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Objective: There is growing evidence of involvement of inflammatory mechanisms in ADHD. Previous studies found significantly higher rates of ADHD among children with FMF. The present study examined the rate of exposure to FMF in children with a later (within a 5-year period) diagnosis of ADHD compared to non-ADHD children. Methods: A population-based case-control study of all children (<18 years) registered in Leumit Health Services during 01.01.2006 to 06.30.2021. All cases met ICD-9/10 criteria for ADHD. They were matched by age, sex, and socioeconomic status on a 1:2 rate to randomly selected non-ADHD controls. Results: Fifty-six (0.30%) children with ADHD (N = 18,756) were previously diagnosed with FMF compared to 65 of 37,512 controls (0.17%). A significant, independent association existed between a preceding FMF diagnosis and a later ADHD diagnosis [OR = 1.72 (95% CI 1.18-2.51); p = 0.003]. Conclusions: The mechanisms underlying the association w between FMF and later ADHD diagnosis merit further elucidation.

Objective: We examined the association between the number, magnitude, and frequency of febrile episodes during the 0 to 4 years of life and subsequent diagnosis of ADHD. Methods: This population-based case-control study in an Israeli HMO, Leumit Health Services (LHS), uses a database for all LHS members aged 5 to 18 years between 1/1/2002 and 1/30/2022. The number and magnitude of measured fever episodes during the 0 to 4 years were recorded in individuals with ADHD (N = 18,558) and individually matched non-ADHD controls in a 1:2 ratio (N = 37,116). Results: A significant, independent association was found between the number and magnitude of febrile episodes during the 0 to 4 years and the probability of a later diagnosis of ADHD. Children who never had a measured temperature >37.5°C had a significantly lower rate of ADHD (OR = 0.834, 95% CI [0.802, 0.866], p < 0.0001). Conclusions: Febrile episodes during 0 to 4 years are associated with a significantly increased rate of a later diagnosis of ADHD in a dose-response relationship.