There is evidence that the normally transitory developmental expression of psychosis (psychosisproneness) may first of all become abnormally persistent (persistence) and later on become clinically relevant (impairment), depending on the amount of environmental risk to which the person is exposed. According to the psychosis-proneness-persistence impairment model, genetic background factors can impact on a transitory expression of psychosis. Whether or not this will lead to a poor prognosis in terms of persistence and clinical need will depend on the interaction between environmental exposure and genetic risk.