age of 8. So, the trend of increased prevalence has continued. Another recently published study has suggested that autism spectrum disorder can be divided into four subcategories (Litman et al., 2025). This interesting study analyzed data from SPARK. SPARK is an autism research project, funded by the Simons Foundation, aimed at advancing our understanding of the disorder. SPARK has over 150,000 people diagnosed as autistic, as well as over 380,000 first-degree family members, many of whom have shared genetic material.

The Litman et al. (2025) study analyzed data from over 5,300 children in the SPARK database. The data included genetic samples and information gathered from several questionnaire-based assessments (i.e., Social Communication Questionnaire-Lifetime, Repetitive Behavior Scale-Revised, and the Child Behavior Checklist). The questionnaires allow for the identification of the presentation of 239 surveyed items (e.g., challenging behavior, communication skills, social behavior) along with the genetic samples. The results of this research propose that there are distinct characteristics of the individual that correspond to specific patterns of genetic variations. This leads to the suggestion of four subtypes of autism, which are referred to as Autism with:

• Social and Behavioral Challenges, which presents with social behavioral differences and repetitive behavior, but developmental milestones are similar to those in typically developing children. This is the largest group, 37% of the sample, and often co-occurs with ADHD, anxiety, depression, and/ or obsessive-compulsive disorder.

• Mixed ASD with Developmental Delay, which presents with delays in meeting developmental milestones, along with core autism symptoms, but does not co-occur with anxiety, depression, or disruptive behavior. This group was about 19% of the studied sample.

• Moderate Challenges, which presents with milder core autism symptoms, usually reach developmental milestones at expected ages but also do not co-occur with psychiatric disorders. This is the second largest percentage of the sample at 34%.

• Broadly Affected, which presents with more profoundly impacting core symptoms and co-occurring psychiatric conditions. This is the smallest percentage of the sample at around 10%.

The authors stated that they expected “the differences in phenotypes, co-occurring diagnoses and developmental milestones across the four autism classes would correspond to class-specific patterns in genetic signals for common variants.” When examining the genetic presentations of those in these categories, various potential mechanisms were suggested. For example, the most profoundly impaired individuals, the Broadly Affected group, were found to have the most unique genetic mutations (“de novo” mutations) that were not present in their parents. The other group noted to show developmental delays, the Mixed ASD with Developmental Delay group was more likely to have inherited rare genetic variations from their parents. So, although both groups present with developmental delays, the genetic mechanisms involved were different. More research is certainly warranted, but these findings suggest subtypes of the disorder may provide different avenues to diagnosing autism and may have treatment implications.

One well-developed line of research, conducted by behavioral researchers, has suggested that there are subtypes of self-injurious behavior (e.g., head banging or otherwise hitting oneself) when self-injury does not have a clear cause. Examples of clear causes of self-injury include when self-injury produces caregiver attention, access to preferred events, or provides escape or avoidance of aversive events. The work by Hagopian and colleagues (2015/2017) has shown that when self-injury does not have a clear social cause and there are clear differences between test and control conditions, then this type of self-injury responds to alternative sources of reinforcement in the environment. These types of treatments are not overly resource intensive. However, if self-injury does not show these clear differences during assessment, then alternative sources of reinforcement alone are rarely effective in intervention. In these cases, additional treatment components are needed, and the treatment requires intensive resources to implement.

Hagopian, L. P., Rooker, G. W., & Zarcone, J. R. (2015). Delineating subtypes of self-injurious behavior maintained by automatic reinforcement. Journal of Applied Behavior Analysis, 48(3), 523–543. https://doi.org/10.1002/jaba.236

Hagopian, L. P., Rooker, G. W., Zarcone, J. R., Bonner, A. C., & Arevalo, A. R. (2017). Further analysis of subtypes of automatically reinforced SIB: A replication and quantitative analysis of published datasets. Journal of Applied Behavior Analysis, 50(1), 48–66. https:// doi.org/10.1002/jaba.368

Litman, A., Sauerwald, N., Green Snyder, L. et al. (2025). Decomposition of phenotypic heterogeneity in autism reveals underlying genetic programs. Nature Genetics, 57, 1611–1619. https://doi.org/10.1038/s41588-025-02224-z

Maenner MJ, Warren Z, Williams AR, et al. (2023). Prevalence and Characteristics of Autism Spectrum Disorder Among Children Aged 8 Years — Autism and Developmental Disabilities Monitoring Network, 11 Sites, United States, 2020. MMWR Surveillance Summary, 72(No. SS-2):1–14. DOI: http://dx.doi.org/10.15585/mmwr.ss7202a1

Shaw KA, Williams S, Patrick ME, et al. (2025). Prevalence and Early Identification of Autism Spectrum Disorder Among Children Aged 4 and 8 Years — Autism and Developmental Disabilities Monitoring Network, 16 Sites, United States, 2022. MMWR Surveillance Summary, 74(No. SS-2):1–22. DOI: http://dx.doi.org/10.15585/mmwr.ss7402a1

This article originally appeared in the Summer 2025 edition of NECC’s bi-annual publication, Research News.