The purpose of this study is to better understand how high-potency cannabis products, such as concentrates (including hashish, oils, and butters), may affect mental health, mood, thinking, and daily functioning. Researchers also hope to learn how THC levels measured in blood relate to mental health outcomes by comparing people who use concentrates, those who use less potent cannabis products like flower, and those who do not currently use cannabis.

You may be eligible for this study if you meet the following criteria.

Inclusion Criteria:

• Must be a twin
• Ages 21-48
• Have not experienced a traumatic brain injury
• Use cannabis regularly
• Consent to other twin knowing about cannabis use and are enrolled

Researcher name: Soo Rhee, Ph.D.
Contact information: Concentratestudy@colorado.edu 
Title of study: Effects of high potency cannabis products on mental health and psychosocial functioning
Time commitment: 3 visits every 6 months for 1 year (4.5 hours total)
CU Boulder IRB approval #23-0187

If you qualify and choose to participate:

1. Complete a phone screening with the research team to confirm your eligibility.
2. Participate in three Zoom study visits over approximately one year, with visits scheduled about six months apart.

During each 1.5-hour Zoom visit, you will:

1. Answer questions about your cannabis use and health.
2. Complete online surveys about your personality, mood, and relationships.
3. Complete online thinking and cognitive tasks.
4. Collect a small finger-prick blood sample using a kit mailed to your home, with guidance from a researcher during the Zoom visit.
5. Mail your blood sample back to the study team using the prepaid shipping materials provided.
6. Beginning about one week before your second study visit, complete brief daily surveys about your cannabis use through a smartphone app, text message, or email.

Participants will receive $100 by check after each completed study visit, plus $5 for each completed Daily Diary survey. Participants who complete all study activities may receive up to $370 total.

All study visits are conducted remotely over Zoom, so no travel is required.

There is no cost for you to participate in our research study.