Abstract
Polyunsaturated fatty acids (PUFAs) may be pertinent to the development of mental disorders, for example via modulation of inflammation and synaptogenesis. We wished to examine cross-sectional and longitudinal associations between PUFAs and mental disorders in a large cohort of young people. Participants in the Avon Longitudinal Study of Parents and Children were interviewed and provided blood samples at two sampling periods when approximately 17 and 24 years old. Plasma PUFA measures (total omega-6 [n-6], total omega-3 [n-3], n-6:n-3 ratio and docosahexaenoic acid [DHA] percentage of total fatty acids) were assessed using nuclear magnetic resonance spectroscopy. Cross-sectional and longitudinal associations between standardised PUFA measures and three mental disorders (psychotic disorder, moderate/severe depressive disorder and generalised anxiety disorder [GAD]) were measured by logistic regression, adjusting for age, sex, body mass index and cigarette smoking. There was little evidence of cross-sectional associations between PUFA measures and mental disorders at age 17. At age 24, the n-6:n-3 ratio was positively associated with psychotic disorder, depressive disorder and GAD, while DHA was inversely associated with psychotic disorder. In longitudinal analyses, there was evidence of an inverse association between DHA at age 17 and incident psychotic disorder at age 24 (adjusted odds ratio 0.44, 95% confidence interval 0.22–0.87) with little such evidence for depressive disorder or GAD. There was little evidence for associations between change in PUFA measures from 17 to 24 years and incident mental disorders at 24 years. These findings provide support for associations between PUFAs and mental disorders in early adulthood, and in particular, for DHA in adolescence in relation to prevention of psychosis.
Highlights
Fatty acids are the major metabolic products of lipid metabolism
We considered four polyunsaturated fatty acids (PUFAs) measures as exposures in the current study: total n6 fatty acids; total n-3 fatty acids; n-6: n-3 fatty acid ratio; and docosahexaenoic acid (DHA) expressed as percentage of total fatty acids
We examined the following prenatal socio-economic factors: family home ownership status during pregnancy as measured by a questionnaire completed by mothers at 8 weeks gestation; highest maternal educational qualification as measured by a questionnaire completed by mothers at 32 weeks gestation; and parental social class based on occupation of the participant’s mother or father as measured by a questionnaire completed by mothers at 32 weeks gestation
Summary
Fatty acids are the major metabolic products of lipid metabolism. They are categorised by number of carboncarbon double bonds: saturated fatty acids have none, monounsaturated fatty acids have one and polyunsaturated fatty acids (PUFAs) have two or more. PUFAs are further subdivided by the position of the first carboncarbon double bond from the methyl end of the molecule. This occurs at the sixth carbon atom in omega-6 PUFAs and the third in omega-3 PUFAs. Omega-6 (n-6) PUFAs, such as linoleic acid and arachidonic acid, produce n-6 eicosanoids which have broadly pro-inflammatory effects. Alpha-linolenic acid cannot be synthesised by humans and must be obtained directly from dietary intake. Humans can convert ALA into EPA and DHA, the efficiency of this conversion is limited and EPA and DHA must be obtained
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