Nowadays, it is not questioned that the blood-brain barrier plays an extremely important role in isolating central nervous system structures from peripheral tissues, but in the early stages ofmedical research and life sciences, its existence was not clearly defined. Better understanding of the real structure took a long time and needed new techniques. Currently, researchers are still focusing on the blood-brain barrier in conditions of the nervous system like mental disorders, since it is increasingly important to get closer to the understanding the exact function of this barrier. This short summary gives an insight into these problems.  Kulcsszavak: vér-agy gát, történelmi áttekintés, depresszió