Classical observational studies into the causal relationship between a risk factor and a disease sometimes result in contradictory and spurious findings. This is due to confounding factors. It is not possible to conclude from the results of classical observational studies whether a specific risk factor may be a suitable target for future treatments. A solution is to conduct a Mendelian randomization analysis, which uses genetic variation as a surrogate marker for the risk factor. Mendelian randomisation is based on the idea that characteristics and environmental factors are proportionately divided into carriers and non-carriers of various genetic variants. Mendelian randomisation can be used only if there is a robust relationship between the genetic variant and the risk factor, if the genetic variant is not associated with other factors that confound the relationship between the risk factor and the disease, and if the genetic variant has an effect on the disease only via the risk factor, i.e. not via other biological mechanisms.