Motivation and emotion/Book/2016/Cannabis and anxiety

Cannabis and anxiety:
What are the effects of cannabis and cannabis withdrawal on anxiety?

Multimedia presentation (3 min)

Overview

Figure 1. A leaf from a Cannabis sativa plant.

Anxiety is an emotion many individuals experience, whether it be on a daily basis or an infrequent occurrence in their lives. Characterised by heightened arousal and alertness provoked by perceived threats to the individual, it is an emotion that, if prolonged and severe, can lead to psychological disorders such as social anxiety disorder (APA, 2013). While there are many treatments to relieve anxiety for the short- and long-term, some individuals may take up illicit drugs as a form of coping. One such drug is cannabis, a commonly used psychoactive substance in Western society (Kedzior & Laeber, 2014). While the empirical literature does suggest cannabis can provide short-term relief for anxiety, long-term effects are more severe, possibly leading to the development of anxiety disorders (Hayatbakhsh et al., 2007), as well as severe drug-dependence and withdrawal symptoms (Budney et al., 2004). This has implications on severity of anxiety the individual experiences both on and off the drug.

To investigate the effects that cannabis has on both relieving and increasing anxiety, this chapter will outline:

1. What cannabis is and how it affects an individual's body, mind, and emotions.
2. Define anxiety and some of the theories used to explain its development and role in daily functioning.
3. Explore the relationship between cannabis and anxiety, specifically the empirical effects the former has on the latter.
4. How cannabis withdrawal effects anxiety.

Cannabis

Figure 2. A lit marijuana 'joint'.

Cannabis, more commonly known as ‘marijuana’, is a psychoactive drug derived from the leaves of the Cannabis plant (Guy, Whittle, & Robson, 2004). The plant's leaves are composed of 483 substances, including Tetrahydrocannabinol (THC), the principle cannabinoid that gives the drug its psychoactive properties (Russo, 2013). It’s commonly consumed through smoking ‘joints’, hand-made rolled up cigarettes containing ground up cannabis leaves, or a bong (Hall, 2014). However, it can also be used in and consumed through food, drinks, oils, and vaporization (Russo, 2013; Crippa et al., 2009).

In terms of prevalence, cannabis is one of the most widely used psychoactive drugs in Western society (UNODC, 2011; Kedzior & Laeber, 2014). Within Australia, it is estimated that 34.8% of the population aged 14 years and over have used cannabis in the past at least once (Alcohol and Drug Foundation, 2016). Furthermore, it is the most commonly used illicit drug amongst Australians aged 14 to 24 years old (Alcohol and Drug Foundation, 2016). Historically, the most frequently used strain of cannabis is the Cannabis satvia plant, notably for medicinal and religious purposes (Guy et al., 2004). In modern society, the drug is utilized for various purposes - particularly recreational - and is illegal to consume or be in possession of it in many countries (UNODC, 2011). Because of this and its known effects on the body, the drug has negative connotations associated with it, and users often experience ostracism from society, leading to a high risk of developing depression and other deficits to their quality of life (Barnwell, Earleywine, & Wilcox, 2006). Despite this, some argue in favor of legalizing cannabis-use for medicinal purposes, as it can give pain-relief to patients with acute or chronic pain and reduces the symptoms of epilepsy (Guy et al., 2004).

The effects of cannabis

Depending on the dosage, how it is consumed, the plant strain used, and certain physical factors (such as weight and general health), cannabis can have a wide range of physiological and psychological effects on an individual (Kedzior & Laeber, 2014; Guy et al, 2004). The severity, longevity, and immediacy of these effects is also dependent on how the drug is consumed. For example, cannabis consumed orally through food or drink tends to take longer to have an effect; however, the effects last longer than when consumed through inhalation (Guy et al, 2004). Typically when smoking cannabis, the effects manifest several minutes after consumption and can last for one to three hours (Guy et al., 2004).

Figure 3. Some of the physiological effects of cannabis.

