According to the so-called "Two hit" hypothesis in the development of schizophrenia, there are two periods of increased vulnerability. The first one is in a fetal age when it comes to the interaction of genetic and environmental factors such as infection and inflammatory processes who may also serve this function. The second period of vulnerability is a period of adolescence, or early adult age when the influence of environmental factors leads to clinical manifestations of the disease. It is thought that cytokines have key role in the first strike.