Date of Graduation


Document Type


Degree Name

Doctor of Philosophy in Psychology (PhD)

Degree Level



Psychological Science


Lindsay S. Ham

Committee Member

Matthew T. Feldner

Second Committee Member

Ellen Leen-Feldner


Psychology, Health and environmental sciences, Drug use, Emerging adults, Motives, Nonmedical prescription drug use, Substance use


The prevalence of nonmedical prescription drug (NMPD) use continues to increase among emerging adult populations; however, little is known about the motivations behind this use. The current study aimed to extend previous research by developing and validating the first known comprehensive NMPD motives measure. As such, the primary focus of the current study was to examine evidence for the reliability and validity of the NMPD Motives Questionnaire by assessing the factor structure, internal consistency, and construct validity of the motives scale. Participants were drawn from a larger study of college student substance use behaviors and attitudes (N = 1,427; Mage= 19.8; 65% female; 48.5% White Non-Hispanic) from two public universities in the United States. From the larger sample, 423 individuals (Mage= 19.9; 62% female; 53% White Non-Hispanic) reported lifetime NMPD use and thus were included in the final study sample. Participants completed online self-report questionnaires, including the NMPD Motives Questionnaire. Following data reduction procedures, the final measure included 20-items in which respondents indicated reasons they use NMPDs on a scale of 1 (Almost Never/Never) to 5 (Almost Always/Always). Exploratory factor analyses revealed a four-factor model of NMPD motives; including: Social/recreation, performance, conformity, and self-medication. Results of the current study suggest the overall scale and each of the four subscales of the NMPD Motives Questionnaire demonstrate good to excellent internal consistency, providing evidence for reliability. Moreover, results also suggest strong convergent, discriminant, and concurrent validity of the developed NMPD motives measure. Similar to patterns observed for other types of substance use, Social/recreation, performance, and self-medication motives for NMPD use were found to be significant positive predictors of the frequency of past 6-month NMPD use, after controlling for relevant covariates. Moreover, findings suggest self-medication NMPD motives significantly predict NMPD-related problems after controlling for use. These findings support incremental validity of the developed measure. Taken together, results of this study support the NMPD Motives Questionnaire as a potentially psychometrically sound instrument for measuring motives for NMPD use.