The primary aim of this study was to examine treatment attendance and stimulant use in one ‘parallel outcomes’ model in order to determine how these two related outcomes impact one another during stimulant use disorder treatment.

In one trial, contingency management (CM) was positively associated with attending treatment throughout the trial (β = 0.060, p < 0.05), but it was not related to urinalysis (UA) status during the trial.

In the second trial, CM positively predicted ⁻UA over the 12-week treatment period (β = 0.069, p < 0.05), and CM was not associated with attendance during the treatment period.

In both trials, there was a significant, positive relationship between attendance and ⁻UA submission. In the first trial a ⁻UA at both baseline and over time was related to attendance over time (r = 0.117; r = 0.013, respectively, p < 0.05), but in the second trial only baseline ⁻UA submission was related to attendance over time (r = 0.055, p < 0.05).

These findings indicate that stimulant use and treatment attendance over time are related but distinct outcomes that, when analyzed simultaneously, portray a more informative picture of their predictors and the separate trajectories of each.