Response to: 'Correspondence on 'Systemic evaluation of the relationship between psoriasis, psoriatic arthritis and osteoporosis: observational and Mendelian randomisation study' by Lee.

We would like to thank the interests and comments from Cui et al 1 on our study2 entitled ‘Systemic evaluation of the relationship between psoriasis, psoriatic arthritis and osteoporosis: observational and Mendelian randomization study’. Here, we responded the comments point by point.\n\nFirst, the potential confounders we included were age, sex, height, weight, smoking status, drinking status, regular physical activity and mediation treatment. The selected confounders were known potentially to have effect on the outcome (bone mineral density, BMD),3 and were typically recorded in UK Biobank dataset. The mediation analysis suggested that 63% of the effect of psoriatic arthritis (PsA) on BMD were mediated by treatment with methotrexate or ciclosporin; thus, there were many other unmeasured confounders to be discovered. In addition, we excluded participants …