The study by Finland researchers among 3,000 middle-aged and elderly Finnish subjects found that lack of certain nutrients ups the risk of melancholic depressive symptoms but has no effect on non-melancholic depressive symptoms.
Melancholic depression involves typical depressive symptoms, such as a depressed mood. Non-melancholic depression is characterised by other types of symptoms, such as low self-esteem and feelings of worry and anxiety.
Based on these new observations, melancholic and non-melancholic depression may be separate depressive subtypes with different etiologies in terms of proinflammation and diet, researchers said.
"The findings have practical implications in the care of patients with depressive symptoms. For example, it may be wise to avoid medication causing weight gain among patients with non-melancholic depression, whereas melancholic depressive symptoms may call for a closer look at the quality of the patient's diet," said Jussi Seppala, Chief of the Department of Psychiatry of the Hospital District of Southern Savo.
Among subjects with the highest folate intake, the risk for melancholic depressive symptoms was almost 50 per cent lower than among those with the lowest intake.
In addition, among those with the highest vitamin B12 levels, the risk for melancholic depressive symptoms was almost three times lower than among those with the lowest levels.
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A similar association with non-melancholic depressive symptoms was not observed.
Another observation was that the risk for the metabolic syndrome was twofold among those with non-melancholic depressive symptoms, as compared to those with melancholic symptoms or those with no depressive symptoms.
The findings were published in Journal of Affective Disorders.