From the Lancet:

Summary

Background: We undertook a randomised, double-blinded, placebo-controlled, crossover trial to test whether intake of artificial food colour and additives (AFCA) affected childhood behaviour.

Method: 153 3-year-old and 144 8/9-year-old children were included in the study. The challenge drink contained sodium benzoate and one of two AFCA mixes (A or B) or a placebo mix. The main outcome measure was a global hyperactivity aggregate (GHA), based on aggregated z-scores of observed behaviours and ratings by teachers and parents, plus, for 8/9-year-old children, a computerised test of attention. This clinical trial is registered with Current Controlled Trials (registration number ISRCTN74481308). Analysis was per protocol.

Findings: 16 3-year-old children and 14 8/9-year-old children did not complete the study, for reasons unrelated to childhood behaviour. Mix A had a significantly adverse effect compared with placebo in GHA for all 3-year-old children (effect size 0·20 [95% CI 0·01–0·39], p=0·044) but not mix B versus placebo. This result persisted when analysis was restricted to 3-year-old children who consumed more than 85% of juice and had no missing data (0·32 [0·05–0·60], p=0·02). 8/9-year-old children showed a significantly adverse effect when given mix A (0·12 [0·02–0·23], p=0·023) or mix B (0·17 [0·07–0·28], p=0·001) when analysis was restricted to those children consuming at least 85% of drinks with no missing data.

Interpretation: Artificial colours or a sodium benzoate preservative (or both) in the diet result in increased hyperactivity in 3-year-old and 8/9-year-old children in the general population.

Researchers were from:

School of Psychology, Department of Child Health, University of Southampton, Southampton, UK
School of Medicine, Department of Child Health, University of Southampton, Southampton, UK
Department of Paediatrics, Imperial College, London, UK

UPDATE: The above research, showing that food additives can trigger hyperactivity, is consistent with the medical position in the UK in general, which does not recognize ADHD as a disorder. Note that hyperactivity is not the same thing as ADHD—many things can given symptoms that overlap with ADHD, including basic things like dehydration. But if someone truly has ADHD, then eliminating all food additives from the diet will have no effect on the ADHD. If eliminating food additives does make the “ADHD” go away, then the problem wasn’t ADHD in the first place—the person simply had a sensitivity to food additives that caused hyperactive behavior.

From a reader, a quotation from ADDitude magazine:

“Ask the Experts” column:

Q: “I recently moved to England, and I’m having trouble finding a doctor who’s knowledgeable about ADHD. How can I get appropriate care?”

A: Unfortunately, few clinicians in the United Kingdom consider ADHD a treatable neurological disorder. They view symptoms like inattentiveness and hyperactivity as evidence of a behavioral problem.  - Larry Silver, M.D.