Characteristics of included studies
| Study | Underpinning theory | Design (goal) | Intervention | Comparison | Primary outcome | Secondary outcome(s) | Analysis sample | Follow-up (total time) (months) |
|---|---|---|---|---|---|---|---|---|
| Polansky et al 199925 | Decision theory | RCT (E) | PSA | Other | – | Intention to use; attitudes; knowledge and disposition to select socially appropriate responses | 312 | NA (NS) |
| Miller et al 200020 | Self-regulation theory | CBA (F) | PSA; printed | No intervention | Use of drugs (incl. cannabis and cocaine) | Risk perception; problems related to drug use | 1024 | 12 (18) |
| Palmgreen et al 200124 | Influence of sensation-seeking on drug use | ITS (F) | PSA | No intervention | Past 30-day use of marijuana | – | 6371 | NA (32) |
| Yzer et al 200326 | Theories of behavioural change: persuasion effects | RCT (E) | PSA | No intervention; other | – | Intention to use marijuana; attitude; perceptions about marijuana | 418 | NA (NS) |
| Slater et al 200610 | Social-ecological framework (norms and expectations influence drug use) | RCT (E) | PSA; printed | No intervention | Lifetime and past 30-day use of marijuana | – | 4216 | 24 (42) |
| Zhao et al 200627 | Normative beliefs | RCT (E) | PSA | No intervention | – | Intention to use; beliefs towards marijuana; social norms | 435 | NS (NS) |
| Hornik 200622 | Unclear | Cohort (F) | PSA; printed; internet | Lower exposure | Lifetime, past year, and past 30-day use of marijuana | Intention to use; attitudes and self-efficacy; perceptions and social norms | 8117 | 56 (58) |
| Scheier and Grenard 201023 | Social marketing | Cohort (F) | PSA; printed; internet | Lower exposure | Past 12-month cannabis intoxications | – | 2515 | NA (48) |
| Schwinn et al 201019 | Social learning theory | RCT (E) | Internet | No intervention | Past 30-day substance use | – | 236 | 6 (NS) |
| Lee et al 201028 | Readiness to change | RCT (E) | Internet | No intervention | Past 90-day use of marijuana | Intention to change marijuana use; consequences | 341 | 6 (NS) |
| Fang et al 201018 | Family-oriented | RCT (E) | Internet | No intervention | Past 30-day use of marijuana | Intention to use marijuana | 216 | 6.25 (16) |
| Newton et al 201011 | Social influence approach | RCT (E) | Internet | Other | Use of cannabis | Cannabis knowledge; attitudes; related harms | 724 | 12 (21) |
| Meth Project studies12–16 | Perception of risk and perception of social disapproval are correlated with drug consumption | 4 ITS and 1 CBA (F) | PSA; printed; internet | No intervention | Past 30-day use of methamphetamine | Attitudes on methamphetamine and other drugs; perceptions; information sources and advertising awareness; | 26 405 | NA (Colorado 26; Georgia 18; Hawaii 25; Idaho 40; Wyoming 34) |
| Slater et al 201121 | Autonomy and aspiration perceptions as mediators of marijuana use | RCT (E); Cohort (F) | PSA; printed | Lower exposure | Lifetime, past 90-day and past 30-day use of marijuana | Autonomy and aspiration inconsistent with marijuana use | 3236 | 24 (42) |
| Carpenter and Pechmann 20112 | Unclear; evaluated many heterogeneous mass-media campaigns | ITS (F) | PSA; printed; internet | Lower exposure | Past 30-day and lifetime use of marijuana | – | 130 245 | NA (36) |
CBA, controlled before and after; Cohort, prospective cohort; E, experimental/efficacy setting; F, field/effectiveness setting; ITS, interrupted time-series; Lower exposure, lower exposure to same intervention; NA, not applicable; NS, not specified; Other, other intervention or different combination of same intervention; PSA, public service announcement (eg, television/radio); RCT, randomised controlled trial.