REVIEW OF: Israel A et al, J Atten Disord 2024;28(5):677–685

STUDY TYPE: Population-based case-control study

Some research studies have associated inflammation with ADHD. This new study provides compelling data implicating common childhood fevers as an ADHD risk factor. 

Researchers relied on a comprehensive computerized database to analyze data on 18,558 children with ADHD and 37,116 matched controls without ADHD (ages 5–18). The two groups were matched by age, gender, birth year and quarter, socioeconomic status, ethnicity, and region to prevent variables other than fever from affecting the findings. Data on febrile episodes during the first 4 years of life were collected from medical records, focusing on the number of times (0–3+ measurements) when body temperature exceeded 5 defined fever thresholds (99.5°F [37.5°C] to 103.5°F [39.5°C]).

Kids diagnosed with ADHD had significantly more febrile episodes in their early years than their non-ADHD peers across all temperature thresholds (p<.001). The relationship wasn’t subtle—how often kids had fevers, and how high those fevers ran, correlated with increased ADHD risk. Children who had no documented fevers above 99.5°F actually showed reduced ADHD rates (odds ratio [OR] = 0.834). Kids who had 3+ episodes of fever above 103.5°F had more than double the odds of developing ADHD (OR = 2.135).

CARLAT TAKE
This study found a dose-related correlation between both fever frequency and intensity in early childhood and subsequent ADHD diagnosis, although it is possible that a separate factor drives the risk for both fever and ADHD. Young children are prone to developing fevers from community-acquired infections, from vaccines that can prevent even higher fevers, and even from teething. We would like to see research studying whether fever management can reduce ADHD outcomes. For now, a history of frequent early childhood illnesses might help complete the clinical picture for our patients with ADHD.