Changes in cannabis laws not associated with decreased opioid prescriptions

1. In this synthetic control analysis, changes in medical cannabis laws were not found to have made a significant difference in the proportion of patients receiving prescriptions for opioids for noncancerous pain.

2. Medical cannabis laws were also not found to impact the proportion of patients receiving procedures to address their chronic pain.

Evidence Rating Level: 1 (Excellent)

Study Rundown: Despite changes to medical laws that permit the use of cannabis for treating chronic noncancerous pain, evidence for its effectiveness in the literature is mixed. To date, this is the first study that aims to understand the effect of these medical cannabis laws on the prescribed treatment patterns for chronic noncancerous pain. Using a nonexperimental augmented synthetic control study, this study compared 12 states in the United States with implemented medical cannabis laws, against 17 comparator states to evaluate this question amongst commercially insured adults with known diagnoses relating to chronic pain (such as arthritis, fibromyalgia, chronic low back pain, etc.). The results of the study found that there was no significant association between medical cannabis laws and treatment metrics of chronic noncancer pain. Although this study is limited by key assumptions within its design as well as generalizability to populations who are not commercially insured, it added to the body of literature towards understanding the possible associations between medical cannabis laws and patterns of practice. Future studies evaluating the possible associations between medical cannabis laws and other metrics of health outcomes may further shed light on its potential impacts.

Click to read the study in AIM

In-Depth [synthetic control analysis]: This study utilized an augmented synthetic control analysis of 29 American states to evaluate the impact of medical cannabis laws on treatment outcomes of chronic noncancer pain. The primary outcomes were derived using aggregate state data and included summary prescription measures of both opioid and non-opioid pain medications and treatments related to addressing noncancer pain such as procedures. Adult participants over 18 years old enrolled in commercial Medicare insurance between 2010 to 2022 with known diagnoses of chronic noncancer pain four years prior to the implementation of a medical cannabis law were included. Overall, 583,820 participants from 12 states with medical cannabis laws, and 17 comparison states, were included in the study. The primary results of the analysis found that implementation of medical cannabis laws had no significant associations with treatment patterns of chronic noncancerous pain, such as the proportion of patients receiving opioid or nonopioid pain medication, or pain procedures within the first three years of law implementation. A key limitation of the study is its dependence on the assumption of parallel counterfactual trends. Further, it cannot be generalized to populations beyond the scope of its inclusion criteria. It was also not possible to capture patient-level substitutions of pain prescription medications for cannabis, nor pain medications that either do not require or are not warranted by insurance. Despite these limitations, this nonexperimental study design added to the body of evidence for understanding the possible associations of medical cannabis laws on treatment patterns of chronic noncancer pain. In summary, the results of this study suggest that cannabis laws do not impact the treatment of noncancerous pain in the United States.

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