On a physiological level, cannabis mainly affects the endocannabinoid system, a complex network composed of cannabinoid receptors located throughout the body (Aizpurua-Olaizola et al., 2016). These receptors are responsible for appetite, memory, mood, and pain management (Aizpurua-Olaizola et al., 2016). When cannabis is introduced into the body, it affects these physiological processes by binding the system's receptors, causing various responses and effects to occur (Aizpurua-Olaizola et al., 2016). Some of these short-term effects include feelings of relaxation and euphoria, reddening of the eyes, dry mouth, limited short-term memory, increased heart rate, and increased appetite (Hall, 2014; Jones, 2002) (see Table 1).

Most notable is cannabis' effects on the nucleus accumbens (NAc), a brain structure known for its significant role in reinforcement learning and generating pleasure as a reward (Hoffman, Caulder, & Lupica, 2003). When THC binds the cannabinoid receptors located in the axons surrounding the NAc, the release of GABA is inhibited, thus causing the NAc to become hyperactive and produce euphoric feelings via releases of dopamine (Hoffman, Caulder, & Lupica, 2003). The user goes on to associate this increase in positive emotion with cannabis-use, thereby increasing the chances of developing an addiction to the drug (Hayatbakhsh et al., 2007).

Cannabis withdrawal

After prolonged and regular use, a user will likely develop a dependence for cannabis and go on to gain a tolerance towards it, thus decreasing the impact of the drug's effects (Budney et al., 2004). As a result, they increase their dosage to achieve the same level effects previously had (Budney et al., 2004). At this point, should a user reduce the amount they normally consume or decide to completely cease use, withdrawal occurs (Budney et al., 2004). Onset for withdrawal symptoms is one to two days after discontinued or decreased cannabis-use and can last up to at least 14 days (Budney et al., 2003). These symptoms include cravings, decreased appetite, trembling, irregular or poor sleep cycles, and increased agitation and aggression (Budney et al., 2004; Budney et al., 2003) (see Table 1).

Table 1.

A summary of cannabis' effects on a user over three time periods (Crippa et al., 2009; Hall, 2014; Guy et al., 2004; Budney et al., 2004).

Time period	Somatic	Mental	Emotional
Short-term (while on "high")	Muscle relaxation. Reddening of the eyes. Dry mouth. Increased heart rate. Increased appetite. Increased awareness of hot and cold. Slower reflexes.	Decreased short-term memory. Psychosis.	Relaxed. Sleepy. Euphoric. Mild anxiety (if dosage is large).
Long-term	Inhibited sex drive and fertility. Sore throat.	Developing an addiction. Memory loss. Deficits in working-memory. Learning difficulties.	Mood swings.
Withdrawal	Trembling and chills. Sweating. Irregular sleep and circadian rhythms. Decreased appetite.	Cravings.	Anxiety and irritability. Aggression.

Quiz

1 Which cannabinoid is credited as the primary substance for giving cannabis its psychoactive properties?

	Cannabidiol
	Tetrahydrocannabinol
	Tetrahydrocannabivarin
	Cannabinol

2 Which of the following is NOT a long-term effect of cannabis?

	Sore throat
	Memory loss
	Inhibited sex drive
	Reddening of the eyes

3 On average, how many Australians over the age of 14 have tried cannabis at least once?

	43.5%
	34.8%
	38.4%
	40%

4 What can happen once an individual develops a tolerance for cannabis?

	The user will consume more cannabis to increase the effects further.
	The user will increase their dosage to achieve the same level of effect the drug had before.
	The user will consume less cannabis because the psychoactive effects have increased.
	The user will quit using cannabis.

Anxiety

Anxiety is an aversive emotional state characterised by heightened arousal and alertness in response to perceived threats to the individual (Eysenck et al., 2007). Although similar to fear, the essential differences are the longevity of the emotion - as fear is more short-term compared to anxiety - and what is perceived to be a threat - fear is brought about by an immediate perceived threat and acts as a coping or survival mechanism, whereas anxiety is produced when thinking about future expected events perceived to be threatening to some degree (Ohman, 2008). Symptoms of anxiety can include increased heart rate, muscle tension, feelings of restlessness or worry, shortness of breath, and sweating (APA, 2013). However, if anxiety becomes severe and prolonged, it can develop into a mental disorder and present more symptoms that further impair on the individual's well-being and quality of life (APA 2013).

