Adolescents with higher levels of an omega-3 fatty acid in their blood may be less likely to develop psychotic disorders in early adulthood, a new study led by the RCSI indicates.

The findings suggest that when it comes to the risk of psychosis, the omega-3 fatty acid may offer a potentially preventative effect.

The study involved over 3,800 people taking part in the Children of the 90s study - an ongoing longitudinal study in the UK. Participants were assessed for psychotic disorder, depressive disorder and generaliaed anxiety disorder at the ages of 17 and 24 years.

During these assessments, blood samples were also collected, and the levels of omega-6 fatty acids, which generally increase inflammation in the body, and omega-3 fatty acids, which generally reduce inflammation, were measured.

The researchers found that while there was little evidence that fatty acids were associated with mental disorders at the age of 17, the 24-year-olds with psychotic disorder, depressive disorder and generalised anxiety disorder had higher levels of omega-6 than omega-3 fatty acids compared to those without these disorders.

They also found that 24-year-olds with psychotic disorder had lower levels of DHA than 24-year-olds without psychotic disorder. DHA is an omega-3 fatty acid typically found in oily fish or dietary supplements.

In a group of over 2,700 people who were monitored over time, adolescents with higher levels of DHA at age 17 were 56% less likely to develop psychotic disorder by the age of 24. This suggests that DHA in adolescence may have a potentially preventative effect when it comes to reducing the risk of psychosis in early adulthood.

The results remained consistent even when other factors were taken into account, such as sex, body mass index and socio-economic status.

“The study needs to be replicated, but if the findings are consistent, these results would suggest that enhanced dietary intake of omega-3 fatty acids among adolescents, such as through oily fish like mackerel, could prevent some people from developing psychosis in their early twenties.

“The results could also raise questions about the relationship between the development of mental health disorders and omega-6 fatty acids, which are typically found in vegetable oils,” explained the study’s senior author, Prof David Cotter, a professor of molecular psychiatry at the RCSI.

According to the study’s first author, PhD student and psychiatry trainee at the RCSI, Dr David Mongan, more research is needed “to learn about the mechanisms behind this effect”.

“It could possibly be related to reducing inflammation or decreasing inappropriate pruning of brain connections during adolescence,” he suggested.

Details of these findings are published in the journal Translational Psychiatry.