2026 Discovery Award Nominee: Julie K. Johnson, PhD

Julie K. Johnson, PhD, has spent nearly two decades advancing cannabis policy and public health research, including eight years as the inaugural Chief of Research at the Massachusetts Cannabis Control Commission. Her work examines some of the most consequential questions surrounding cannabis legalization, including youth prevention, impaired driving, product safety, and regulatory oversight. Throughout her career, Johnson has used rigorous research and large-scale data to identify which public health concerns the evidence supports and how cannabis policies can better protect patients and the public.

One defining feature of Johnson's work is her willingness to challenge her own hypotheses when the evidence points elsewhere. Preventing youth substance use is deeply personal to her, and she initially anticipated that medical cannabis legalization would increase adolescent cannabis use. However, a study she coauthored examining more than one million adolescents across 46 states found that medical marijuana laws and dispensary provisions were not associated with increased adolescent cannabis use or heavy use during the study period. Rather than defend her original expectations, Johnson used those findings to advance prevention strategies grounded in measurable risks, including research into how retail-density limits and other regulatory safeguards can be incorporated into legalization policies.

Her research has also confronted the longstanding challenge of distinguishing cannabis use from actual impairment. Johnson has highlighted the limitations of blood, urine, and oral fluid tests, which can detect THC or its metabolites without establishing whether someone is currently impaired. Her work calls for better impairment research, stronger data collection, law enforcement training, and public education to improve roadway safety while addressing the limitations of existing testing approaches.

Johnson has also demonstrated how regulatory data can expose weaknesses in cannabis product safety systems. An analysis of more than 120,000 Massachusetts cannabis laboratory testing results from 2021 through 2023 examined potency trends, microbial contamination, and laboratory compliance data. The findings included yeast and mold failures in approximately 9% of samples and anomalies that raised questions about testing reliability and reporting practices. Johnson has advocated for stronger data systems and regulatory monitoring to identify potential problems, improve accountability, and help ensure patients and consumers receive products that are accurately tested and labeled.

Her research also examines how states can protect medical cannabis programs as adult-use markets expand. In a 2023 study comparing Colorado, Oregon, and Massachusetts, Johnson and her coauthors found that medical patient registrations declined in Colorado and Oregon following the introduction of adult-use retail sales but increased in Massachusetts. The findings highlight how differences in state policies can influence the sustainability of medical cannabis programs and the importance of protecting patients' continued access as legalization evolves.

Beyond her own research, Johnson has worked to connect academic science with policymaking through professional publications, international scientific collaborations, and research advising. Her contributions reflect a sustained commitment to ensuring that cannabis regulations evolve alongside the evidence, allowing policymakers to respond to documented risks, reconsider unsupported assumptions, and identify where additional research is needed.

Julie K. Johnson's work exemplifies the Discovery Award by demonstrating how scientific integrity, methodological rigor, and the willingness to challenge established assumptions can strengthen cannabis safety. Her research provides policymakers with practical evidence to improve youth prevention, impaired-driving policies, product testing, and medical cannabis program sustainability while keeping public health and patient protections at the center of cannabis reform.

Selected Research & Publications

Medical Cannabis Program Sustainability in the Era of Recreational Cannabis (2023)
Clinical Therapeutics
Colby AM, Dilley JA, Pensky HM, Johnson JK.
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Medical Marijuana Laws and Dispensary Provisions Not Associated With Higher Odds of Adolescent Marijuana or Heavy Marijuana Use: A 46-State Analysis, 1991–2015 (2021)
Substance Abuse
Johnson JK, et al.
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Building Evidence-Based Prevention Mechanisms Into Cannabis Legalization Policy and Regulations (2019)
American Journal of Public Health
Johnson JK, Doonan SM.
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A Baseline Review and Assessment of Cannabis Use and Public Safety, Part 1: Operating Under the Influence of Cannabis (2019)
Massachusetts Cannabis Control Commission
Read the report (PDF)

Cannabis Control Commission Industry Report: Adult- and Medical-Use Cannabis Markets (2025)
Massachusetts Cannabis Control Commission
Read the report overview and testing findings

A Research Agenda to Inform Cannabis Regulation: How Science Can Shape Policy (2023)
Clinical Therapeutics
Schauer GL, Johnson JK, et al.
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Learn more about Julie K. Johnson: Cannabis Control Commission research