| LEVEL | SOURCE OF EVIDENCE |
| Ia | Evidence obtained from meta-analysis or systematic reviews of randomized controlled trials and/or synthesis of multiple studies primarily of quantitative research. |
| Ib | Evidence obtained from at least one randomized controlled trial. |
| IIa | Evidence obtained from at least one well-designed controlled study without randomization. |
| IIb | Evidence obtained from at least one other type of well-designed quasi-experimental study, without randomization. |
| III | Evidence obtained from the synthesis of multiple studies primarily of qualitative research. |
| IV | Evidence obtained from well-designed non-experimental observational studies, such as analytical studies or descriptive studies, and/or qualitative studies. |
| V | Evidence obtained from expert opinion or committee reports, and/or clinical experiences of respected authorities. |
Addiction and Mental Health
Integrating Tobacco Interventions into Daily Practice
Practice Recommendations