Do Delta9-tetrahydrocannabinol concentrations indicate recent use in chronic cannabis users?

Area of Science:

• Pharmacology and Toxicology
• Cannabinoid Research
• Forensic Science

Background:

• Chronic cannabis use leads to accumulation of Delta-9-tetrahydrocannabinol (THC) in the body.
• Understanding THC elimination kinetics is crucial for clinical and legal contexts.
• Previous studies have not fully quantified blood THC persistence during extended abstinence.

Purpose of the Study:

• To quantify blood Delta-9-tetrahydrocannabinol (THC) concentrations in chronic cannabis users.
• To assess THC persistence over a 7-day period of monitored abstinence.
• To investigate factors influencing THC elimination in heavy users.

Main Methods:

• Twenty-five frequent, long-term cannabis users were admitted to a research unit for continuous medical surveillance.
• Whole blood samples were collected over 7 days of monitored abstinence.
• Delta-9-tetrahydrocannabinol (THC) and its carboxy-metabolite concentrations were measured using two-dimensional gas chromatography-mass spectrometry.

Main Results:

• Nine participants (36%) had no measurable THC after 7 days of abstinence.
• Six participants still showed detectable THC concentrations on day 7 (mean +/- SD: 0.3 +/- 0.7 ng/ml).
• All 25 participants had measurable carboxy-metabolite levels on day 7 (mean +/- SD: 6.2 +/- 8.8 ng/ml).

Conclusions:

• Substantial whole blood Delta-9-tetrahydrocannabinol (THC) concentrations persist for multiple days after discontinuation in heavy chronic cannabis users.
• The neurocognitive effects of low, persistent THC concentrations and their relation to performance recovery remain unknown.
• Findings have implications for implementing per se limits in driving under the influence of drugs legislation.