ICAM-1 is of interest in psychiatric disorders for two reasons: 1) It has a key function in the blood–brain barrier (BBB), which plays an important role in the biology of psychiatric disorders by regulating the movement of molecules from the peripheral body, in particular components of the immune system, into and out of the CNS (see 2.1), and 2) it is a marker for inflammation. The gene discussed is ICAM1; the disease is psychiatric disorder.