Childhood Fish Consumption Linked to Higher ADHD.

Studies in recent years have touted the importance of fish consumption for brain development, while also warning of the effects of the neurotoxin mercury in some fish varieties.

Now, a Cape Cod-based study by School of Public Health researchers suggests that higher levels of fish consumption in childhood are associated with elevated odds of attention deficit hyperactivity disorder (ADHD), raising new questions about the benefits and risks associated with fish intake.

The study, in the International Journal of Environmental Research and Public Health, was based on questionnaires completed by more than 1,100 Cape Cod adults who were asked about their fish consumption in childhood (ages 7 to 12) and learning and behavioral problems. Fish intake was not associated with low educational attainment or cognitive or behavioral problems, with the exception of ADHD, the study found.

Participants who reported eating fish several times a week as children had 4.5 times the odds of ADHD as non-fish consumers. They also were more likely to report having difficulty paying attention or sitting still.

“The ADD/ADHD association was strongest for typical consumers of high-mercury fish, but, unexpectedly, also observed for those who typically chose low-mercury fish or canned tuna,” the authors said.

Lead author Ann Aschengrau, professor of epidemiology, said that the low-mercury fish varieties reported by participants were typically also low in n-3 PUFA, a beneficial fatty acid, and therefore would not be expected to yield cognitive benefits. But she added, “It is unclear why typical consumption of relatively low-mercury fish would adversely impact learning abilities and behavioral disorders. Perhaps, the occasional consumption of high-mercury fish had an adverse impact.”

Prior studies have found that children of women who regularly consumed fish (especially low-mercury varieties) during pregnancy tended to score higher on developmental tests, relative to those whose mothers consumed little or no fish. Other studies have shown an association between prenatal mercury exposure and ADHD symptomatology.

The research team said the association between childhood fish intake and ADHD should be further explored in a present-day population of children in order to ensure that reports of fish consumption are as accurate as possible.

Fish consumption in Cape Cod was higher than in the US generally, with 90 percent of study participants reporting some childhood intake, compared to about 50 percent of the general population.

The US Food and Drug Administration and the Environmental Protection Agency recommend that pregnant and breastfeeding women, those who might become pregnant, and young children should eat low-mercury fish in order to gain developmental and health benefits. They recommend that pregnant women eat at least 8 ounces and up to 12 ounces (2‐3 servings) per week of low-mercury fish, such as shrimp, cod, and salmon, while avoiding high-mercury varieties.

Co-authors on the study include: Jenny Carwile, a former postdoctoral associate in epidemiology; Lindsey Butler, a doctoral student in environmental health; Patricia Janulewicz, assistant professor of environmental health; and Michael Winter, associate director of the Data Coordinating Center. The research—an offshoot of a long-running study of contaminated drinking water led by Aschengrau—was funded by a Superfund Research Program grant.

—Lisa Chedekel