The experience of the psychosis can open a critical window into primary psychiatric conditions, particularly schizophrenia or bipolar disorder. More recently, the role of environment in early adolescence or late childhood, including psychological abuse or physical violence, has been associated with a greater likelihood of developing psychosis years later. Evidence has also shown, even in symptomatic remission, the occurrence of cognitive symptoms, particularly in complex attention, executive functioning, episodic memory, and verbal and procedural IQ. The current chapter discusses the epidemiology of first episode psychosis, neurobiological characteristics, and main risk factors, including early exposure to the trauma situation and early interventions.