2025 Autism Research Year in Review

Scientific Progress During a Challenging Year

2025 has been a monumentally challenging year for scientists in general and for autism researchers in particular, but despite drastic federal funding cuts, scientists continued to make progress toward understanding autism’s causes, improving diagnosis, and developing more effective treatments and supports for individuals with autism and their families. According to an Autism Science Foundation survey, about $80 million in autism funding was eliminated early this year as part of Department of Government Affairs (DOGE) cuts. This included approximately $80 million in autism research across the NSF, CDC, and NIH. In September, we received some encouraging news when the NIH announced $50 million in funding for 13 projects under the new Autism Data Science Initiative (ADSI), which will utilize U.S. datasets to investigate gene–environment interactions. These studies will examine a range of environmental factors, individually and in combination, and explore their roles in autism prevalence and causation.

Meanwhile, there was substantial progress toward understanding the biology of autism, including new insights into causes and effective supports, and important findings on biological subtyping.

Heterogeneity: Studies Confirm Autism Subtypes

One of the clearest scientific themes of 2025 was progress in understanding the differences of people with autism across the spectrum. Large-scale biological and behavioral analyses published this year identified reproducible subgroups within autism, including groups that differ in genetic backgrounds, biological features, changes in behavioral features over time, and co-occurring medical or behavioral profiles. These studies have the potential to shift the field away from treating autism as a single, uniform condition toward stratified, precision approaches and targeted supports.

Researchers used artificial intelligence paradigms to identify behavioral patterns and group individuals by shared features. They then compared biological characteristics across these groups to identify underlying mechanisms. This work began last year, and the findings reported in 2025 have been among the most impactful to date in defining autism subtypes. Using this approach, one study identified four subtypes, including one that closely aligns with profound autism (“broadly affected”), another characterized by higher rates of psychiatric conditions such as anxiety or ADHD (“moderately affected”), and two groups with milder challenges.1 Another study found that age at diagnosis—early childhood versus adolescence—was the strongest predictor of subtype. Children diagnosed earlier tended to have delays in language, motor skills, and overall development, while those diagnosed later were more likely to have OCD, ADHD, or anxiety.2 Those who are diagnosed later had co-morbid psychiatric issues that may have masked an autism diagnosis.

Genes are early determinants of biology and behavior, making it critical to understand how genetics contributes to these behavioral differences. These studies found that individuals with greater challenges tend to carry larger, rarer genetic variants, whereas those with milder or later-diagnosed autism show a higher burden of smaller, more common variants.1,2 Certain rare variants, known as de novo variants and not inherited from either parent, are associated with more severe autism features.3

Looking beyond genetics to brain structure, additional studies showed that the severity of autism traits measured by the ADOS, both in individuals with autism and in individuals with ADHD, was a primary driver of differences in brain structure, rather than diagnostic category alone.4 The overlap in behavioral features, brain structure, and genetics across autism and many psychiatric disorders highlights the transdiagnostic nature of many neurodevelopmental traits5,4 calling into question existing diagnostic boundaries. Many of the brain changes studied, including differences in cell density, were similar in individuals with ADHD and autism and more dependent on severity of symptoms.4,6 Other studies demonstrated that autism-related brain differences are also present in individuals without an autism diagnosis who nonetheless show elevated autism traits.7 Taken together, these studies confirm that autism is not a single condition. As research progresses, a key priority will be to better understand subgroups within the broader non-profound autism population so that supports and services can be more effectively tailored.

Genetics and Environmental Factors

Individual functioning is influenced not only by genetics but also by environmental factors unique to each individual or family. These include chemical, nutritional, and contextual influences that warrant further study.8 While some environmental factors, like prenatal birth, may affect the probability of an autism diagnosis independent of genetic risk9,10, they may also modify outcomes and capabilities in individuals who are already diagnosed.11,12 Scientists increasingly agree that a broad range of environmental exposures should be studied in relation to developmental outcomes across diagnostic boundaries and along a continuum, rather than focusing narrowly on autism alone.8,13 

This year, studies also helped exonerate environmental factors that are not related to autism, including acetaminophen. In 2025, global health authorities and scientific reviews reaffirmed that there is no proven causal link between Tylenol (acetaminophen) use during pregnancy and autism. Organizations such as the World Health Organization and the American Academy of Pediatrics noted that existing studies show inconsistent associations and do not establish causation. These clarifications came amid political claims suggesting a connection, prompting experts and advocacy groups like ASF to emphasize that autism’s causes are complex and not attributable to anything parents did or did not do before, during, or after pregnancy.14

Sex Differences

Research in 2025 also advanced understanding of sex differences in autism, particularly the biological mechanisms that shape them. Large genomic datasets, built over decades, revealed why females are less frequently diagnosed than males. Females—especially those with cognitive and motor challenges—carry a higher burden of de novo variants than males, despite no difference in the specific genes affected.15 This pattern supports the concept of differential liability, in which females may have greater biological resilience to autism-related risk.

Additional findings suggest that sex differences arise from multiple mechanisms beyond a single female protective effect. Studies showed that female siblings of individuals with autism have language difficulties that are milder than those seen in autism but greater than those in unrelated peers.16 Other work found that although females are typically diagnosed later overall17, among children diagnosed before age two, females outnumber males.18 Females also have higher rates of co-occurring mental health conditions, which may complicate or delay diagnosis.18 These differences may reflect both biological variation and diagnostic bias, which could be addressed through clinician training and refinement of diagnostic instruments.19 For example, Black autistic girls are less likely to receive a diagnosis despite similar social responsiveness scores, underscoring the role of bias in diagnostic practices.20

Other biological mechanisms underlying sex differences involve the X chromosome. Because females have two X chromosomes, understanding X-linked gene expression in both sexes is critical. Research in 2025 identified 33 X-linked variants consistently associated with autism.21 These variants are involved in brain development at different stages and show sex-specific expression patterns.21 Differences between X- and Y-linked genes may further contribute to sex differences in autism presentation and diagnosis.

