Applying an Extended Version of the Theory of Planned Behavior to Illicit Drug Use Among Students1
Journal of Applied Social Psychology August 1, 2003 DOI: 10.1111/j.1559-1816.2003.tb01968.x (opens in new tab) via OpenAlex
Summary
AI-generated from the abstractThe theory of planned behavior (TPB) predicted intentions to use and actual use of LSD, amphetamine, cannabis, and ecstasy over six months among 461 students. The TPB explained about 49% of the variance in intentions and 45% in behavior. Descriptive norms added to the prediction of intentions for all four drugs, while moral norms further predicted cannabis intentions. Attitude variability weakened or strengthened the link between attitudes and intentions for LSD and ecstasy. Attitudes also influenced how strongly perceived behavioral control affected intentions for all drugs. Perceived behavioral control moderated the intention-behavior link for each drug, showing that the TPB's relationships depend on other factors.
Study at a glance
| Characteristics | Observational cohort Peer reviewed |
|---|---|
| Sample size | 461 |
| Population | Students |
| Duration | 6-month follow-up |
| Keywords | Illicit drug Social psychology |
| Citations | 163 |
| Key finding | The theory of planned behavior predicted intentions and use of four illicit drugs over six months, with descriptive norms, moral norms, and interactions among attitudes, perceived behavioral control, and intentions revealing boundary conditions. |
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.