Plasma renin activity in depressed patients treated with increasing doses of lithium carbonate.

Plasma renin activity (PRA) was measured in the supine position and after active upright stance in patients with endogenous depression and in a group of healthy volunteers serving as controls. In the depressed patients, PRA was further investigated in the same conditions during treatment with increasing doses of lithium carbonate. Basal PRA values were lower in depressed patients than in normal controls, particularly in the upright stance, and tended to rise gradually during lithium therapy. These findings suggest that lithium may work as a stimulant of the renin-angiotensin system, and possibly as an antidepressant, by way of producing functional activation of the norepinephrine system independent of its action on the water and electrolyte balance.