The study of nearly 4,000 teenagers, published in the March issue of Acta Paediatrica, found eating fish once a week was enough to increase combined, verbal and visuospatial intelligence scores by an average of 6 percent, while eating fish more than once a week increased them by just under 11 percent.
Swedish researchers compared the responses of 3,972 males who took part in the survey with the cognitive scores recorded in their Swedish Military Conscription records three years later.
"We found a clear link between frequent fish consumption and higher scores when the teenagers ate fish at least once a week" Kjell Toren of the Sahlgrenska Academy at the University of Gothenburg said in a statement. "When they ate fish more than once a week the improvement almost doubled."
The study also found that:
-- 58 percent of the boys who took part in the study ate fish at least once a week and a further 20 percent ate fish more than once a week.
-- When male teenagers ate fish more than once a week their combined intelligence scores were on average 12 percent higher than those who ate fish less than once a week.
-- The verbal intelligence scores for teens who ate fish more than once a week were on average 9 percent higher than those who ate fish less than once a week. Those who ate fish once a week scored 4 percent higher.