Utility of the theory of planned behavior for adolescent alcohol, tobacco, and other drug prevention behavior

Background: Adolescent alcohol, tobacco, and other drug (ATOD) use is a serious public health problem and associated with accidental death, homicide, suicide, sexually transmitted diseases, and teen pregnancy. Prevention of ATOD must begin in the teen years because habitual use at a young age results in a stronger addiction that is more difficult to quit. Measures to assess adolescents' beliefs about ATOD use were needed to evaluate Operation Snowball (OS), an ATOD prevention program to encourage responsible decisions and understand one's self and motivations when making decisions about ATOD use. Purpose: This descriptive study used Ajzen's (1985) methodology to develop and test measures for Theory of Planned Behavior (TPB) constructs—behavioral beliefs, normative beliefs, control beliefs, attitudes, subjective norm, perceived control, intentions to not use ATOD, and ATOD behaviors. Results: There were 300 OS participants at pre-test and 204 (68%) at one-year post-test. Post-test participants were mostly female (75%), White (89.0%), and in grades 6 to 9. A 62-item instrument based on TPB constructs relevant to ATOD behavior were used at pre- and post-test to assess reliability and validity. Pre-test scale Cronbach's alpha reliabilities were acceptable for behavioral beliefs (.83), normative beliefs (.94), control beliefs (.81), attitude (.95), perceived behavioral control (.72), intentions (.83), and ATOD behaviors (.80), and less acceptable for subjective norm (.69) with a scale of 3 items. Scale item correlations with scale totals were at least .40 for all measures. Similar scale reliabilities were observed at post-test. For both pre- and post-test data, Baseline TPB model fit was modest, but all TPB path coefficients were significant except for a path between subjective norm and intention. A modified model, at both pre- and post-test, with additional paths among TPB constructs produced an excellent fit (Bentler's CFI = .99), but added to model complexity. Conclusions: There is evidence that the TPB scales are valid and reliable for use with adolescents in the OS program and that a theory-based assessment of an ATOD prevention program is viable. Future research should compare change in TPB measures as adolescents advance in future OS prevention interventions.