The study, carried out by researchers at the University of Gothenburg in Sweden, surveyed almost 4,000 Swedish males, comparing their intelligence at 15 and again at 18.
Researchers found the intelligence scores of those eating fish once a week were 6% higher on average than those who ate fish less than once a week. The intelligence scores of those who ate fish more than once a week was 11% higher on average.
The study claims to be the first to explore the effect on adolescents, and researchers now plan to explore whether the type of fish consumed has any bearing on the results.
"Between 15 and 18, educational achievements can help to shape the rest of a young man's life," said researcher Kjell Torén.