The effect of docosahexaenoic acid (DHA) supplementation (345 mg/d) on the symptoms of attention deficit/hyperactivity disorder (ADHD) was determined in 63 children, ages 6 to 12 years, at the Mayo Clinic and Baylor College of Medicine, Houston, TX. All were receiving effective therapy with stimulant medication, and were assigned at random, double-blind, to DHA or placebo groups for 4 months. Outcome was determined by scores on laboratory measures of inattention and impulsivity (TOVA, Color Trails), performed after discontinuing medication for 24 hours, and scores on parent rating scales (Child Behavior Checklist, Conners’ Rating Scale), completed while continuing medication. Plasma phospholipid fatty acid patterns were measured at baseline and at the end of the study. Children with ADHD had low levels of plasma DHA at baseline. Differences between DHA and placebo groups, determined by analysis of variance, showed that plasma phospholipid DHA content of the supplemented group was 2.6-fold higher at the end of the study compared to the placebo group. Measures of inattention and impulsivity and parental questionnaires showed no significant improvement in the DHA group. Errors of omission on the TOVA test increased significantly in the DHA group but not in the placebo group, and errors of commission decreased significantly in the placebo group but not in the DHA group. 
COMMENT. A 4-month trial of DHA supplement, administered while continuing effective stimulant medication, had no measurable significant effect on ADHD symptoms observed by the parents. Similarly, objective tests of attentiveness and impulsivity, administered after a 24 hour withdrawal of medication, showed no significant benefit in children receiving DHA supplement. It was assumed that any lasting or withdrawal effect of stimulant medication had dissipated in the short 24 hour drug holiday. The well known “rebound” phenomenon when MPH is discontinued could have vitiated any possible benefit from DHA. [2, 3]
The limitations of this study include the following: 1) trial subjects who were already benefited by stimulant medication; 2) the use of a single dose of DHA supplement; 3) failure to include arachidonic acid and other fatty acids that are often at low levels in children with ADHD. Future controlled studies might be conducted in cases of ADHD previously untreated with stimulant medication, using more than one dose of supplement, and with multiple fatty acids.
Kemper KJ, in an editorial , advocates the testing of further dietary supplements, and greater assurances of safety, purity, and potency before marketing.
For a review of dietary supplements in ADHD, see Progress in Pediatric Neurology III, PNB Publ, 1997;pp209-210. Mitchell EA et al, in 1987, found that DHA and arachidonic acid serum levels were significantly lower in 44 hyperactive children compared to 45 age- and sex-matched controls. Stordy BJ, in 1995, reported that DHA supplements improved dark adaptation (scotopic vision) in 5 adults with dyslexia. She later proposed DHA as a treatment for ADD and short term memory problems.