Calcium and magnesium concentrations in affective disorder: difference between plasma and serum in relation to symptoms.

Morning (0800) plasma and serum and mean diurnal (24-h) serum calcium (Ca) and magnesium (Mg) concentrations were investigated in 56 depressed patients, 32 with acute major depression, 26 of these restudied in remission, 24 patients with longstanding depression, mainly treated with lithium, and in 27 healthy controls. All subjects were rated with the Comprehensive Psychopathological Rating Scale (CPRS). Significant differences between the groups were found for 0800 and 24-h serum Ca and Mg, 0800 plasma Mg, but not for 0800 plasma Ca. Elevations of serum Ca and Mg, plasma Mg but not plasma Ca were noted in the lithium-treated patients. Sex differences for plasma but not serum levels were seen in remission and in the controls. Depressive symptoms were negatively correlated to 0800 plasma Ca in the acute state and positively to 0800 and 24-h serum Ca and Mg in remission and longstanding depression. This difference between plasma and serum in relation to symptoms could reflect a change in a calcium binding factor present in plasma but not in serum, connected with biological factors of affective disease.