Re: Caution urged in interpreting a negative study of cannabis use and schizophrenia: A response to Dr. Christine Miller

摘要

On behalf of my co-authors, I thank Dr. Miller for her thoughtful comments about our study (Proal et al., 2014). However, her title is quite misleading in that it implies that our study was "negative" and that we were simply reporting that cannabis does not "cause" schizophrenia. This is not so; unfortunately one sentence in the conclusion was taken out of context and as such was misleading. Our study was a family study of people who did and did not abuse cannabis as adolescents. There were 4 groups: non-psychotic individuals who did and did not abuse cannabis and people with schizophrenia who did and did not abuse cannabis prior to their illness. What the main study analysis showed was that those individuals who developed schizophrenia after cannabis use in adolescence had a significantly greater family history of schizophrenia than those who used cannabis and did not develop schizophrenia and an elevated family history no different than those with schizophrenia who never used cannabis. These results suggest that the key element for determining whether someone develops schizophrenia after cannabis use is an elevated genetic risk.