Psychometric properties of the Spanish simultaneous alcohol and cannabis motives measure (S-SMM) and its short form (S-SMM-SF) among young adults

<i>Background:</i> Simultaneous Alcohol and Cannabis (SAC) use is associated with greater negative consequences than individual use. Motives to use are robust predictors of alcohol and cannabis consumption, both separately and simultaneously. Despite the recent development of both a SAC motives measure and its short form, no Spanish adaptation is currently available. <i>Objectives:</i> To provide a Spanish adaptation of the full-length and short-form versions of the simultaneous alcohol and cannabis motives measure and to examine its psychometric properties in a sample of young adult SAC users. <i>Methods:</i> A targeted sampling procedure was used to recruit 612 young cannabis users, of whom 479 reported SAC use (18–25 years old [<i>M</i> = 21.01, SD = 2.14]; 36% female). Following adaptation and translation, participants completed the scale, along with measures of frequency of alcohol, cannabis, and simultaneous use, cannabis motives, and alcohol- and cannabis-related negative consequences. <i>Results:</i> Confirmatory factor analyses showed a four-factor structure (conformity, positive effects, calm/coping, and social). Moreover, the results indicated acceptable internal consistency (.70–.88), providing evidence of convergent, discriminant, and predictive validity for most dimensions. <i>Conclusions:</i> The results suggest that both versions of the scale are valuable tools for assessing motives for SAC consumption among young adults. These scales could aid in investigating motives for SAC use and informing interventions to mitigate associated harms.