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.
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 ( = 18,558) and individually matched non-ADHD controls in a 1:2 ratio ( = 37,116).
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],  < .0001).
Febrile episodes during 0 to 4 years are associated with a significantly increased rate of a later diagnosis of ADHD in a doseresponse relationship.