Dietary intake of fish, omega-3, omega-6 polyunsaturated fatty acids and vitamin D and the prevalence of psychotic-like symptoms in a cohort of 33,000 women from the general population.
BACKGROUND
Low intake of fish, polyunsaturated fatty acids (PUFA) and vitamin D deficiency has been suggested to play a role in the development of schizophrenia. Our aim was to evaluate the association between the intake of different fish species, PUFA and vitamin D and the prevalence of psychotic-like symptoms in a population-based study among Swedish women.


METHODS
Dietary intake was estimated using a food frequency questionnaire among 33,623 women aged 30-49 years at enrollment (1991/92). Information on psychotic-like symptoms was derived from a follow-up questionnaire in the years 2002/03. Participants were classified into three predefined levels: low, middle and high frequency of symptoms. The association between diet and psychotic-like symptoms was summarized in terms of relative risks (RR) and corresponding 95% confidence intervals and was evaluated by energy-adjusted multinomial logistic regression.


RESULTS
18,411 women were classified as having a low level of psychotic-like symptoms, 14 395 as middle and 817 as having a high level. The risk of high level symptoms was 53% (95% CI, 30-69%) lower among women who ate fish 3-4 times per week compared to women who never ate fish. The risk was also lower for women with a high intake of omega-3 and omega-6 PUFA compared to women with a lower intake of these fatty acids. The effect was most pronounced for omega-6 PUFAs. The RR comparing the highest to the lowest quartile of omega-6 PUFAs intake was 0.78 (95% CI, 0.64-0.97). The associations were J-shaped with the strongest reduced risk for an intermediate intake of fish or PUFA. For fatty fish (herring/mackerel, salmon-type fish), the strongest inverse association was found for an intermediate intake (RR: 0.81, 95% CI, 0.66-0.98), whereas a high intake of fatty fish was associated with an increased risk of psychotic-like symptoms (RR: 1.90, 95% CI, 1.34-2.70). Women in the highest compared with the lowest quartile of vitamin D consumption experienced a 37% (95% CI, 22-50%) lower risk of psychotic-like symptoms.


CONCLUSIONS
Our findings raise a possibility that adult women with a high intake of fish, omega-3 or omega-6 PUFA and vitamin D have a lower rate of psychotic-like symptoms.
Hedelin
Maria
M
Department of Neuroscience, Psychiatry, Ulleråker, Uppsala University, Uppsala, Sweden. maria.hedelin@ki.se
Löf
Marie
M
Olsson
Marita
M
Lewander
Tommy
T
Nilsson
Björn
B
Hultman
Christina M
CM
Weiderpass
Elisabete
E
D000328:Adult; D000818:Animals; D015331:Cohort Studies; D004032:Diet / Q000706:statistics & numerical data*; D004034:Diet Surveys; D004041:Dietary Fats / Q000378:metabolism; D015525:Fatty Acids, Omega-3 / Q000378:metabolism*; D043371:Fatty Acids, Omega-6 / Q000378:metabolism; D005247:Feeding Behavior / Q000145:classification*; D005260:Female; D005399:Fishes / Q000378:metabolism*; D006801:Humans; D008875:Middle Aged; D015995:Prevalence; D011618:Psychotic Disorders / Q000453:epidemiology* / Q000517:prevention & control; D012307:Risk Factors; D012559:Schizophrenia / Q000453:epidemiology* / Q000209:etiology / Q000517:prevention & control; D017747:Seafood; D011795:Surveys and Questionnaires; D013548:Sweden / Q000453:epidemiology; D014807:Vitamin D / Q000378:metabolism*
D004041:Dietary Fats; D015525:Fatty Acids, Omega-3; D043371:Fatty Acids, Omega-6; D014807:Vitamin D