There is compelling evidence to suggest the hypothesis that neurological signs represent a trait feature of schizophrenia.

Objective: To compare the efficacy, safety, and tolerability of olanzapine and quetiapine in adolescents with first episode psychosis. Method: Fifty adolescents (age 16 ± 1.25) with a first episode of psychosis were randomized to quetiapine or olanzapine in a 6-month open label study. Efficacy and side effect scales, as well as vital signs and laboratory data were recorded at baseline, 7, 15, 30, 90, and 180 days (end of study). Results: Out of the total sample included in the study, 32 patients completed the trial (quetiapine n = 16, olanzapine n = 16). Patients in both treatment groups had a significant reduction in all clinical scales with the exception of the negative scale of the Positive and Negative Symptom Scale (PANSS) for olanzapine and the general psychopathology scale of the PANSS for quetiapine. The only difference between treatment arms on the clinical scales was observed on the patients' strength and difficulties questionnaire (SDQ) scale, with greater improvement for olanzapine. Patients on olanzapine gained 15.5 kg and patients on quetiapine gained 5.5 kg. Conclusion: Olanzapine and quetiapine reduced psychotic symptoms in this adolescent sample. Patients on olanzapine gained significantly more weight. Side effects with both drugs seemed to be more prevalent than those reported in adult studies

Cognitive impairment in EOP is already present at the first episode, and cognitive development seems to be arrested early in EOP patients compared to their healthy peers, at least for some cognitive functions. These and previous similar results support the neurodevelopmental hypothesis of psychosis.