Dietary Carbohydrates and ADHD Symptoms: A Systematic Review

Attention-deficit/hyperactivity disorder (ADHD) is a prevalent neurodevelopmental condition with psychosocial impact. Dietary carbohydrates, particularly added sugars, refined starches, and high-glycemic index/load (GI/GL) patterns, have been proposed as modifiable exposures that may relate to attention and behavioral regulation. This systematic review synthesized evidence linking carbohydrate quantity and quality to ADHD-related outcomes.

Following PRISMA 2020, PubMed, Scopus, and Web of Science were searched for English-language studies published from January 2015 to December 2025. Eligible studies included observational and interventional designs in children, adolescents, or adults with a clinical ADHD diagnosis or validated symptom assessment. Risk of bias was assessed using NOS/NOS-adapted criteria, RoB 2, and ROBINS-I. Findings were synthesized narratively by exposure domain.

Of 1174 records identified, 48 studies were included: 38 observational and 10 interventional. Sugar-related exposures showed the most consistent pattern: 15 of 16 studies examining added sugars, sugar-sweetened beverages, sweets, candy, or sweet dietary patterns reported positive associations with ADHD diagnosis, symptom severity, hyperactivity, or less favorable ADHD-related outcomes. Findings for total carbohydrate intake were inconsistent. GI/GL-specific evidence was limited but generally adverse in direction. Among intervention studies, symptom improvement after modification was reported in 6 of 10 studies, whereas 4 studies showed mixed, preliminary, non-significant, or non-superior findings. Most observational studies showed moderate to high risk of bias, while interventional studies showed variable risk across domains.

Poorer carbohydrate quality may be associated with greater ADHD-related symptom burden, whereas total carbohydrate intake showed inconsistent associations. Certainty remains limited by heterogeneity, residual confounding, risk of bias, and limited carbohydrate-specific intervention evidence.