Why caution should be applied when interpreting and promoting findings from Mendelian randomisation studies.

INTRODUCTION In their article entitled'Investigating genetic causal relationships between blood pressure and anxiety,depressive symptoms,neuroticism and subjective well-being',Cai and colleagues1 presented the results of a two-sample Mende-lian randomisation2(MR)study examining associations between blood pressure traits(systolic,diastolic,hypertension and pulse pressure)and psychological traits(anxiety,depression,neuroticism and subjective well-being).