CNS Statement on Leucovorin Use in Autism and Related Disorders

Background
In response to recent statements from the U.S. Department of Health and Human Services and the Food and Drug Administration regarding leucovorin use in children with autism spectrum disorder (ASD), the Child Neurology Society (CNS) provides the following guidance to assist clinicians in evidence-based decision-making.

Leucovorin, also known as folinic acid or leucovorin calcium, is a reduced form of folate. It is distinct from the unmetabolized folic acid found in supplements and fortified foods.

Summary of Evidence

• Existing studies examining leucovorin in individuals with ASD are small, methodologically heterogeneous, and in several cases have significant data integrity concerns.
• There is no adequately powered, placebo-controlled, pre-registered clinical trial establishing the efficacy of leucovorin for core autism symptoms [1].
• The only clearly supported indication for leucovorin for neurodevelopmental disorders is for conditions in which folate metabolism is impacted, such as folinic acid-dependent epilepsy, and specific genetic causes of cerebral folate deficiency (CFD), which sometimes manifest as ASD along with other neurological symptoms. In these cases, leucovorin is indicated to address the underlying metabolic problem, rather than the ASD itself.
• Other reported associations, such as folate receptor autoantibody positivity or presumed functional folate deficiency, have not been validated.

Clinical Recommendations

1. Indication

• Leucovorin is primarily indicated for people receiving chemotherapy. 
• Leucovorin may also be used for certain ultra-rare genetically confirmed disorders that are associated with aberrant cerebrospinal fluid (CSF) folate metabolism or transport, such as cerebral folate deficiency or folinic acid-dependent epilepsy.
• It is not indicated for routine use in individuals with autism or other neurodevelopmental disorders.

2. Testing and Diagnostic Workup

• Genetic testing (e.g., exome or genome sequencing) is first-line testing for individuals with autism and would determine if there is a genetically based disorder of cerebral folate metabolism.
• Folate receptor autoantibody testing (FRAT) is not recommended as a basis for clinical decision-making at this time [2].
• Lumbar puncture should not be performed routinely in individuals with autism.

3. Use and Monitoring

• Leucovorin should not be prescribed as standard of care for individuals with autism.
• An ethical framework for considering leucovorin prescriptions in autism outside of CFD should consider both legal guardian discretion, which supports parents/caregivers to request treatment that is not clearly beneficial if it is not clearly harmful, alongside clinician professional judgment, which allows medical professionals to prescribe or decline to prescribe medications for which there is no compelling evidence. [3]
• Optimal dosing and duration of treatment depend on the specific neurological disorder being addressed. There is no established optimal dosing regimen for autism without genetically documented CFD.
• If leucovorin is prescribed for ASD, discuss uncertainties, risks, and ethical considerations, and monitor for both potential benefits and adverse effects with pre-determined metrics. Counsel parents/caregivers about the potential for a high placebo response. Normal developmental maturation may be mistaken for treatment response. 

4. Research Priorities

• Support the development of well-designed trials, culminating in a multicenter randomized controlled trial with preregistered outcome measures.
• Develop validated cell-based assays for folate receptor autoantibodies.

5. Public Health Considerations

• Recognize potential supply limitations and prioritize established indications during shortages and supply chain limitations.

Summary Position

Leucovorin is not a standard or evidence-based therapy for individuals with autism. 

Supplement

[1] Major methodological issues include small sample sizes, lack of blinding, post hoc outcome selection, unverified dosing or formulation errors, and data integrity concerns in key trials. These limitations preclude firm efficacy conclusions. Specifically, there are three small randomized controlled trials (RCT) investigating leucovorin monotherapy as treatment for idiopathic autism. The first showed a large effect size in language improvement.¹ However, as per clinicaltrials.gov, “The study sponsor (UAMS) was unable to completely monitor the study or resolve outstanding queries. The study data cannot be fully validated by the sponsor. The study was placed on Full Clinical Hold by the FDA and terminated by the sponsor as a result of investigator non-compliance.” ² The second study reported a significant improvement in Autism Diagnostic Observation Schedule (ADOS) scores.³ However, this study was small (n=19) and did not adhere to the pre-registered analysis plan. The largest and most recent RCT was retracted due to errors in reported results and concerns about data validity.⁴

[2] The currently available FRAT uses a radioligand assay, a method that may produce a high false-positive rate through nonspecific binding. The gold standard method in neuroimmunology consists of cell-based assays that present the antigen (in this case, the folate receptor) in its membrane-bound conformationally correct format (i.e., how this receptor would appear to immune cells and antibodies that encounter the folate receptor in the brain).⁵  Demonstration of antibodies in serum that bind to antigen presented in a cell-based method is more likely to represent antibody-antigen binding as would be seen in the human condition, as compared to the radioligand assay.

[3] The President’s Commission on Bioethics (1983) emphasized deference to parent/caregiver preferences around treatments with ambiguous benefits,⁶ laying a foundation for the modern ethical framework of the zone of parental discretion, in which parent/caregiver decision-making authority and clinician professional judgment operate within boundaries set by a threshold of harm.^7,8 For practicing child neurologists, this framework emphasizes that clinicians exercise professional judgment to determine if interventions requested by a parent or caregiver meet a threshold of plausibility and safety.

Download Full Statement (PDF)

References

1. Frye, R. E. et al. Folinic acid improves verbal communication in children with autism and language impairment: a randomized double-blind placebo-controlled trial. Mol. Psychiatry 23, 247–256 (2018).
2. https://clinicaltrials.gov/study/NCT01602016?tab=history&a=17  Accessed 19 February 2026
3. Renard, E. et al. Folinic acid improves the score of Autism in the EFFET placebocontrolled randomized trial. Biochimie 173, 57–61 (2020).
4. Panda, P. K. et al. Retraction Note: Efficacy of oral folinic acid supplementation in children with autism spectrum disorder: a randomized double-blind, placebocontrolled trial. Eur. J. Pediatr. 185(2):109 (2026).
5. Sinmaz N, Amatoury M, Merheb V, Ramanathan S, Dale RC, Brilot F. Autoantibodies in movement and psychiatric disorders: updated concepts in detection methods, pathogenicity, and CNS entry. Ann N Y Acad Sci. 2015 Sep;1351:22-38. doi: 10.1111/nyas.12764. Epub 2015 Jun 17. PMID: 26083906.
6. President’s Commission for the Study of Ethical Problems in Medicine and Biomedical and Behavioral Research. Deciding to Forego Life-Sustaining Treatment: A Report on the Ethical, Medical, and Legal Issues in Treatment Decisions. Washington, DC: U.S. Government Printing Office, March 1983. Pages 197-229 (Chapter on Seriously Ill Newborns), especially pp. 217-223.
7. McDougall RJ, Notini L. Overriding parents’ medical decisions for their children: a systematic review of normative literature. J Med Ethics 40:448–452 (2014).
8. Gillam L. The zone of parental discretion: An ethical tool for dealing with disagreement between parents and doctors about medical treatment for a child. Clinical Ethics. 11(1):1-8 (2016).