The Impact of Legalizing and Regulating Weed: Issues with Study Design and Emerging Findings in the USA.

Evaluations of the impact of medical and recreational marijuana laws rely on quasi- or natural experiments in which researchers exploit changes in the law and attempt to determine the impact of these changes on outcomes. This chapter reviews three key issues of causal inference in observational studies with respect to estimating of impact of medical or recreational laws on marijuana use-intervention definition, outcome measurement, and random assignment of study participants. We show that studies tend to use the same statistical approach (differences-in-differences) and yet find differential impacts of medical marijuana laws on adult use in particular. We demonstrate that these seemingly conflicting findings may be due to different years of analysis, ages of the study sample in each year, and assignment of jurisdictions to the control group versus treatment group.

Continuous quality improvement (CQI) in addiction treatment settings: design and intervention protocol of a group randomized pilot study.

BACKGROUND: Few studies have designed and tested the use of continuous quality improvement approaches in community based substance use treatment settings. Little is known about the feasibility, costs, efficacy, and sustainment of such approaches in these settings. METHODS/DESIGN: A group-randomized trial using a modified stepped wedge design is being used. In the first phase of the study, eight programs, stratified by modality (residential, outpatient) are being randomly assigned to the intervention or control condition. In the second phase, the initially assigned control programs are receiving the intervention to gain additional information about feasibility while sustainment is being studied among the programs initially assigned to the intervention. DISCUSSION: By using this design in a pilot study, we help inform the field about the feasibility, costs, efficacy and sustainment of the intervention. Determining information at the pilot stage about costs and sustainment provides value for designing future studies and implementation strategies with the goal to reduce the time between intervention development and translation to real world practice settings.