Titova OE, Michaëlsson K, Vithayathil M, et al. - In this study, the potential causal relationship of sleep duration with overall and site‐specific cancers was evaluated applying the Mendelian randomization (MR) design. Researchers applied single‐nucleotide polymorphisms associated with the sleep traits identified from a genome‐wide association study as instrumental variables to calculate the relationship with overall cancer and 22 site‐specific cancers among 367,586 UK Biobank participants. The MR study does not serve strong proof to support causal relationships of sleep duration with the risk of overall and site‐specific cancers. Further MR studies are needed.