It is difficult to distinguish between posttraumatic and idiopathic psychotic disorders. After a traumatic brain injury, the incidence of psychotic symptoms is between 5–20%, with an average duration of 4 years. Delusions and auditory hallucinations are more frequent than negative and catathoniform symptoms. Despite the lack of strong scientific evidence, antipsychotic treatment seems the best choice, although there is a bigger risk of adverse effects. The prognosis does not seem to be related to the severity of the injury.

We intend to illustrate the daily clinical practice, in which we find patients with important comorbidities, difficult differential diagnosis and therapeutic challenges.

Using a case-report format, we describe a 26 year old patient with the following diagnostics: traumatic brain injury with secondary psychotic symptoms versus schizophrenia; alcohol abuse; cannabis dependence; pathologic gambling. We summarize complementary explorations, therapeutic management and evolution.

Along three years of follow up there is a preponderance of negative symptoms. Positive symptom exacerbations also occur, in coincidence with an increase of cannabis consumption. Due to lack of compliance, long acting antipsychotics are prescribed. Motivational Interview is used for the drug use disorders and the treatment compliance, achieving the goal of reducing cannabis consumption.

Daily clinical practice brings us highly complex cases in which a multidisciplinary approach is very important. This particular case shows the differential diagnose difficulties between posttraumatic and idiopathic psychosis, and the troubles of clinical and therapeutical management in the dual pathology field.