Date of Award

Summer 8-2021

Degree Type


Degree Name

Doctor of Philosophy (PhD)



Committee Chair

Randy Arnau, Ph.D.

Committee Chair School


Committee Member 2

Brad Green, Ph.D.

Committee Member 3

Dan Capron, Ph.D.

Committee Member 3 School


Committee Member 4

Rich Mohn, Ph.D.

Committee Member 4 School



The growing body of research examining simultaneous alcohol and marijuana (SAM) use suggests motivations for alcohol-only, marijuana-only, and SAM use, especially among college-aged people, warrant further examination to ultimately tailor interventions to not only specific substances but also the underlying motivations for using those substances. Thus, the purpose of the present study was to test the measurement invariance of a novel broadband motives measure, the Motivations for Using Substances Questionnaire (MUSQ), across alcohol-only, marijuana-only, and SAM users and further test motivations’ relationships to use-related problems. However, due to insufficient sample sizes of marijuana-only users (n = 175), the MUSQ was subjected to two-group invariance testing across alcohol-only (n = 461) and SAM users (n = 374).

Confirmatory factor analysis of the MUSQ revealed an 8-factor baseline model that combined items developed from the MUSQ’s piloting study related to (a) reducing anxiety and unpleasant arousal, reducing negative affect, and increasing positive affect under one latent variable (Manage Emotional States; MES) and (b) using to manage negative social interactions with conformity motives under one latent variable (Manage Negative Social Interactions – Revised; MNSI-r). Configural and metric invariance were observed and partial invariance at the scalar level was demonstrated for the MUSQ across groups. SAM users tended to use more frequently for all motives except MNSI-r than alcohol-only users. MES motives consistently predicted use-related problems across groups. Thus, the MUSQ is a psychometrically appropriate assessment tool to evaluate meaningful differences in the reasons individuals use alcohol by itself and in combination with marijuana.