Further examination of the data using the quartile categories of serum albumin revealed that the odds ratio (OR) for having depression reduced linearly across the quartiles of serum albumin in all models; either adjusted model 1 or unadjusted models 2 and 3 (P trend = <0.001, 0.009, and 0.001 respectively). The gene discussed is ALB; the disease is major depressive disorder.