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Which Cannabis Delivery Method is More Potent: Vaping or Smoking?

March 15, 2021 in General Education

Many cannabis consumers would agree that vaping provides stronger effects than smoking. That is because vaping is a much more efficient THC delivery method. Until recently, only anecdotal evidence was available to substantiate this claim. Now, thanks to a recent study, there is scientific evidence to corroborate it by quantifying the different effects between the two delivery methods. In this article, I will cite the Johns Hopkins Medicine study, describing the methodology, the results, the limitations, and the implications.

Study: Vaping Cannabis Produces Stronger Effects Than Smoking Cannabis For Infrequent Users

The study was conducted from June 2016 to January 2017 by researchers at Johns Hopkins Bayview Medical Center’s behavioral pharmacology research unit. The results were published in the November 30, 2018 Edition of The Journal of the American Medical Association (JAMA) Network Open.

Study Methodology

The study participants consisted of nine men and eight women with an average age of 27.3 years who had not consumed any cannabis for an average of 13 months prior to the study. They were prescreened for cannabis and other drugs to confirm this.

Each participant consumed six doses; three vaped from a vaporizer and three smoked from preloaded pipes containing the following:

  • 10mg THC
  • 25mg THC
  • 0 THC Placebo

The time frame for the study was a single visit once a week for six weeks. It was a double-blind study where neither the participants nor the researchers knew which doses the participants received in any session.

Assessments

During each session, the research team observed and assessed the effects of the drug, including any adverse reactions by:

  • Measuring vital signs such as heart rate and blood pressure
  • Collecting blood samples immediately after smoking, every 30 minutes for two hours and then hourly for eight hours

Measuring The Effects of Cannabis

In order to quantify the effects between the two cannabis delivery methods, the following tasks were administered:

  • The Drug Effect Questionnaire along with three computerized tasks
  • The Digit Symbol Substitution Task (DSST)
    This test evaluates cognition. Participants use paper and pencil on a sheet of paper that requires them to employ a key located at the top of the page to match symbols to numbers. The score is determined by the number of correct responses within the allotted time of 90-120 seconds.
  • The Divided Attention Task
  • Paced Auditory Serial Addition Task (PASAT)
    This test was originally developed to assess the effects of Traumatic Brain Injury (TBI) on cognitive function. It tests memory, attention and mathematical ability. Participants are given a number every 2-3 seconds, depending on the version, and tasked with adding the number they just heard with the number they heard just before it.

Drug Effect Questionnaire

Each participants filled out the Drug Effect Questionnaire, a self-reporting rating of the effects of a drug, using a total score of 100 points.  The effects included the following: Sick, Anxious, Hungry, Sleepy, Restless, Racing Heart, Dry Mouth, Dry Eyes, Cough and Memory Impairment. Assessments were taken a short time after smoking and then hourly for up to eight hours.

Results of Dosing 25mg THC

  • Vapers of the 25mg dose reported an average score of 77.5 to describe the psychotropic effects of the drug compared to 66.4 for smokers
  • Vapers reported an average higher score of 7% for anxiety and paranoia compared to smokers
  • Vapers reported an average score of 67.1 for dry mouth compared to 42.6 for smokers
  • Vapers reported an average higher score for dry eyes compared to smokers

Results of Computerized Tasks

Participants completed three computerized tasks which measured their memory, attention span, motor movement and physiological reaction time. The tests were designed to mimic the necessary skills for acceptable workplace performance, driving a vehicle and other normal activities. Reaction times were slower by more than 0.12 seconds with both doses for vapers and smokers when compared to the placebo.

Divided Attention Task

This test requires participants to follow a square on a computer screen while simultaneously monitoring numbers located in each corner of the screen.

  • There was a 170% average decrease in the amount of time that smokers of the 25mg dose were able to accurately track the square compared to those who smoked the placebo.
  • There was a 350% average decrease in the amount of time that vapers of the 10mg dose were able to accurately track the square compared with smokers of the same dose.
  • There was a 500% average decrease in the amount of time that vapers of the 25mg dose were able to accurately track the square compared with smokers of the same dose.

Blood Level Results

THC blood levels were at their highest immediately after smoking or vaping cannabis.

  • Vapers of the 10mg dose recorded an average THC blood level of 7.5 nanograms/ml and at 25mg a blood level of 14.4 nanograms/ml within ten minutes of inhalation
  • Smokers of the 10mg dose recorded an average THC blood level of 3.8 nanograms/ml and at 25mg a blood level of 10.2 nanograms/ml within ten minutes of inhalation

Notable Adverse Reactions

  • Two participants vomited and one participant experienced hallucinations after vaping 25 mg of THC
  • One participant vomited after smoking 25mg THC

Study Limitations

  • THC blood levels were detected for up to 4 hours after usage despite reports by participants that the effects of the THC lasted 5-6 hours. This indicates that using a blood test to determine impairment is not an accurate tool.
  • Results were based only on short-term usage by infrequent consumers. Long-term usage data on vaping must be collected before making a definitive assessment of the effects of vaping vs smoking.
  • Results could not be extrapolated for regular consumers with a high tolerance for THC
  • Only three doses using one cannabis strain low in CBD were used
  • Only flower was used for vaping; concentrates were excluded. Only one vaporizer type, the Volcano Medic, was used for vaping at the exclusion of any other vaping devices.
  • A small pipe was the only device used for smoking

Ramifications For Consumers

Infrequent users and particularly new medical cannabis patients need to err on the side of caution when they begin to vape cannabis products. It is important to note that many of the products available at dispensaries have much higher THC percentages than those used in this research.

The study authors were surprised that there was such a large difference of impairment between vaping vs smoking using equal doses. The researchers acknowledge that more research is needed to investigate if the same effects would be achieved using other types of vaporizing and smoking methods. Such data is crucial for providing more informed dosing guidelines, cannabis policy and regulation and to develop ways to detect cannabis intoxication.

Sources:
leafly.com, Which Is More Potent, Vaping Cannabis or Smoking a Joint? Ryan Basen, Jan. 28, 2019
sciencedaily.com, Vaping Cannabis Produces Stronger Effects Than Smoking Cannabis For Infrequent Users, Johns Hopkins Medicine, Dec. 4, 2018
pubmed.ncbi.nlm.nih.gov/16290063/A Comprehensive Review of the Paced Auditory Serial Addition Test (PASAT), Nov. 4, 2005

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