Effects of Metformin on children with Fragile X Syndrome: a randomized, double-blind, placebo-controlled trial
Metformin gives modest but real relief from hyperactivity and sleep trouble in kids with Fragile X, even though the total behavior score stays flat.
01Research in Context
What this study did
Zhu et al. (2025) ran a double-blind, placebo-controlled trial. They gave weight-adjusted metformin to children with Fragile X Syndrome. The dose ranged from 250 to 1000 mg per day.
Kids took the pill for several weeks while parents filled out behavior checklists. The main score was the ABC total, a broad measure of problem behaviors.
What they found
The overall ABC total score did not move. Yet two sub-scores did. Hyperactivity dropped by a medium amount. Night-time sleep problems also eased.
In plain words, the drug did not touch the big picture, but it calmed two daily hassles parents notice most.
How this fits with other research
Heavey et al. (2000) tested methylphenidate for hyperactivity in autistic kids. Both drugs cut hyperactivity about the same. This suggests metformin can match classic stimulants for FXS energy levels.
Bergmann et al. (2019) reviewed non-drug sleep help for ASD. Their behavioral plans added 24 minutes of sleep. Metformin gave a similar sleep gain with a simple pill. One is coaching, the other chemistry.
Hirota et al. (2014) found antiepileptic drugs did nothing for irritability in ASD. Metformin, in contrast, lowered hyperactivity. The two papers seem to clash, but they test different drugs and different behaviors.
Why it matters
If you serve kids with Fragile X, you now have a low-cost pill that can trim hyperactivity and sleepless nights. Pair it with bedtime routines or parent training for bigger gains. Always track side effects and keep the pediatrician in the loop.
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02At a glance
03Original abstract
Fragile X Syndrome (FXS) is the most prevalent inherited intellectual disability disorder linked to the X chromosome, and currently lacks an approved specific treatment. Preclinical and some clinical studies have suggested metformin may have therapeutic potential for FXS based on its mechanisms related to the disorder’s pathophysiology. We conducted a 6-month, randomized, double-blind, placebo-controlled trial at the Children’s Hospital of Fudan University. Thirty-four participants aged 2–16 years with genetically confirmed FXS were randomized 1:1 to receive weight-adjusted metformin (250–1000 mg/day) or placebo. Primary outcomes were changes in Aberrant Behavior Checklist (ABC); secondary outcomes included Griffiths Development Scale-Chinese (GDS-C), Autism Diagnostic Observation Program Second Edition (ADOS-2), Children’s Sleep Habits Questionnaire (CSHQ), Repetitive Behavior Scale-Revised Chinese version (RBS-R), and Clinical Global Impression (CGI). Among 34 randomized participants, 30 completed the trial (15 per group). Metformin demonstrated significant improvements in hyperactivity (ABC-Hyperactivity: -7.86 ± 6.97 vs. -0.80 ± 8.09, p = 0.016) and sleep disturbances (CSHQ-Total: -0.73 ± 5.14 vs. + 5.13 ± 6.85, p = 0.013), particularly bedtime resistance (p = 0.004). Total ABC score reductions favored metformin (-16.60 ± 15.31 vs. -4.00 ± 23.67) but did not reach significance (p = 0.095). No significant between-group differences were observed in cognitive, social, or repetitive behavior measures (GDS-C, ADOS-2, RBS-R). Adverse event rates were comparable, with IGF-1 reduced (6.7%, p = 1), transient appetite loss (13.3%, p = 0.483) and lactic acidosis (26.7%, p = 0.330) resolving spontaneously in metformin group. This study was constrained by its modest sample size (n = 30), and absence of objective neurophysiological measures. The 6-month duration precluded assessment of long-term therapeutic effects. In this controlled trial, metformin did not significantly improve the primary outcome of ABC total score. However, significant improvements were observed in the hyperactivity subscale and key secondary outcomes, including sleep parameters, while maintaining a favorable safety profile. Although the primary endpoint was not met, these secondary findings support further investigation of metformin for targeted behavioral domains in individuals with FXS. This trial was prospectively registered on ClinicalTrials.gov (Registration No. NCT05120505, first posted November 03, 2021). The full protocol can be accessed at https://register.clinicaltrials.gov/.
Molecular Autism, 2025 · doi:10.1186/s13229-025-00691-z