Applying an Extended Version of the Theory of Planned Behavior to Illicit Drug Use Among Students1
Journal of Applied Social Psychology – August 01, 2003
Source: OpenAlex
Summary
Intentions to use illicit drugs like LSD, amphetamine, cannabis, and ecstasy can be predicted effectively using the theory of planned behavior. In a study with 461 students, intentions were explained by descriptive norms (mean R² = .49) and moral norms specifically for cannabis. Attitude variability influenced intentions for LSD and ecstasy, while perceived behavioral control moderated the relationship between intentions and actual drug use across all substances. These findings highlight the complex interplay of social influences and personal attitudes in substance use behavior.
Abstract
This study employed the theory of planned behavior (TPB) to investigate the factors underlying intentions to use and use of LSD, amphetamine, cannabis, and ecstasy over 6 months in a sample of students ( N = 461). The TPB provided good predictions of both intentions (mean R 2 = .49) and behavior (mean R 2 = .45). Descriptive norms explained additional variance in intentions for all the drugs, and moral norms explained additional variance in cannabis intentions. Attitude variability moderated the impact of attitudes on intentions for LSD ( p < .10) and ecstasy ( p < .05). Attitude moderated the impact of perceived behavioral control (PBC) on intentions for all drugs ( p < .001). PBC moderated the impact of intentions on behavior for LSD ( p < .05), amphetamine ( p < .10), cannabis ( p < .05), and ecstasy ( p < .10). These interaction effects elucidate limiting conditions among the variables in the TPB.