The quality of evidence is downgraded by study limitations (unclear allocation concealment and selective outcome reporting), by inconsistency (unexplained variability in results), and by indirectness (lack of long-term studies).
A Cochrane review [Abstract] 1 included 13 studies with a total of 1 011 subjects. Eight of the included trials had a parallel design: 5 compared an omega-3 PUFA supplement to placebo; 2 compared a combined omega-3 and omega-6 supplement to placebo, and one compared an omega-3 PUFA to a dietary supplement. Five of the included trials had a cross-over design: 2 compared combined omega-3/6 PUFA to placebo; 2 compared omega-6 PUFA with placebo; 1 compared omega-3 to omega-6 PUFA, and one compared omega-6 PUFA to dexamphetamine. Supplements were given for a period of between 4 and 16 weeks.
There was a significantly higher likelihood of improvement in the group receiving omega-3/6 PUFA compared to placebo (RR 2.19, 95% CI 1.04 to 4.62; 2 studies, n=97). However, there were no statistically significant differences in parent-rated ADHD symptoms (SMD -0.17, 95% CI -0.38 to 0.03; 5 studies, n=413); inattention (SMD -0.04, 95% CI -0.29 to 0.21; 6 studies, n=469) or hyperactivity/impulsivity (SMD -0.04, 95% CI -0.25 to 0.16; 5 studies, n=416) when all participants receiving PUFA supplements were compared to those receiving placebo.There were no statistically significant differences in teacher ratings of overall ADHD symptoms (SMD 0.05, 95% CI -0.18 to 0.27; 4 studies, n=324); inattention (SMD 0.26, 95% CI -0.22 to 0.74; 3 studies, n=260) or hyperactivity/impulsivity (SMD 0.10, 95% CI -0.16 to 0.35; 3 studies, n=259).There were also no differences between groups in behaviour, side effects or loss to follow-up.
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