The Efficacy of Nutritional Interventions in Reducing Childhood/Youth Aggressive and Antisocial Behavior: A Mixed‐Methods Systematic Review and Meta‐Analysis

Aggressive/antisocial behaviors in children and youth may result in impairments in family, social, or academic functioning and lead to long‐term negative consequences for both the individual and society as a whole. The potential of healthy diet and nutritional supplements to reduce aggression and antisocial behavior is an active area of study in nutritional mental health sciences. The goal of this systematic review is to (1) investigate the effectiveness/efficacy of nutritional interventions (dietary manipulation, fortification or supplementation) in reducing excessive aggression, antisocial behaviors, and criminal offending in children/youth (systematic review and meta‐analysis); and (2) provide an overview of implementation barriers and facilitators regarding nutritional interventions in children/youth (qualitative/narrative synthesis). After consulting the Campbell Collaboration's methodological guidelines, a comprehensive search for published and unpublished papers on controlled intervention studies was performed (up to February 26, 2024) using both electronic databases (MEDLINE, Embase, Cochrane Library, APA PsycInfo, Scopus, and the Allied and Complementary Medicine Database) and other resources (e.g., Google Scholar, reference list of included studies and other reviews, websites of public health agencies). This study focuses on children and youth (up to the age of 24) presenting with an above‐average level of aggression/antisocial behavior. In terms of the intervention, we considered both dietary manipulation and nutritional supplementation with a duration long enough (minimum of 1 week) that a significant change in the individual's nutritional status could be expected. We included studies with a controlled design if, for outcomes, they reported on (1) behavioral‐level violence/aggression toward others in real‐life (non‐simulated) settings, (2) antisocial behaviors, or (3) criminal offending. Initial screening, checking for eligibility criteria, data extraction from, and risk of bias assessment for each eligible study were conducted independently by two reviewers. To perform the meta‐analysis, data from each original report were standardized (transformed into Hedges' g) so that results across studies could be meaningfully combined and interpreted. Data conversions, computation of pooled effect sizes, and estimation of publication bias were conducted using the Comprehensive Meta‐analysis software (Version 4). Altogether, 51 reports (describing 50 individual studies) met our inclusion criteria, and 72 effect sizes were extracted from these reports. Nutritional interventions with a broad target (e.g., broad‐spectrum micronutrient supplementation or general improvement in diet quality) had the most consistent and largest intervention benefit across all outcomes (aggression: k = 7, N = 797, g = −0.31, 95% CI = −0.50 to −0.12, p = 0.001; antisocial behavior: k = 13, N = 2109, g = −0.49, 95% CI = −0.73 to −0.24, p