There have been many theories developed to investigate and understand the development, activation, and psychological mechanisms of anxiety. Chief among them are attentional control theory and processing efficacy theory.

Attentional control theory

Developed by Eysenck and colleagues (2007), the attentional control theory primarily focuses on how state anxiety (the present level of anxiety felt by a person) affects the cognitive processing of individuals in the general population rather then people with anxiety disorders (Eysenck et al., 2007). Furthermore, it examines how impairments to executive functions, specifically attentional control, and cognitive performance can generate anxiety within an individual (Eysenck et al., 2007).

The theory proposes that anxiety can be produced if an individual perceives that a threat will endanger their current goal (Eysenck et al., 2007). It further suggests that certain variables, such as perceived situational stress and trait anxiety, can act as stressors that sustain or increase state anxiety (Eysenck et al., 2007). The individual will then attempt to develop a coping strategy using their cognitive processes that involve either confronting or avoiding the goal-threatening stimuli or situation (Eysenck et al., 2007). If unsuccessful in creating a solution, the individual can become worried about or fixated on the stressors, thus increasing anxiety levels further (Eysenck et al., 2007).

Processing efficacy theory

Similar to attentional control theory, processing efficacy theory looks at how impairments to cognitive components that can cause anxiety in an individual (Murray & Janelle, 2007). However, where it differs from attentional control theory is in its concentration on performance anxiety and exploration of how anxiety's effects are perpetual and can weaken an individual (Murray & Janelle, 2007). Essentially, worry is the key component to producing and facilitating anxiety, as it reduces the number of resources available to perform tasks proficiently (Hardy & Hutchinson, 2007).

The level of performance for a task is established by the level of state anxiety an individual experiences (Murray & Janelle, 2007). This in turn is determined by trait anxiety and situational stress (Murray & Janelle, 2007). When instigated, cognitive anxiety (worry) takes over some of the resources used in working memory (Murray & Janelle, 2007), a component of short-term memory concerned with language and perception information processing (Kanayama et al., 2004). As a result, reserved cognitive resources are put towards maintaining task performance. Finally, the theory suggests anxiety acts as a motivational force, due worry placing emphasis on how important the task is to the individual (Hardy & Hutchinson, 2007).

In the end, performance effectiveness (the ability and quality of task performance) is sustained, while performance efficacy (the number of resources spent and how well these improved task performance) is diminished based on how many resources are put towards task performance (Hardy & Hutchinson, 2007; Murray & Janelle, 2007).

Quiz

1 Symptoms of anxiety include shortness of breath, feelings of worry and restlessness, _____, _____, and _____.

	Decreased heart rate, itchy skin, impaired short-term memory.
	Increased heart rate, sweating, trembling.
	Sweating, increased heart rate, muscle tension.
	Trembling, decreased appetite, sweating.

2 True or false: Eysneck and colleagues's (2007) attentional control theory proposes anxiety is the result of impaired cognitived processes and attentional control, trait anxiety, and situation stressors.

	True
	False

3 True or false: Processing efficacy theory proposes the level of task performance is determined by the level of state anxiety.

	True
	False

Effects of cannabis on anxiety

Reliever

Figure 4. Cannabidiol (CBD) molecule.

Considering the nature of anxiety, it is not surprising that cannabis, a drug that can generate euphoric and relaxed feelings, could be used as a coping strategy. Research has found anxiety relief to be one of the chief reasons to consume cannabis (Kedzior & Laeber, 2014). Participants in many of these studies see cannabis-use as a form of 'self-medication' (Crippa et al., 2009; Kedzior & Laeber, 2014). This has brought about substantial research to investigate the ultimate effectiveness of using cannabis and cannabinoids to relieve anxiety, particularly for anxiety disorders (Degenhardt & Lynskey, 2001). For example, Bergamaschi and colleagues (2011) administered pills containing 600mg of the cannabinoid Cannabidiol (CBD) to participants with social anxiety and had them perform a four minute speech. Their results indicated CBD significantly reduced anxiety and discomfort about public speaking (Bergamaschi et al., 2011).

