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

We appreciate Dr Young Ho Lee’s interest in our study on the relationship between psoriatic arthritis (PsA) and osteoporosis,1 and thank him for the comments brought in his letter.2 Over the past few years, several methods were developed to deal with the pleiotropic effect of instrumental single-nucleotide polymorphisms (SNPs) in Mendelian randomisation (MR) analysis, such as inverse variance-weighted (IVW), MR Egger, the weighted median,3 weighted (simple) mode-based4 and Mendelian Randomization Pleiotropy RESidual Sum and Outlier (MR-PRESSO).5 However, the limitation of each method should be acknowledged.6 The weighted median method estimated some SNPs as invalid instruments, but …