Moving Toward Precision Medicine

In 2025, multiple studies used organoids and genetic medicines to advance targeted, personalized approaches for autism, particularly in individuals with known genetic conditions. Organoid and assembloid technologies allow scientists to observe early brain development and identify where developmental pathways diverge in autism. Organoids derived from an individual’s own cells can model that person’s unique neurobiology, enabling researchers to test how brain circuits develop and respond to interventions in a highly personalized way. For individuals with autism, this approach may help identify treatments tailored to specific genetic and cellular profiles rather than relying on one-size-fits-all strategies.

Organoids are being used to develop personalized interventions for conditions including FMR1-related disorders, Timothy syndrome, MECP2-related disorders, and Dup15q syndrome.22,23 These studies include efforts to predict responses to anti-seizure medications24 and to better understand early cellular processes that influence autism risk.25 

Similarly, researchers made progress in genetic medicines, with early studies demonstrating the feasibility for autism linked to highly penetrant genetic variants. Approaches using antisense oligonucleotides (ASOs), CRISPR-based tools, and RNA repair strategies have advanced from animal models toward human trials, including clinical studies in Angelman syndrome26 and Rett syndrome.27 These advances are moving the field from gene discovery toward functional recovery.28 Additional progress has brought other potential therapeutics closer to autism-specific trials.28 While gene therapies target specific mutations, treatments developed for one rare genetic condition are now being explored in related conditions and, potentially, in idiopathic autism. Examples include trials of IGF-129,30 and metformin.31 Developing an evidence base for cross-disorder treatments will open the door to further expanding their utility in autism without an established genetic cause.

Predicting the Future Using a Longitudinal Design

Families often wonder how their child with autism will develop throughout their life and how they should prepare.32 Studying individuals over time, rather than at a single age, has revealed important insights into outcomes, including which features are likely to remain stable and which may improve. In general, individuals with lower baseline abilities tend to show more challenging developmental trajectories, although this pattern is not universal.33,34 Environmental factors, such as socioeconomic status, may also influence both baseline abilities and developmental trajectories.33  Cognitive ability was the most predictive of core autism symptom trajectory, indicating it strongly predicts ASD outcomes.   

At a neurobiological level, developmental trajectories may be partially explained by autism-related differences in temporal lobe white matter development. Autistic brains show altered patterns of synaptic pruning during development, which may affect how neural circuits mature over time.35

Research using rare and critical postmortem brain tissue from individuals with autism has begun to show how the autistic brain changes across the lifespan at a cellular level. However, this line of research is severely limited by the scarcity of available brain tissue. Future studies should examine distinct autism subtypes or subgroups—defined by behavioral features or co-occurring conditions—to better understand differences in brain development. Funding agencies should recognize the long-term value of longitudinal and tissue-based research and support sustained staffing, participant engagement, and the evolving needs of families followed over time.32

Early Intervention Promotes Improvement

This year, scientists compiled large datasets to study predictors of early intervention outcomes. These studies examined a range of intervention modalities targeting core autism features. Researchers found that intervention effectiveness is influenced by factors such as duration and intensity,36,37 baseline skill levels at the start of intervention,36–38 and earlier age at entry,37,38 but not by the specific name or branded model of the intervention. In other words, interventions with different names that focus on skill learning and the promotion of social and cognitive development were broadly beneficial. 

By contrast, duration, intensity, and earlier age at entry were consistently associated with improvements in cognitive and language abilities.36,37 Because young children receive much of their social interaction from parents or other caregivers, parent involvement has proven to be a critical component of effective early intervention.39 These approaches are now being applied successfully to infants who show early signs of developmental challenges, extending intervention efforts to even earlier stages of development.40

Managing Severe, Intense, and Dangerous Behaviors

Meaningful progress was also made this year in understanding severe, intense, and dangerous behaviors in autism. This included improved understanding of wandering, a behavior associated with increased risk of injury and death, and more common among autistic children than their non-autistic peers (DiGiuseppi), as well as the development of more effective interventions to reduce wandering (Scheithauer).

This year also saw increased research attention to catatonia, a potentially fatal condition that is more prevalent among individuals with autism and intellectual and developmental disabilities, yet often more difficult to recognize in autistic individuals than in those without an autism diagnosis (Smith). Cases of documented catatonia occur in about 10% of people with autism, although this might be an underestimation due to communication difficulties in individuals with autism, or changes in development over time that may be mistaken for a core autism feature. You will be hearing more about this issue from ASF in the future.

Conclusion

Despite political hostility and the spread of misinformation that disrupted some lines of research, autism scientists rose to the occasion in 2025. They shared discoveries that help families better understand the biological diversity of autism and the nature of different autism subtypes. These findings illustrate both the neurobiology underlying distinct forms of autism and the role environmental factors play in shaping outcomes. Research in 2025 also highlighted both the overlap and the unique features of autism compared with other neurodevelopmental conditions, such as ADHD. Together, these advances move the field closer to ensuring that the right person receives the right treatment at the right time.

References

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