In Los Angeles, USA men who have sex with men and also did Chemsex (sex in the context of mephedrone or tina) who get diagnosed with an STI (sexually transmitted infection) were found to radically reuce their drug use afterwards.
They asked participants to fill out a questionnaire about what their sex life is like currently, and then compare some 24 months later.
Results: they were using some 30% less drugs thn before they were diagnosed with an STI (gonorrhea, syphiis, chlamydia or HIV).
Also, the number of people they had sex with dropped by more than half.
Either this shock of being positive or another reason put them in a nearly zero risk bracket for STIs.
If you do Chemsex and would like tot chat to me about it, please feel totally free to use the contact page with ccomplete confidentiality.