Addictions, Drug & Alcohol Institute

High-THC Concentration Cannabis

With a legal market of cannabis products has come the wide distribution of manufactured products containing much higher levels of THC than what has been historically found in the plant.

Science to date shows a dose-response relationship between THC concentration and health consequences. Manufactured cannabis products may add further risks due to additives, residues and contaminants.

Researchers and policy makers are working to better understand these risks. This page contains recent reports and summaries that describe what we know so far.

Cannabis Concentration and Health Risks: A Report for the Washington State Prevention Research Subcommittee

logo from potency report

This consensus statement and report, published in November 2020, was developed by a workgroup of research scientists from the University of Washington (UW) and Washington State University (WSU) with the intent of providing policy makers with a summary of the current evidence on topics of public health importance related to cannabis concentration.

Download the report and additional resources:

Workgroup members include:

  • Beatriz Carlini, PhD, MPH, UW, Addictions, Drug & Alcohol Institute (Chair)
  • Celestina Barbosa-Leiker, PhD, WSU, Health Sciences
  • Carrie Cuttler, PhD, WSU, Department of Psychology
  • Julia Dilley, PhD, MES, Multnomah County Health Department and State of Oregon Public Health Division
  • Caislin Firth, PhD, MPH, UW, Addictions, Drug & Alcohol Institute
  • Kevin Haggerty, PhD, MSW, UW, School of Social Work
  • Jason Kilmer, PhD, UW, Department of Psychiatry & Behavioral Sciences
  • Mike McDonell, PhD, MS, WSU, College of Medicine, Behavioral Health Innovations
  • Nephi Stella, PhD, UW, Departments of Pharmacology and Psychiatry & Behavioral Sciences
  • Denise Walker, PhD, UW, Innovative Programs Research Group
  • Dale Willits, PhD, WSU, Criminal Justice & Criminology
  • Liz Wilhelm, Prevention WINS

Additional Resources

Other groups have also worked to describe what we know so far about high-potency cannabis and the implications for public health and policy decisions. Links to these reports and summary statements can be found below.