Attention-deficit/hyperactivity disorder and odds of subsequent multiple sclerosis: a population-based retrospective case–control study

Impaired attention and executive function are common in both multiple sclerosis (MS) and attention-deficit/hyperactivity disorder (ADHD). This study aimed to assess the association between prior ADHD and subsequent development of MS. A retrospective, population-based case–control study using the Israeli Clalit Health Services database (2002–2024). MS cases were identified using ICD codes and medication dispensations. Each case was matched with ten controls by age, sex, socioeconomic status, and ethnicity. Controls did not have MS at the index date of their matched case. ADHD was defined by ICD codes and medication dispensations. Odds ratios for MS following prior ADHD were estimated using multivariable models adjusted for smoking, autoimmune comorbidities, BMI and vitamin D. The study included 5,074 individuals with MS and 50,633 matched controls. 68% were female, mean age at MS diagnosis was 42.7 ± 15.0 years. Prior ADHD was independently associated with higher odds of MS after adjusting for other risk factors (aOR 2.54, 95% CI = 2.11- 3.1, p < 0.001). This association was observed for both childhood and adult ADHD and was independent of the lag between diagnoses. ADHD is associated with increased odds of subsequent MS. This association may reflect prodromal MS, shared risk factors or an inflammatory response to ADHD-related CNS changes. While routine screening of individuals with ADHD for MS is not warranted, judicious use of MRI may facilitate earlier diagnosis and treatment.