Background and objectives <p>Cannabinoid treatments are commonly used for sleep conditions, but the direct sedating effects of daytime treatment consumption and indirect effects on night-time sleep are unclear. This study measures the direct effects of low-dose cannabinoid treatments on daytime sleepiness and potential indirect night-time sleep effects in healthy adult, novice cannabis users.</p> Methods <p>Using a double-blind, randomised, placebo-controlled cross-over design, participants were orally administered a standardised dose of 1 mL oil containing THC:CBD ratios of either 1:1, 1:16 or a placebo over five weekly in-lab visits. Daytime sleepiness was measured at 40, 135 and 265 min post-dosing using the Karolinska Sleepiness Scale (KSS). Indirect night-time sleep effects on total sleep time (TST), sleep-onset latency (SOL), and number of awakenings after onset were measured using daily wrist-actigraphy and sleep-diary entries during the 7-day washout period between treatments.</p> Results <p>Final analyses (N&#xa0;=&#xa0;20) showed subjective sleepiness (KSS score) significantly increased (mean difference&#xa0;=&#xa0;1.9, SE 0.25) from 40 min to 265 min post-treatment (<i>p</i>&#xa0;&lt;&#xa0;0.001). No significant differences were observed between treatments for KSS. Indirect sleep measures (TST, SOL, number of awakenings) showed no differences between treatments or over time (all <i>p</i>&#xa0;&gt;&#xa0;0.05).</p> Conclusion <p>Daytime consumption of low-dose cannabinoid oils did not induce direct sleepiness or indirect night-time effects post-dosing among adults. Future studies would benefit from exploring pharmacokinetics and the possibility of treatment amplification of daytime fatigue, mood and cognitive changes to assist the development of therapeutic guidelines for safe daytime medical cannabis use.</p> ANCTR Trial Registration Number <p>ACTRN12622001539729, 13 December 2022, prospectively registered.</p>