I think that this is a complicated issue.

There is good evidence that medicinal cannabis can help people with neuropathic pain, the loss of appetite associated with AIDS and the nausea associated with cancer chemotherapy.

Many people with schizophrenia smoke cannabis and it has been argued that cannabis smoking is risk factor for schizophrenia. For example, cannabis use is strongly related to the age of onset and morbidity of schizophrenia.

I think that a lot more work needs to be done before (depending on its results) medicinal cannabis can be safely recommended for people with schizophrenia.