This paper intends to examine a new kind of clinical psychiatric syndrome, called by the author "synthetic psychosis", which can occur in people who abuse novel psychoactive substances (NPS). This syndrome will be considered from both a psychopathological and a phenomenological perspective. The contemporary trend of poly-abuse of NPS in young people can lead to a sort of very intense paraphrenic state characterised by continuous hallucinations and formed by a mental automatism syndrome and by secondary (interpretative) delusions. The clinical case of G., discussed in this paper, is an exemplary case of this synthetic psychosis. The psychopathological understanding of the core symptomatology of the patient examined has been fundamental for the successive therapeutic approach. If this attempt at understanding is ineffective, the frequent consequences include the worsening of the psychopathology and addiction, the patient's admission into a psychiatric hospital, his/her arrest for crimes related to antisocial behaviour, a diffusion of infective diseases commonly found in addicts, more frequent overdoses, aggressive behaviour, an increase in the costs of public health system and, finally, the suicide of the patient.