The study found that in a small clinical trial involving boys 8 to 14 years old, parents rated their son's ability to pay attention more highly if the child's diet was supplemented for 16 weeks with the long-chain fatty acid than if he got a placebo instead.
In the study, 40 subjects got an average of 650 mg per day of Docosahexaenoic Acid (DHA) and 650 mg of Eicosapentaenoic acid (EPA), two different kinds of Omega-3s, in margarine. Half the subjects had been diagnosed with ADHD and the other half were normally-developing kids. The subjects who got margarine without the Omega-3 supplement (the placebo group) were also equally divided between those with ADHD and those who had no such diagnosis.
The notable finding was that, whether or not they had ADHD, boys who got the Omega-3 supplement were rated by their parents as more attentive.