Cannabis
Overview
Cannabis is the most widely used illicit drug worldwide.
In Australia, 8.8% population used cannabis in the year prior to 2007, the highest proportion were in 18-19 year bracket with nearly one in five reporting recent use [1].
It is estimated that about 10% of people who ever use cannabis will become dependent at some time in their lives [2].
Demand for treatment for cannabis use disorder is increasing, with cannabis nominated as the primary drug of concern in 21.5% of all closed AOD treatment episodes in 2007/8 [3].
Effects, risks and harms
Acute effects occur within minutes after smoking cannabis, can last four to six hours and commonly include euphoria, relaxation, perceptual changes (e.g. colours appear brighter), tachycardia, impaired cognitive and psychomotor performance, reddening of conjunctivae, postural hypotension, increased appetite, and drowsiness.
Dysphoric reactions such as severe anxiety and panic, paranoia and psychosis have also been observed which are often dose-related and occur more commonly among naïve and psychologically vulnerable users.
Long-term, chronic cannabis use can result in enduring impairment of attention, memory and executive functioning; respiratory problems, tolerance and dependence [4].
Pharmacology
The cannabis plant contains 60 unique cannabinoids, among which is the primary psychoactive cannabinoid delta-9-tetrahydrocannabinol or D-9 THC.
Humans have endogenous cannabinoid receptors (CB1 & CB2) that interact with endogenous cannabinoids (anandamide) and are present in areas of the brain, thought to be involved in a range of functions including: cognition, memory, anxiety and other mood states, control of appetite, analgesia, motor activity (catalepsy with very high doses), inflammatory and immune responses and blood pressure.
THC also binds to CB receptors and has been shown to release dopamine from the pre-frontal cortex (reward pathway), as does heroin, nicotine and amphetamine, which might account for some of its reinforcing properties.
Cannabinoids are lipid soluble and accumulate in fatty tissues and reach peak concentrations in 4-5 days. They are metabolised by the liver. Elimination half-life of THC is about 7 days, and complete elimination of a single dose may take up to 30 days during which time metabolites can be detected in urine [4].
Withdrawal
Prior to the 1990’s clinicians were sceptical about the prevalence and clinical significance of cannabis withdrawal. With the discovery of the endogenous cannabinoid system and the production of a cannabinoid antagonist, animal models have demonstrated unequivocally a discrete cannabis withdrawal syndrome.
Withdrawal is typically associated with cessation of heavy or daily cannabis use, however the extent to which withdrawal symptoms occur in light or non-daily users is as yet unclear. The following symptoms are typical of cannabis withdrawal [5]:
Most common symptoms are:
- Anger, aggression, irritability
- Anxiety/nervousness
- Decreased appetite or weight loss
- Restlessness
- Sleep difficulties including strange dreams
- Less common symptoms
- Chills
- Depressed mood
- Stomach pain/physical discomfort
- Shakiness
- Sweating.
Most symptoms tend to emerge on day 1-2 of abstinence, peak between days 2 and 6, and most symptoms abate within 2-3 weeks [5, 6].
Tobacco and cannabis use
The concomitant use of tobacco with cannabis is prevalent in Australia. Some evidence suggests withdrawal from nicotine and cannabis at the same time leads to more severe withdrawal symptoms than withdrawal from either substance alone [7].
Similarly, tobacco users are more likely to report stronger cannabis withdrawal symptoms than non-tobacco users [8]. In this case the role of nicotine replacement therapy (NRT) should be considered.
Treatment options
Treatment of cannabis-use problems is primarily psychosocial. Cognitive behaviour therapy (CBT) and motivational enhancement is demonstrated as effective in reducing cannabis use among heavy and dependent users [2, 9].
Limited literature exists regarding the role of medications in the treatment of cannabis-use disorder [2, 10].
References
1. AIHW, 2007 National Drug Strategy Household Survey. 2007, Australian Institute of Health and Welfare.
2. Copeland, J., Gerber, S., and Swift, W., Evidence-based answers to cannabis questions: a review of the literature. 2006: Australian National Council on Drugs.
3. Australian Institute of Health and Welfare, Interactive alcohol and other drug treatment services data cubes: 2007-2008. 2007/08, AIHW.
4. Ashton, C.H., Pharmacology and effects of cannabis: a brief review. The British Journal of Psychiatry, 2001. 101 - 106(178).
5. Budney, A.J. and Hughes, J.R., The cannabis withdrawal syndrome. Current Opinion in Psychiatry, 2006. 19(3): p. 233-238.
6. Kouri, E.M. and Pope, H.J.J., Abstinence Symptoms During Withdrawal From Chronic Marijuana Use. Experimental and clinical psychopharmacology, 2000. 8(4): p. 483-92.
7. Vandrey, R.G., Budney, A.J., Hughes, J.R., and Liguori, A., A within subject comparison of withdrawal symptoms during abstinence from cannabis, tobacco, and both substances. Drug and Alcohol Dependence, 2008. 92(1-3): p. 48-54.
8. Agrawal, A., Pergadia, M.L., and Lynskey, M.T., Is There Evidence for Symptoms of Cannabis Withdrawal in the National Epidemiologic Survey of Alcohol and Related Conditions? The American Journal on Addictions, 2008. 17: p. 199-208.
9. Copeland, J., Swift, W., Roffman, R., and Stephens, R., A randomised controlled trial of brief cognitive-behavioral interventions for cannabis use disorder. Journal of Substance Abuse Treatment, 2001. 21(2): p. 55-64.
10. Hart, C.L., Increasing treatment options for cannabis dependence: A review of potential pharmacotherapies. Drug and Alcohol Dependence, 2005. 80(2): p. 147-159.