A team of US and Norwegian investigators claim to have found for the first time a link between nutrition and depression vulnerability.
Martha Morris and colleagues from Tufts University and Harvard Medical School report in Psychotherapy and Psychosomatics that depressed people among the general US population often had low blood folate levels. They say that folate supplementation during the year following a depressive episode may help recovery.
The researchers report that folate deficiency and low folate status are linked in clinical studies to depression, persistent depressive symptoms, and poor antidepressant response. These relationships have not been demonstrated in general populations so they examined associations between depression and folate status indicators in an ethnically diverse population sample, aged between 15 and 39 years old.
Healthy subjects whose red blood cell (RBC) folate concentrations had been measured were divided into three groups : 2,526 had no depression, 301 had major depression and 121 were diagnosed with dysthymia (less severe than 'major depression' but can also trigger major depressive episodes).
Serum levels of folate and total homocysteine (tHcy) were also measured. The team adjusted for sociodemographic factors, serum vitamin B12 concentration, alcohol consumption over the past year and other factors including overweight and use of vitamin/mineral supplements, cigarettes and illegal drugs.
The results showed that those with a lifetime diagnosis of major depression had lower blood folate levels than people who had never been depressed. Subjects who had been diagnosed with dysthymia alone had lower red blood cell folate concentrations than never-depressed subjects, but the serum folate concentrations of the two groups were comparable. Total homocysteine was not related to lifetime depression diagnoses.
Low folate status was found to be most characteristic of recently recovered subjects, according to the researchers, and a large proportion of such subjects were folate deficient.
The study shows that folate supplements may be important during the year following a depressive episode.