Association of unprocessed and ultra-processed food consumption and ADHD symptoms: evidence from a Brazilian population-based cohort.

Attention Deficit Hyperactivity Disorder (ADHD) is one of the most prevalent neurodevelopmental disorders during childhood and adolescence. Diet has been identified as a relevant contributor to the worsening of ADHD symptoms in childhood. This study aimed to examine the cumulative impact of consumption of unprocessed and ultra-processed foods at ages 2, 4, and 6-7 on ADHD symptoms at age 6-7, and to identify potential sensitive periods of dietary exposure. We analyzed data from 3643 children enrolled in the 2015 Pelotas (Brazil) Birth Cohort. Negative binomial regression analyses were conducted to evaluate the association between the consumption of unprocessed or minimally processed foods and ultra-processed foods, and to identify potential sensitive periods of exposure. Children who consistently remained in the highest tertile (T3) of unprocessed or minimally processed food consumption across all assessments had, on average, 6.0% lower ADHD symptom scores at 6-7 years of age compared to those who were never in the highest tertile. Conversely, those who belonged to the highest tertile of ultra-processed food consumption twice or at all assessments had, on average, ADHD symptom scores 16.0% and 13.0% higher ADHD symptom scores at 6-7 years, respectively, than children who were never in that tertile. In the analysis of the sensitive periods for food consumption, ultra-processed consumption at ages 4 and 6-7 (IRR: 1.21; 95% CI: 1.07-1.37; p = 0.003) were associated with higher ADHD symptom scores. These findings underscore the importance of establishing healthy dietary intake during childhood and suggest a potential sensitive period of vulnerability in infancy during which nutrition may have a pronounced impact on neurodevelopment.