New research suggests that a readily-available antibiotic can bring about improvements in behavior and anxiety for those with the most common cause of inherited intellectual disability.

In a small study published this week, researchers found “modest” but meaningful gains in those with fragile X syndrome taking the drug minocycline as compared to a placebo.

The finding is significant, researchers say, because the medication — which is commonly used to treat severe acne — is currently available by prescription.

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For the study, 66 children with fragile X ages 3 to 16 were divided into two groups, one receiving minocycline and the other group given a placebo. After three months, the groups switched treatments. All the while, both parents and doctors were not aware who was receiving the real drug versus the placebo.

Ultimately, parents indicated that their children had less anxiety and fewer mood-related behaviors while they were taking the antibiotic, according to the study published in the Journal of Developmental and Behavioral Pediatrics. Assessments from the children’s doctors also showed overall improvement while the kids were taking the drug.

Nonetheless, the study found that some children with fragile X responded better than others to the drug, so researchers are now looking to uncover biomarkers which might help identify who the best candidates for the treatment are.

“This study provides evidence of the efficacy of this medication as a targeted treatment for fragile X syndrome with a long history of use and that can currently be prescribed,” said Mary Jacena Leigh of the University of California, Davis MIND Institute who led the study. “Further studies examining the long-term benefits and side effects are needed, perhaps in combination with other educational and medication treatments currently being developed for individuals with the condition.”