Using data from the French "Methaville" trial, Roux et al (Roux, Michel et al. 2012; Roux, Lions et al. 2013) investigated the effect of pre-treatment and in-treatment factors on long-term non-adherence to this OMT. Four pre-treatment predictors of non-adherence were identified: being female, not having stable housing, alcohol consumption and cocaine use. These findings highlight the need to appropriately assess psychoactive drug use when starting OMT, and urine drug testing should be consider as a way to reach this aim.