Since the seminal study of Steinbeck and Durell (1968), few epidemiological studies have attempted to replicate whether psychosocial stress precipitates the onset of a first psychotic episode. Our aim was to support or refute the finding of elevated psychosis incidence in the first month of army induction and to examine factors impacting the timing of onset. Data were collected from medical files of 186 army conscripts, hospitalized with a diagnosis of First Episode Psychosis (FEP) between 2005 and 2014 in the Psychiatric Military Hospital in Athens, Greece. FEP rates were at least 4.5 times higher in the first month of military service, compared with any other month. Earlier FEP onset was associated with rural environment at the time of birth, multiple drug use and service away from home. Psychosocial stress precipitates FEP, particularly in those exposed to other risk factors.