Abstract
Drug use determines a heteromorphic and complex psychic phenomenology which develops according to the substance type, the way of taking drugs and the the evolution stage. On the other way, the cannabis use burden with multiple controversies regarding the association with psychiatric symptomathology.
Patient B. I, 25 years, a computer scientist, from urban environment have presented psychotic symptoms, derealisation, depersonalisation, a consequence of the cannabis use-chronic use, for more than 2 years. In the last 3 months, the drug use was more frequently, about three times a week. He had the features of anxious personality disorder. While short term antipsychotic treatment have significantly alleviated the psychotic and cognitive symptoms, on long term the patient experienced more other symptoms like anhedonia, generalized anxiety and obsessive-compulsive elements.
Psychosis is an inconstant complication of the cannabis use but is often cited in the speciality literature. The substrate of such a complication is hyperdopaminergia in the mesolimbic system and is associated with different risk factors. When GABA is blocked by THC, the result is increased dopamine release. Cannabis withdrawal can manifest with long term residual symptoms owing to the drug storage at the adipose tissue. In this case, we talk about the Post-acute withdrawal syndrome consisted in an amotivational syndrome and an obssesive-compulsive syndrome due to the neurotransmitters alterations (dopamine, endocannabinoids, serotonin). DA dysfunction underlines anhedonia, whereas 5-HT dysfunction causes obsessive thoughts.

Key words: cannabis, psychosis, amotivational syndrome, post-acute withdrawal syndrome