Differences and variability in plasma noradrenaline between depressive and anxiety disorders.
Plasma noradrenaline (NA) levels were compared between two groups of patients with major depressive disorder (melancholic/psychotic and non-melancholic), patients with general anxiety disorders and healthy controls. The melancholic/psychotic depressed group had the highest plasma NA levels. This only reached statistical significance with respect to the control group. Within the depressed group, there was no association between plasma NA levels and age, weight loss, ratings of depression, anxiety or plasma cortisol levels. Variance of plasma NA was greatest in the melancholic/psychotic depressed group. A review of previous studies shows an association between raised plasma NA, depressive illness and alterations in NA variance. This association may be limited to melancholic/psychotic depressed patients. The above findings support a dysregulated noradrenergic system in depressive illness.