Cannabis does not affect respiration

Posted 31 January 2023

A new study shows that cannabis, and in particular the THC component, has no effect on the breathing system. The Leiden University Medical Center (LUMC) has conducted research into this. The outcome is important safety information when using cannabis for medical purposes.

There is not much knowledge on the effect of cannabis on ventilatory control – the unconscious and automatic process of breathing. The clinical study at the LUMC administered vaporized Bedrocan® to 18 volunteers to study the effect of THC on breathing with and without the addition of an opioid. Since opioids can potentially cause life-threatening respiratory depression, it is important to understand if combining opioids with cannabinoids can intensify this problem. It is possible that such a combination of products will be used in the treatment of chronic pain. Fortunately, the results of the clinical trial suggests that THC has no effect on ventilatory control.

Below you can find the original abstract of the study, executed by the research team of professor dr Albert Dahan.

Inhaled Δ9-tetrahydrocannabinol (THC) is without effect on respiration and does not enhance oxycodone-induced respiratory depression: A randomized controlled trial in healthy volunteers

British Journal of Anaesthesia

Introduction: In humans, the effect of cannabis on ventilatory control is poorly studied and consequently the effect of D⁹-tetrahydrocannabinol (THC) remains unknown, particularly when THC is combined with an opioid. We studied the effect of THC on breathing without and with oxycodone pretreatment. We expect that THC causes respiratory depression, which is amplified when THC and oxycodone are combined.

Methods: In this randomized controlled trial, healthy volunteers were treated with 100 mg inhaled Bedrocan^®, a pharmaceutical-grade high-THC cannabis variant, that contains 21.8% THC and 0.1% cannabidiol, following placebo or 20 mg oral oxycodone pretreatment; THC was inhaled 1.5 and 4.5-h after placebo or oxycodone intake. The main endpoint was isohypercapnic ventilation at an end-tidal PCO₂ of 55 mmHg (V̇_E55). V̇_E55 was measured at 1-h intervals for 7 hours following placebo/oxycodone intake.

Results: In 18 volunteers of either sex, oxycodone produced a 30% decrease in V̇_E55, while placebo was without effect on V̇_E55. The first cannabis inhalation changed V̇_E55 from 20.3 (3.1) to 23.8 (2.4) L min^-1 (p = 0.06) after placebo and from 11.8 (2.8) to 13.0 (3.9) L min^-1 (p = 0.83) after oxycodone pretreatment. The second cannabis inhalation had similarly no effect on V̇_E55 (placebo/THC p = 0.94; oxycodone/THC p = 0.99).

Conclusions: In humans, THC has no effect on ventilatory control following placebo or oxycodone pretreatment. This suggests that CB receptors do not act at human respiratory neuronal pathways in the brainstem, or that cannabinoid type 1 receptor-induced respiratory depression is offset by an opposing effect at cannabinoid type 2 receptors.

Read outcome study

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