Individuals who suffer from depression have lower concentrations of zinc in their circulating blood compared to those without depression, according to the findings of a new meta-analysis published in the journal Biological Psychiatry.
Preliminary clinical trials have suggested that adding zinc to antidepressant therapy may produce more rapid or more effective improvement in depressive symptoms.
“A growing body of evidence demonstrates that experimental zinc deficiency can induce depressive-like behavior in animals, which can be effectively reversed by zinc supplementation,” wrote Walter Swardfager, Ph.D., from the Sunnybrook Research Institute, University of Toronto and colleagues.
Many, although not all, studies that have measured zinc concentrations of circulating blood in depressed and nondepressed individuals have suggested that depression might be associated with lower zinc concentrations in various population samples, the researchers said.
Depression is a serious mental illness characterized by overwhelming feelings of sadness, lack of energy or motivation, a low mood and other symptoms that last for more than two weeks. People with depression often find it difficult to do things in their everyday lives that ordinarily would be easy.
Researchers conducted this meta-analysis to determine whether the clinical evidence supports lower zinc levels in depressed patients compared with those without depression.
The analysis included 17 studies that measured blood–zinc concentrations in 1643 depressed patients and 804 control participants. Ten of these studies involved psychiatric inpatients, while seven studies involved community samples. Of the participants, 34.4 percent were male, and the mean age was 37.7 years.
The findings revealed that mean circulating blood–zinc concentrations were lower in depressed individuals compared with control participants. More severe depression was associated with greater differences in zinc levels between depressed and control participants.
“Although association studies cannot determine the direction of causation, a causal association between zinc status and depression is biologically plausible,” wrote the authors.
“Zinc has antioxidant properties, helps to maintain endocrine homeostasis and immune function, and plays multiple roles in regulating [brain circuits] and cognitive function.
“Thus, changes in zinc [balance] might compromise neuroplasticity and contribute to long-term neuropsychological and psychiatric decline,” they said.
Zinc is very important for immune function. Lower serum levels of zinc have been associated with abnormalities in fatty acid metabolism and in serum lipid levels, which might affect brain function and vascular health.
Lower zinc levels have also been associated with cardiovascular disease, a common comorbidity of major depressive disorder (MDD), the authors note.
“The pathophysiological relationships between zinc status and depression, and the potential benefits of zinc supplementation in depressed patients, warrant further investigation,” the researchers wrote.
Source: Biological Psychiatry