Plasma polyunsaturated fatty acids and mental disorders in adolescence and early adulthood: cross-sectional and longitudinal associations in a general population cohort

The Publication

Polyunsaturated fatty acids (PUFAs) include the omega-6 fatty acids: linoleic acid and arachidonic acid, which have proinflammatory effects, and omega 3-fatty acids, including alpha-linolenic, eicosapentaenoic and docosahexaenoic acids, which are generally anti-inflammatory. We have evolved with a balanced ratio of omega 6: omega 3.  However the modern Western diet has shifted the balance strongly in favour of pro-inflammatory omega 6s. This change in balance is thought to be a driver of many conditions characterised by inflammation, such as cardiovascular and neurodegenerative diseases. There is increasingly more evidence that shows low-grade inflammation could also be contributing to development of mental disorders, such as depression and schizophrenia. Whilst the precise mechanism underpinning why this occurs is unknown, some theories suggest: modulation of HPA axis, neurotransmission, neurodegeneration, and microglial activity.

In addition to inflammation, PUFAs could play alternative roles in neurodegeneration.

This study examined cross sectional and longitudinal associations between PUFAs and mental disorders in a large cohort of young people, providing blood samples at age 17 and 24 years. Such measures were assessed against psychotic disorder, moderate/severe depression and generalised anxiety disorder.

Whilst there was little association between PUFAs and mental disorders at age 17, by the age of 24, the omega 6/omega 3 ratio was positively associated with psychotic disorder, depressive disorder and GAD, whilst DHA was inversely associated with psychotic disorder. In longitudinal analysis, there was evidence of an inverse association between DHA and psychotic disorder at age 17 and at age 24.

Our Response

These findings add more evidence which suggests there is an association between levels of PUFAs and mental disorders. However, this finding shows that a particular focus should be given to DHA to prevent development of psychosis in adolescence. It is important that young adults are made aware of this and educated on appropriate nutrition to understand where they can access omega 3 whilst limiting omega 6.