GPR39 and major depressive disorder: GPR39 is being investigated in relation to cardiovascular diseases [6], neurovascular diseases [7], diseases of the central nervous system (CNS) such as depression [8,9] or epilepsy [10,11], bone diseases [12], etc. Both elements—zinc and magnesium—play significant roles in the aforementioned conditions, more specifically in cardiovascular diseases [13,14], depression [15], epilepsy [16], or diseases of bones [17,18,19].