Navigating Shifts in Autism Epidemiology and Off-Label Prescribing: Insights for Healthcare Providers

The clinical landscape of autism spectrum disorder (ASD) is undergoing a profound dual transformation. On one front, long-standing epidemiological assumptions regarding sex ratios and diagnostic timing are being dismantled by large-scale population studies. On another front, clinical practice faces abrupt shifts in prescribing patterns driven by public media reports, executive statements, and non-FDA-approved off-label drug promotion.

Recent Research

Two 2026 studies published in top-tier medical journals, BMJ and JAMA Network Open, provide essential empirical data that illuminate these changing paradigms. The first study, a 35-year population-based birth cohort study by Fyfe et al. (2026) involving over 2.75 million individuals in Sweden, reveals that the historical male-to-female ratio (MFR) in autism incidence has dramatically declined, driven by an adolescent and young-adult female “catch-up” effect. The second study, an electronic health record cohort study of over 838,000 pediatric patients with ASD across the United States by Rothman et al. (2026), highlights a >24-fold spike in off-label leucovorin (folinic acid) prescribing following media broadcasts and White House press announcements. Together, these studies demand a clinical re-evaluation of how providers screen, diagnose, and deliver evidence-based care to autistic patients across the lifespan.

Why It Matters

Paradigm Shifts in Epidemiology and Prescribing Influences

For decades, autism spectrum disorder was conceptualized primarily as a male-dominated neurodevelopmental condition, with classical teaching citing a male-to-female diagnostic ratio between 3:1 and 4:1. Traditional theories—including the “female protective effect” (requiring a higher genetic mutation load in females for clinical expression), the “greater male variability” hypothesis, and the “extreme male brain” framework- were anchored in observational data that heavily relied on early childhood clinical ascertainment.

Dismantling the Sex-Ratio Dogma

The findings from Fyfe et al. fundamentally challenge these classical models. By evaluating a complete population cohort of 2,756,779 liveborn children in Sweden followed up to 37 years (follow-up 1987–2022), the researchers observed a 10-fold increase in ASD incidence rates over two decades (e.g., rising among 10-to-14-year-olds from 56.5 to 564.1 per 100,000 person-years between 2000 and 2022). Crucially, while the MFR remained stable at around 3:1 for children under age 10, it dropped below 1.0 for individuals diagnosed after age 15 in recent calendar periods.

By 2022, the cumulative male-to-female ratio (cMFR) by age 20 fell to 1.2, and projections reached parity (1.0) by 2024. This demonstrates that autism is not inherently male-skewed across the lifespan; rather, females experience substantial diagnostic delays.

Media, Politics, and Off-Label Prescription Spikes

Simultaneously, the study by Rothman et al. highlights the susceptibility of pediatric neurodevelopmental prescribing to external public commentary. Using the nationwide Epic Cosmos database representing over 300 million patients, the researchers analyzed leucovorin (folinic acid) prescribing among 838,801 unique pediatric patients with ASD contributing 11.9 million outpatient encounters. Leucovorin, a reduced form of folic acid, has small-trial preliminary data suggesting possible benefit in a subset of folate-deficient or cerebral folate receptor autoantibody-positive autistic children with speech deficits, but lacks large-scale randomized trial evidence for general ASD.

Following a February 2025 CBS Evening News segment and a September 2025 White House announcement promoting leucovorin for autism, prescription rates among children with ASD surged from a baseline mean of 34.1 per 100,000 encounters to 835.4 in November 2025, a 24.5-fold increase. Although the FDA subsequently approved leucovorin in March 2026 for cerebral folate transport deficiency caused by confirmed FOLR1 gene mutations, it explicitly did not approve the drug for general ASD. This rapid surge illustrates how media coverage can drive off-label prescribing ahead of formal evidence and regulatory guidelines.

Who It Affects

Dissecting Clinical Demographics and At-Risk Cohorts

Both studies provide detailed demographic insights that define the specific patient populations impacted by diagnostic delays and changing prescribing trends.

The Delayed Female Autistic Population

In the Swedish birth cohort (N = 2,756,779), a total of 78,522 individuals received an ASD diagnosis by 2022. The peak age of diagnosis differed significantly by sex: males peaked at ages 10–14 years (645.5 per 100,000 person-years in 2020–2022), whereas females peaked at ages 15–19 years (602.6 per 100,000 person-years).

The female “catch-up” phenomenon is driven by multiple clinical mechanisms:

• Social Camouflaging and Masking: Autistic girls frequently exhibit stronger superficial social communication skills and mimic peer behaviors during early childhood, effectively masking core traits until adolescent social environments exceed their compensatory strategies.
• Diagnostic Overshadowing: Females are significantly more likely than males to receive preceding psychiatric diagnoses, such as anxiety, depression, eating disorders, or obsessive-compulsive disorder—before their underlying autism is identified. Diagnostic overshadowing often leads clinicians to misattribute autistic traits to internalizing psychiatric conditions.
• Diagnostic Tool Sex Bias: Early screening and assessment instruments were standardized predominantly on male cohorts, emphasizing overt behavioral disruptions over internalizing, socially monitored presentations typical of females.

What Doctors Should Know About Autism “Unmasking” in Girls

A significant paradigm shift is taking place in developmental pediatrics and child psychiatry. Historically, autism spectrum disorder (ASD) was viewed as a predominantly male condition, with classic teaching emphasizing a 4:1 male-to-female diagnostic ratio in childhood. However, recent epidemiological research—including a large-scale BMJ study demonstrating that the male-to-female diagnosis ratio equalizes to 1:1 by age 20—reveals that girls and young women have not been inherently less autistic, but rather significantly underidentified and diagnosed much later in life.

