Evidence from European and American studies indicate that the construct motivational structure is an important predictor of substance use. For the first time, the current study (a) tested and compared the power of motivational structure in predicting substance use among Iranian (N= 126) and alcohol use among British students (N = 96); and (b) tested the mediating role of motivational structure in carrying the effects of sense of control onto substance use. Participants completed The Personal Concerns Inventory, The Shapiro Control Inventory, the Aspirations Index, and the Alcohol/Substance Use Questionnaire. Iranians students completed two additional scales: the CES-Depression and The Satisfaction with Life Scale mainly to help validate the researcher-compiled Persian Substance Use Questionnaire and the Persian-PCI. Correlational and mediational analyses were conducted to test the study hypotheses across the two samples. First, the results supported the reliability and validity of Persian versions of the PCI and the Substance Use Questionnaire. Second, across both samples, sense of control was positively correlated with intrinsic motivation, adaptive motivational structure, and satisfaction with life, but it was negatively related with extrinsic motivation (but not in the Iranian sample), depression, and substance/alcohol use. Third, for both samples, the PCI adaptive motivation was positively correlated with sense of control, and intrinsic motivation, and negatively correlated with alcohol and substance use. Forth, across both samples, the PCI adaptive motivation mediated the relationship between sense of control and substance/alcohol use. In conclusion, the PCI motivational structure was an important construct in predicting the use of unprescribed substances regardless of the cultural diversity of the participants. The implications of sense of control and motivational structure for both theory and practice will be discussed.

Evidence from European and American studies indicate that the construct motivational structure is an important predictor of substance use. For the first time, the current study (a) tested and compared the power of motivational structure in predicting substance use among Iranian (N= 126) and alcohol use among British students (N = 96); and (b) tested the mediating role of motivational structure in carrying the effects of sense of control onto substance use. Participants completed The Personal Concerns Inventory, The Shapiro Control Inventory, the Aspirations Index, and the Alcohol/Substance Use Questionnaire. Iranians students completed two additional scales: the CES-Depression and The Satisfaction with Life Scale mainly to help validate the researcher-compiled Persian Substance Use Questionnaire and the Persian-PCI. Correlational and mediational analyses were conducted to test the study hypotheses across the two samples. First, the results supported the reliability and validity of Persian versions of the PCI and the Substance Use Questionnaire. Second, across both samples, sense of control was positively correlated with intrinsic motivation, adaptive motivational structure, and satisfaction with life, but it was negatively related with extrinsic motivation (but not in the Iranian sample), depression, and substance/alcohol use. Third, for both samples, the PCI adaptive motivation was positively correlated with sense of control, and intrinsic motivation, and negatively correlated with alcohol and substance use. Forth, across both samples, the PCI adaptive motivation mediated the relationship between sense of control and substance/alcohol use. In conclusion, the PCI motivational structure was an important construct in predicting the use of unprescribed substances regardless of the cultural diversity of the participants. The implications of sense of control and motivational structure for both theory and practice will be discussed.

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