Schizophrenia is usually diagnosed in late adolescence or early adulthood but there are forms of the illness which occur in childhood (before 12) and adolescence (between 12 and 18). Such early-onset schizophrenia can be particularly debilitating and severe. There has been little research into the effectiveness of antipsychotic drugs for treating schizophrenia in such young age groups but a U.S. study of 16 children found that 12 of them, treated with olanzapine for 10 weeks showed significant improvements by the end of the trial. The children did gain quite a bit of weight (which is also a side effect in adults) and on average put on a stone. Two of the children also experienced other side effects from the drugs.
Quintana, Humberto ... [et al] - An open-label study of olanzapine in children and adolescents with schizophrenia Journal of Psychiatric Practice March 2007, 13(2), 86-96