Date of Award


Publication Type

Doctoral Thesis

Degree Name





neuroenhancement, non-medical use of prescription stimulants, self-control, university students


Miller, Carlin




Students’ use of substances with the intent to enhance cognitive and/or academic functioning (referred to as “neuroenhancement”) has received increased academic attention in recent years. However, additional research regarding individual differences that increase risk of engagement in neuroenhancement is needed. Across three studies (total N = 410), the current dissertation sought to broaden the extant work in this area by investigating one candidate mechanism for university students’ engagement in neuroenhancement: self-control. In Study 1, associations of lifetime engagement in various modes of neuroenhancement (e.g., “legal neuroenhancement” using legal substances such as caffeine, over-the-counter substances, and nicotine; neuroenhancement using illicit drugs; and neuroenhancement via non-medical use of prescription stimulants [NMUPS] and other prescription drugs) with trait self-control (as measured via a multi-method approach) were investigated. Results demonstrated an association of self-control with neuroenhancement broadly, but demonstrated a differential pattern of associations of multivariate self-control across the various modes of neuroenhancement. Thus, this study highlighted poor self-control as an important characteristic of students who engage in neuroenhancement broadly and emphasized the importance of differentiating substance-specific classes of neuroenhancement. Study 2 sought to investigate the impacts of state self-control depletion on neuroenhancement outcomes (i.e., willingness to engage in neuroenhancement, self-reported likelihood of future engagement in neuroenhancement behaviour). Participants were randomly-assigned to complete either a purportedly “self-control-depleting” or non-depleting condition of a well-established experimental paradigm (Baumeister et al., 1998). Although trait self-control was inversely related to intent to engage in neuroenhancement, the study failed to demonstrate an effect of state self-control depletion on neuroenhancement (operationalized as attitudes and future neuroenhancement intent). Finally, Study 3 investigated self-control as a potential contributing factor to the previously-demonstrated association of poor academic functioning with engagement in NMUPS. As a secondary aim, this study also compared this association across NMUPS history variables derived across two time-frames (i.e., dichotomous coding of lifetime and past 30-day history of NMUPS) and two measurement methods (i.e., 30-day NMUPS history, as measured via a single question vs. through an adapted timeline follow-back approach). Although the pattern of associations varied across models, self-control and GPA both contributed to the statistical prediction of neuroenhancement history. In the case of past 30-day history (measured dichotomously), associations of GPA with neuroenhancement were fully accounted for by self-control. Interestingly, timeline follow-back measurement of NMUPS was associated with neither GPA nor the self-control variables. Across these three studies, variations in self-control were demonstrated to be associated with students’ engagement in substance use for cognitive enhancement purposes. Findings are discussed in the context of the Drug Instrumentalization Theory (Mueller & Schumann, 2011) and existing models of neuroenhancement as a behaviour aimed at self-medication of undiagnosed or subclinical cognitive symptoms (e.g., inattention). Implications for assessment of neuroenhancement are also discussed.