OPN1MW and schizophrenia: However, a third RCT employing CBD as an add‐on therapy did not report any improvements in cognition or symptoms of schizophrenia after a lower average dose of 10 mg/kg/d over 6 weeks (n = 36).14 An acute dose of 5 or 10 mg/kg/d did not improve selective attention in a placebo‐controlled trial of 28 schizophrenia patients.30 A number of case studies have also been conducted by Zuardi and colleagues in this medical context.