What Happens When You Combine ADHD Medication with THC
Combining oral THC with methylphenidate (Ritalin) produced additive increases in heart rate and unique subjective effects, while THC impaired attention and MPH partially offset some cognitive effects.
Quick Facts
What This Study Found
In a double-blind crossover experiment, 16 healthy adults received all combinations of placebo or 10mg THC with 0mg, 10mg, or 40mg methylphenidate (MPH) across six sessions.
The two drugs showed additive effects on heart rate: peak heart rate climbed from 89 beats per minute with THC alone to 96 with low-dose MPH added and 102 with high-dose MPH. Significant interactions appeared on subjective measures of "Feel Drug," "Good Effects," and "Take Drug Again."
THC increased commission errors on attention tasks, while MPH reduced reaction time variability. On a working memory task, MPH decreased reaction times but THC partially reversed those gains.
Key Numbers
16 participants; 6 sessions each; peak HR with 10mg THC + 40mg MPH: 102 bpm vs. 89 bpm with THC alone; significant THC x MPH interactions on three subjective measures
How They Did This
Randomized, double-blind, crossover design with 16 healthy adults. Six sessions tested all combinations of THC (0 or 10mg oral) and MPH (0, 10, or 40mg oral). Sessions separated by at least 48 hours. Measured vital signs, subjective drug effects, continuous performance test, and n-back working memory task.
Why This Research Matters
Young adults commonly combine marijuana with illicit stimulant use. This is one of the first controlled studies examining what happens physiologically and cognitively when these substances interact, revealing potentially concerning cardiovascular effects.
The Bigger Picture
As both cannabis use and stimulant medication/misuse are common among young adults, understanding their combined effects is important for clinical guidance and harm reduction. The additive cardiovascular effects are a particular concern.
What This Study Doesn't Tell Us
Very small sample (n=16). Participants were healthy adults without ADHD, so findings may not apply to those with the condition. Used low-moderate doses that may not reflect real-world use patterns. Single oral THC dose does not replicate smoking.
Questions This Raises
- ?Are the additive cardiovascular effects clinically dangerous at higher doses?
- ?How does this combination affect people with ADHD, who process stimulants differently?
- ?Would chronic co-use produce tolerance to the cardiovascular effects?
Trust & Context
- Key Stat:
- Heart rate: 89 bpm (THC alone) to 102 bpm (THC + high-dose MPH)
- Evidence Grade:
- Rigorous crossover RCT design but very small sample size (n=16) and limited to healthy non-ADHD participants.
- Study Age:
- Published in 2015. Cannabis potency and stimulant prescribing patterns have both changed.
- Original Title:
- An exploratory study of the combined effects of orally administered methylphenidate and delta-9-tetrahydrocannabinol (THC) on cardiovascular function, subjective effects, and performance in healthy adults.
- Published In:
- Journal of substance abuse treatment, 48(1), 96-103 (2015)
- Authors:
- Kollins, Scott H(6), Schoenfelder, Erin N, English, Joseph S, Holdaway, Alex, Van Voorhees, Elizabeth, O'Brien, Benjamin R, Dew, Rachel, Chrisman, Allan K
- Database ID:
- RTHC-00993
Evidence Hierarchy
Participants are randomly assigned to treatment or placebo groups to test cause and effect.
What do these levels mean? →Frequently Asked Questions
Is it dangerous to use cannabis with ADHD medication?
This study found additive increases in heart rate when THC and methylphenidate were combined, suggesting increased cardiovascular strain. The clinical significance at typical doses is not fully established, but the combination warrants caution.
Did THC cancel out the focus benefits of Ritalin?
Partially. THC increased attention errors and reduced some of the cognitive improvements from methylphenidate, particularly on working memory tasks.
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Cite This Study
https://rethinkthc.com/research/RTHC-00993APA
Kollins, Scott H; Schoenfelder, Erin N; English, Joseph S; Holdaway, Alex; Van Voorhees, Elizabeth; O'Brien, Benjamin R; Dew, Rachel; Chrisman, Allan K. (2015). An exploratory study of the combined effects of orally administered methylphenidate and delta-9-tetrahydrocannabinol (THC) on cardiovascular function, subjective effects, and performance in healthy adults.. Journal of substance abuse treatment, 48(1), 96-103. https://doi.org/10.1016/j.jsat.2014.07.014
MLA
Kollins, Scott H, et al. "An exploratory study of the combined effects of orally administered methylphenidate and delta-9-tetrahydrocannabinol (THC) on cardiovascular function, subjective effects, and performance in healthy adults.." Journal of substance abuse treatment, 2015. https://doi.org/10.1016/j.jsat.2014.07.014
RethinkTHC
RethinkTHC Research Database. "An exploratory study of the combined effects of orally admin..." RTHC-00993. Retrieved from https://rethinkthc.com/research/kollins-2015-an-exploratory-study-of
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.