Central to this changing landscape is the phenomenon of autistic masking and the growing movement toward “unmasking.” For healthcare providers, recognizing how masking presents and how unmasking unfolds is becoming essential for delivering timely, accurate, and supportive care.

Understanding Masking and the “Unmasking” Movement

Autistic masking (or camouflaging) refers to the conscious or unconscious suppression of natural autistic traits to blend into neurotypical social environments. Autistic girls and young women are particularly adept at masking. From an early age, they often mimic peer speech patterns, force eye contact, suppress stimming behaviors, and meticulously study social dynamics to avoid standing out.

While masking can temporarily allow an individual to pass as neurotypical, it carries a severe psychological toll. Chronic camouflaging frequently leads to intense mental exhaustion, identity confusion, heightened anxiety, and eventual autistic burnout.

In recent years, a cultural shift fueled by social media awareness and public figures speaking openly about neurodiversity has encouraged young women to drop these protective strategies, a process known as unmasking. As patients begin to unmask, previously hidden autistic traits often surface for the first time, prompting teen girls and young women to seek clinical evaluation.

Key Clinical Insights for Healthcare Providers

1. Differentiating Autism from Co-occurring Conditions

Because masked autistic traits are difficult to identify early on, girls frequently enter the healthcare system through secondary presentations. Clinicians often observe prior or co-occurring diagnoses of anxiety, depression, eating disorders, or attention-deficit/hyperactivity disorder (ADHD). Recognizing whether these presentations are secondary to the exhaustion of autistic masking—rather than isolated primary psychiatric disorders—is crucial for selecting appropriate interventions.

2. Assessing Stress and Burnout Levels

Unmasking is rarely a simple, linear process. When patients drop their masking strategies, clinicians may observe a temporary increase in emotional distress, sensory overload, or behavioral changes as hidden exhaustion comes to light. Providers should carefully evaluate patient stress levels and environmental demands, ensuring that unmasking occurs in a safe, supportive environment rather than leading to overwhelming burnout.

3. Adapting Diagnostic Approaches

Traditional diagnostic tools and screening instruments were largely standardized on young male cohorts, emphasizing externalizing behaviors and overt social deficits. To accurately evaluate girls and young women, clinicians must look beyond superficial social skills and ask directly about the internal effort required to navigate social interactions, sensory sensitivities, and intense, focused interests.

Moving Forward

The rise of the autism “unmasking” movement offers a vital opportunity for healthcare providers to close the longstanding gender gap in autism diagnoses. By understanding the mechanisms of masking, assessing the toll of chronic camouflaging, and differentiating autism from overlapping conditions, clinicians can ensure that autistic girls receive timely validation, accurate diagnoses, and tailored support.

Demographics of Pediatric Leucovorin Recipients

In the US cohort (N = 838,801 patients with ASD), 10,297 unique patients received 23,210 leucovorin prescriptions. Analysis of encounter data reveals specific age and sex distributions among recipients:

Children aged 5 to 11 years accounted for over half (52.8%) of all leucovorin prescriptions, followed by children aged 3 to 4 years (22.9%), reflecting intense caregiver interest during early speech development windows.

What Changes

Guidance for Practice, Prescribing, and Clinical Systems

These findings require immediate adjustments across primary care pediatrics, child psychiatry, and developmental medicine.

Reframing Screening and Diagnostic Protocols

1. Abandon Gendered Pretest Probabilities: Clinicians must eliminate the assumption that autism is predominantly a male condition. Adolescent girls presenting with social anxiety, mood dysregulation, school refusal, or eating disorders should be systematically evaluated for underlying autistic neurodivergence.
2. Re-evaluate Prior Psychiatric Diagnoses: Given the high rates of diagnostic overshadowing in females, clinicians should review complex adolescent psychiatric cases where standard interventions have yielded poor responses, considering unaddressed ASD.
3. Develop Sex-Sensitive Diagnostic Tools: Healthcare systems must adopt updated assessment tools that capture subtle social camouflaging and internalizing presentations.

Rational Guidance on Off-Label Leucovorin Prescribing

1. Adhere to Regulatory Indications: Clinicians must recognize that the FDA approved leucovorin in March 2026 specifically for cerebral folate transport deficiency due to confirmed FOLR1 genetic variants, not for unselected ASD.
2. Institute Targeted Diagnostic Workups: Rather than empirical prescribing driven by media reports, clinicians should restrict leucovorin use to patients with documented metabolic or genetic indications (e.g., confirmed FOLR1 gene variants or verified cerebral folate deficiency via lumbar puncture/autoantibody testing).
3. Transparent Caregiver Communication: Providers should counsel families on the distinction between preliminary trial data and confirmed efficacy, manage expectations regarding speech outcomes, and emphasize established behavioral and speech-language therapies.

Conclusion

The convergence of these epidemiological and pharmacological analyses signals a new era in autism care. Recognizing that lifetime autism incidence reaches sex parity requires a fundamental overhaul of diagnostic frameworks to eliminate late female diagnoses. Simultaneously, navigating rapid shifts in off-label prescribing requires clinicians to remain grounded in objective clinical trial evidence, rigorous genetic/metabolic diagnostic testing, and ethical communication.

References

1. Fyfe C, Winell H, Dougherty J, Gutmann DH, Kolevzon A, Marrus N, Tedroff K, Turner TN, Weiss LA, Yip BHK, Yin W, Sandin S. Time trends in the male to female ratio for autism incidence: population based, prospectively collected, birth cohort study. BMJ. 2026;392:e084164. doi:10.1136/bmj-2025-084164
2. Rothman JM, Kwan B, Longhurst CA, Jena AB. Rates of leucovorin prescriptions for children with autism. JAMA Netw Open. 2026;9(5):e2613286. doi:10.1001/jamanetworkopen.2026.13286