CBD has shown in studies to have a positive effect on those suffering with schizophrenia. A study published in 2017 showed how CBD, taken alongside their prescribed medication had a positive effect on symptoms when compared to the control group who took medication alone.
Their studies included two groups with just over 40 participants in each and each group took 1000mg of CBD a day. After 6 weeks of treatment, their symptoms had shown to have improved with an improvement in cognition.
You can view the study by McGuire et al (2017) here.