There is evidence for associations between polyunsaturated fatty acids (PUFAs) such as  docosahexaenoic acid (DHA) and psychosis risk(1-3). However, the existing literature has focused on  PUFA measurements at single timepoints(4,5) , which may overlook dynamic patterns of variability  over time. The aims of this study were: 1) To describe longitudinal trajectories of plasma omega6:omega-3 ratio and DHA in a large general population sample; and 2) To evaluate associations  between trajectories and psychosis-spectrum outcomes in early adulthood. 
We performed a cohort study within the Avon Longitudinal Study of Parents and Children. 3635  participants completed psychiatric assessments at age 24 years (2247 [61.8%] female).  Participants provided plasma samples at four timepoints when aged 7, 15, 17 and 24. Plasma  omega-6:omega-3 ratio and DHA levels (% total fatty acids) were measured using nuclear  magnetic spectroscopy, then standardised by sex. Psychosis-spectrum outcomes were assessed at age 24. Psychotic experiences (PEs) and  psychotic disorder were assessed using the Psychosis-Like Symptoms interview (PLIKSi), as was  the total number of PEs (range 0 to 11). Negative symptoms score (range 0 to 10) was measured  using the Community Assessment of Psychic Experiences. Curvilinear growth mixture modelling was used to derive longitudinal trajectories of plasma  omega-6:omega-3 ratio and DHA levels over time. Trajectories were adjusted contemporaneously  for body mass index at each timepoint. Associations between trajectory membership and  outcomes were adjusted for sex, ethnicity, parental socioeconomic class, smoking and alcohol  use. 
A three-trajectory solution was optimal for omega-6:omega-3 ratio (stable average, n=3282 [90.3%]; slightly above average, n=61 [1.7%]; and persistently high, n=292 [8.0%]) and DHA  (stable average, n=2739 [75.4%]; persistently high, n=245 [6.7%]; and persistently low, n=651  [17.9%]). Relative to stable average, trajectories characterised by persistently high omega-6:omega-3 ratio  and persistently low DHA were associated with increased odds of PEs and psychotic disorder in  unadjusted analyses, but these associations attenuated on adjustment for covariates. Conversely,  the persistently high omega-6:omega-3 ratio trajectory was associated with increased number of  PEs (adjusted β 0.41, 95% confidence interval [CI] 0.05-0.78, p=0.026) and negative symptoms  (adjusted β 0.43, 95%CI 0.14-0.72, p=0.004). Similarly, the persistently low DHA trajectory was  also significantly associated with increased number of PEs (adjusted β 0.45, 95%CI 0.14-0.76,  p=0.004) and negative symptoms (adjusted β 0.35, 95%CI 0.12-0.58, p=0.003).
Persistently high plasma omega-6:omega-3 ratio and persistently low plasma DHA were  associated with increased PEs and negative symptoms of psychosis at age 24. Optimisation of  PUFA status during development warrants further investigation in relation to psychosis-spectrum  outcomes in early adulthood. Limitations include that causality cannot be inferred and residual  confounding is possible. Attrition occurred along a socioeconomic gradient, although we used  multiple imputation to avoid complete-case biases. Strengths include the use of a wellcharacterised cohort, and the use of biomarker measurement of plasma PUFAs. 
References  
1. Adan RAH, van der Beek EM, Buitelaar JK, et al. (2019) Eur Neuropsychopharmacol 29(12), 1321- 1332. 
2. Jones HJ, Borges MC, Carnegie R, et al. (2021) Lancet Psychiatry 8(12), 1062-1070. 
3. Hoen WP, Lijmer JG, Duran M, et al. (2013) Psychiatry Res 207(1-2), 1-12. 
4. Mongan D, Healy C, Jones HJ, et al. (2021) Translational Psychiatry 11(1), 321. 
5. Thompson AD, Jones HJ, Heron J, et al. (2020) Schizophrenia Res 224, 108-115. 
6. Boyd A, Golding J, Macleod J, et al. (2013) Int J Epidemiol 42(1), 111-127. 
7. Fraser A, Macdonald-Wallis C, Tilling K, et al. (2013) Int J Epidemiol 42(1), 97-110 
8. Horwood J, Salvi G, Thomas K, et al. (2008) Br J Psychiatry 193(3), 185-91. 
9. Stefanis NC, Hanssen M, Smirnis NK, et al. (2002) Psychol Med 32(2), 347-58.

OC22 - Longitudinal trajectories of plasma polyunsaturated fatty acids and associations with psychosis-spectrum outcomes in early adulthood

Unique to the new Congress (previously the Summer Conference) is that you will have greater opportunity to engage with more nutrition science than ever before. In 2024 the core programme will be delivered by the Irish Section of The Nutrition Society, supported by the Science Committee. The theme of these symposia will be ‘new data – focused approaches and challenges’. Outside of the core programme you will have the chance to hear the latest research from the Society’s partner organisations, universities, the private sector and more, on a diverse range of research.