To evaluate relative expression of genes with the potential to translate environmental stimuli into long-term alterations in the brain, namely early growth response (EGR)1, EGR3, and cryptochrome circadian regulator (CRY)2 genes, in peripheral blood from patients with bipolar disorder (BD), schizophrenia (SZ), and major depressive disorder (MDD) and from healthy controls (HC). The gene discussed is EGR1; the disease is bipolar disorder.