Ruusunen A, 2013 - Diet and Depression: An Epidemiological Study

Abstract:

The association between diet and depression has previously mainly been studied in cross-sectional studies, and only few prospective studies have been published.  The evidence suggests that folate and long-chain n-3 polyunsaturated fatty acids (PUFAs) may be connected to the decreased risk of depression.  Furthermore, only few studies have concentrated on the association between general dietary patterns and depression.  

The aim of this thesis was to investigate whether dietary intake of folate and vitamin B12, serum concentrations of n-3 PUFAs, consumption of coffee and tea, or caffeine intake are associated with the risk of getting a discharge diagnosis of severe depression in population based sample (the Kuopio Ischaemic Heart Disease Risk Factor (KIHD) Study, n=2,077- 2,313, works I, II and III) of middle-aged or older Eastern Finnish men during an average of 13-20 years of follow-up.

In addition, the study focused on examining if dietary patterns are associated with the prevalence of depressive symptoms or the risk of depression requiring hospital treatment (the KIHD Study, n=1,003, work IV).

Finally, the aim was to investigate how an intensive lifestyle intervention affects the depressive symptoms in an intervention study design (the Finnish Diabetes Prevention Study (DPS), n=140, work V).  

It was observed that increased intake of folate and healthy dietary patterns (consumption of vegetables, fruits, berries, whole-grains, poultry, fish and low-fat cheese) were associated with a lower risk of depression. In addition, increased coffee consumption was non-linearly associated with a decreased risk of depression.

Vitamin B12 intake, serum concentrations of n-3 PUFAs, serum ratio of n-6 to n-3 PUFAs, tea drinking and caffeine intake were not related to the risk of depression.  Adherence to unhealthy dietary pattern (consumption of sausages, processed meats, sugar-containing desserts and snacks, sugary drinks, manufactured foods, French rolls and baked or processed potatoes) was associated with an increased prevalence of elevated depressive symptoms.

In addition, participation in the three-year lifestyle intervention study improved depression scores with no specific group effect, although clinically non-significantly. Reduction of body weight was associated with a greater reduction in depressive symptoms.  

The results of this thesis indicate that diet, especially a healthy diet rich in folate, and a dietary pattern rich in vegetables, fruits, berries, whole-grains, poultry, fish and low-fat cheese, may be protective against depression. N-3 PUFAs may not have a role in the prevention of depression, at least not in middle-aged or older men with generally low circulating concentrations of n-3 PUFAs.