Lidy M Pelsser

ADHD as a (non) allergic hypersensitivity disorder: A hypothesis

Research data concerning the causal association between attention deficit hyperactivity disorder (ADHD) and allergies are conflicting. Allergic disorders, like asthma and eczema are clinical syndromes in which both genetic predisposition and environmental factors (pets, pollen and foods) contribute to its development. The hypothesis of ADHD, in some children also being an allergic disorder, is postulated based on comparison of the mechanisms underlying the development of ADHD and allergic disorders. According to the accepted terminology, ADHD may comply with the criteria of hypersensitivity, allergy and atopy. This hypothesis has to be thoroughly tested by randomized controlled trials using environmental triggers and immunologic research. As genes related to the immune system may be associated with ADHD, further genetic research is compulsory. Immunotherapeutic approaches, using immunotherapy and probiotics, can subsequently be implicated in the treatment of ADHD. If hypersensitivity to environmental stimuli like foods contributes to the development of ADHD, the assessment and treatment of ADHD will have to be reconsidered, thereby improving the quality of care for these patients.

A randomised controlled trial into the effects of food on ADHD.

The aim of this study is to assess the efficacy of a restricted elimination diet in reducing symptoms in an unselected group of children with Attention deficit/hyperactivity disorder (ADHD). Dietary studies have already shown evidence of efficacy in selected subgroups. Twenty-seven children (mean age 6.2) who all met the DSM-IV criteria for ADHD, were assigned randomly to either an intervention group (15/27) or a waiting-list control group (12/27). Primary endpoint was the clinical response, i.e. a decrease in the symptom scores by 50% or more, at week 9 based on parent and teacher ratings on the abbreviated ten-item Conners Scale and the ADHD-DSM-IV Rating Scale. The intention-to-treat analysis showed that the number of clinical responders in the intervention group was significantly larger than that in the control group [parent ratings 11/15 (73%) versus 0/12 (0%); teacher ratings, 7/10 (70%) versus 0/7 (0%)]. The Number of ADHD criteria on the ADHD Rating Scale showed an effect size of 2.1 (cohen’s d) and a scale reduction of 69.4%. Comorbid symptoms of oppositional defiant disorder also showed a significantly greater decrease in the intervention group than it did in the control group (cohens’s d 1.1, scale reduction 45.3%). A strictly supervised elimination diet may be a valuable instrument in testing young children with ADHD on whether dietary factors may contribute to the manifestation of the disorder and may have a beneficial effect on the children’s behaviour.

Diet and ADHD, Reviewing the Evidence: A Systematic Review of Meta-Analyses of Double-Blind Placebo-Controlled Trials Evaluating the Efficacy of Diet Interventions on the Behavior of Children with ADHD

Introduction Attention-deficit/hyperactivity disorder (ADHD) is a debilitating mental health problem hampering the child’s development. The underlying causes include both genetic and environmental factors and may differ between individuals. The efficacy of diet treatments in ADHD was recently evaluated in three reviews, reporting divergent and confusing conclusions based on heterogeneous studies and subjects. To address this inconsistency we conducted a systematic review of meta-analyses of double-blind placebo-controlled trials evaluating the effect of diet interventions (elimination and supplementation) on ADHD. Methods Our literature search resulted in 14 meta-analyses, six of which confined to double-blind placebo-controlled trials applying homogeneous diet interventions, i.e. artificial food color (AFC) elimination, a few-foods diet (FFD) and poly-unsaturated fatty acid (PUFA) supplementation. Effect sizes (ES) and Confidence intervals (CI) of study outcomes were depicted in a forest plot. I2 was calculated to assess heterogeneity if necessary and additional random effects subgroup meta-regression was conducted if substantial heterogeneity was present. Results The AFC ESs were 0.44 (95% CI: 0.16–0.72, I2 = 11%) and 0.21 (95% CI: -0.02–0.43, I2 = 68%) [parent ratings], 0.08 (95% CI: -0.07–0.24, I2 = 0%) [teacher ratings] and 0.11 (95% CI: -0.13–0.34, I2 = 12%) [observer ratings]. The FFD ESs were 0.80 (95% CI: 0.41–1.19, I2 = 61%) [parent ratings] and 0.51 (95% CI: -0.02–1.04, I2 = 72%) [other ratings], while the PUFA ESs were 0.17 (95% CI: -0.03–0.38, I2 = 38%) [parent ratings], -0.05 (95% CI: -0.27–0.18, I2 = 0%) [teacher ratings] and 0.16 (95% CI: 0.01–0.31, I2 = 0%) [parent and teacher ratings]. Three meta-analyses (two FFD and one AFC) resulted in high I2 without presenting subgroup results. The FFD meta-analyses provided sufficient data to perform subgroup analyses on intervention type, resulting in a decrease of heterogeneity to 0% (diet design) and 37.8% (challenge design). Conclusion Considering the small average ESs PUFA supplementation is unlikely to provide a tangible contribution to ADHD treatment, while further research is required for AFC elimination before advising this intervention as ADHD treatment. The average FFD ES is substantial, offering treatment opportunities in subgroups of children with ADHD not responding to or too young for medication. Further FFD research should focus on establishing the underlying mechanisms of food (e.g. incrimination of gut microbiota) to simplify the FFD approach in children with ADHD.