GSTM1 and major depressive disorder: Cardiac rehabilitation, Luria–Nebraska Neuropsychological Battery‐screening test, sex, BMI, ischaemic cardiomyopathy, hypertension, DM, AF, mean blood pressure, heart rate, LVEF, serum sodium, Hb, beta‐blockers, ACEI/ARB/ARNI, Beck Anxiety Inventory, Beck Depression Inventory‐II, old stroke, eGFR and albumin