Delta‐9‐Tetrahydrocannabinol ( THC ) Before Bedtime: Feasibility and Mechanistic Pilot Study on Sleep and Cardiac Autonomic Activity

ABSTRACT Disordered sleep is a common reason individuals report using cannabis, yet the physiological effects of Δ 9 ‐tetrahydrocannabinol (Δ 9 ‐THC) on sleep and autonomic regulation remain incompletely understood. Early studies reported acute sleep‐promoting effects of Δ 9 ‐THC, but chronic use has been associated with disrupted sleep and possible cardiovascular risk. This feasibility and mechanistic pilot study examined the influence of acute Δ 9 ‐THC administration on sleep and cardiac parasympathetic activity in adults with and without regular cannabis use. Nine individuals with regular cannabis use (> 3× per week) and nine individuals with minimal cannabis exposure (no use within the previous year and < 10 lifetime exposures) underwent 2 weeks of actigraphy‐verified sleep stabilisation before a three‐night, single‐blind laboratory protocol including an acclimatisation night, a placebo night, and a 10 mg oral Δ 9 ‐THC dosing night. During at‐home monitoring, individuals who regularly used cannabis (permitted ad libitum cannabis use) had shorter total sleep time and greater sleep disruption than the no cannabis use group ( p < 0.05). In laboratory polysomnography revealed that Δ 9 ‐THC increased sleep latency, slow wave sleep ( p < 0.05), EEG spectral power across frequency bands ( p < 0.05), and attenuated delta power dissipation in the first half of the night (DrugxSleephour, p < 0.05). Δ 9 ‐THC also markedly reduced heart rate variability across time‐ ( p < 0.01) and frequency‐domain ( p < 0.05) metrics. These findings demonstrate the feasibility and tolerability of controlled in‐laboratory Δ 9 ‐THC administration following sleep stabilisation among adults who regularly use cannabis and those with minimal exposure, and provide preliminary mechanistic evidence that acute Δ 9 ‐THC before bedtime increases cortical activation and reduces cardiac parasympathetic activity during sleep.