The FDA approves leucovorin for the treatment of cerebral folate deficiency (CFD), a rare brain disorder that causes developmental delays and autism-like symptoms such as problems with social communication, sensory processing and repetitive behaviors. The move backs away from officials' earlier push for its use in many children with autism. Leukovorin is a form of vitamin B9 that helps deliver folate directly to the brain. The FDA analyzed the literature from 2009-2024, including case reports, and concluded that leucovorin helps patients with CFD. Studies show improvement in verbal communication and behavior in some children with autism, for example a randomized trial of 48 children showed greater improvement compared to placebo after 12 weeks. A systematic review of 21 studies confirmed improvements in communication, attention and stereotypic behavior with medium to large effects. Evidence for autism treatment is lacking, outcomes vary, and data on long-term safety and standardized dosing are lacking. The American Academy of Pediatrics emphasizes that leucovorin is not a one-size-fits-all treatment for autism.