The MR analyses provide putative evidence for bidirectional causal effects between psychotic disorders and the cannabis phenotypes. We observed robust evidence supporting the genetic liability to SCZ causally increases the risk of both cannabis phenotypes. This is in line with previous findings9,17,58. We present novel putative evidence that the genetic liability to LCU increases BIP risk. A previous bidirectional MR study only found the genetic liability to BIP increased the risk of LCU,59 which we also observed. Using the latest and largest BIP GWAS likely aided this discovery. However, the CAUSE method could not distinguish causality from effects due to a shared factor related to both LCU and BIP. Additionally, the lack of power in the LCU GWAS may affect the validity of this finding. We caution readers on concluding that psychotic disorders cause cannabis use, and that cannabis use does not cause psychotic disorders. It is important to consider the large difference in the number of genetic variants included in the analyses testing forward (cannabis-to-psychosis) and reverse (psychosis-to-cannabis) causal associations. Given current GWAS, the power to detect reverse causation