On the other hand, some research has shown first-time cannabis users or high dosages of the drug can cause brief anxiety reactions as a short-term effect (Kedzior & Laeber, 2014; Degenhardt & Lynskey, 2001; Crippa et al., 2009). Long-term users often report cannabis relieves anxiety (Gruber, Pope, & , 1997; Schofield et al., 2006). However, a limitation with some of these studies is their small samples sizes or recruitment of participants from specific population, such as those with mental disorders (Degenhardt & Lynskey, 2001).

Contributor

Several studies have shown cannabis-use and dependence are correlated with greater levels of anxiety (Crippa et al., 2009), with some proposing those with depression or an anxiety disorder are more likely to use the drug (Kedzior & Laeber, 2014). Additionally, cannabis could worsen anxiety that is preexistent to use depending on a range of factors including, gender (Schofield et al., 2006) and genetic vulnerabilities (Kedzior & Laeber, 2014). Lastly, the increased of cannabis-use could be predicted through the level of state anxiety (Clough et al., 2005; Crippa et al., 2009). All of this would suggest a cyclical and complex relationship between anxiety and cannabis, with anxiety as both a catalyst for and being the result of cannabis-use.

Further research has looked into cannabis' relationship with anxiety disorders. In some cases, cannabis use could be predicted by the development of anxiety disorders in adolescence or a genetic factors such as vulnerability in the endocannabinoid system (Crippa et al., 2009). In others, cannabis-use predicted the development of anxiety disorders, as seen in Hayatbakhsh and colleagues' (2007) longitudinal study. The researchers followed a sample of 3,239 Australians from birth to the age of 21; their results indicated those who started using cannabis before they were 15 years old and continued to use it heavily at the age of 21 were more likely to suffer from severe anxiety and develop an anxiety disorder symptoms in young adulthood (Hayatbakhsh et al., 2007). Conversely, other research has suggested no connection between cannabis-use and the development of anxiety disorders once confounding variables were account for (Crippa et al., 2009).

Effects of cannabis-withdrawal on anxiety

Figure 5. A tetrahydrocannabinol (THC) molecule, the cannabhinoid that gives cannabis its psychoactive properties.

One of the main symptoms of cannabis-withdrawal is an increase in anxiety (Budney et al., 2003). As such, there is a wealth of literature dedicated to investigating the relationship between anxiety and cannabis withdrawal (Budney et al., 2004). Much of the research shares similarities to cannabis-use studies, as they examine the use of cannabinoids as a reliever for withdrawal symptoms (Budney et al., 2004). The majority of cannabis withdrawal studies use inpatient samples. For instance, a study conducted by Haney and colleagues (1999) had heavy cannabis smokers take placebo pills containing THC four times a day on four separate 3-day long periods for the duration fo the experiment. During the time periods when they were administered a placebo, participants showed significant increases in anxiety, suggesting an association with the abstinence from THC (Haney et al., 1999). Similarly, a study by Budney and colleagues (2007) found administering 30 to 90 mg of THC helped to relieve withdrawal symptoms in three 5-day long abstinence periods. They concluded that using THC alone could help to gradually withdraw from cannabis-use (Budney et al., 2007).

In addition to inpatient research, outpatient research has been used and has produced insightful results about how environmental cue could trigger withdrawal symptoms and increase anxiety (Budney et al., 2004). These investigations have also looked into using other substances and pharmaceuticals have been tested to see if they could decrease the anxiety induced by cannabis withdrawal. Notable among these is Haney and colleagues (2003) study, which utilised both an outpatient and inpatient condition; essentially, they set out to test the effectiveness of the anti-depressant nefazodone for reducing anxiety caused by cannabis-withdrawal. During placebo conditions, participants exhibited high levels of anxiety, but after taking nefazodone, it decreased significantly along with muscle pain (Haney et al., 2003). However, the anti-depressant could not reduce other withdrawal symptoms such as increased irritation and irregular or interrupted sleeping (Haney et al., 2003).

Application of the theories

Attentional control theory

There are a number of ways to apply attentional control theory to cannabis-use. First, the theory proposes that anxiety is created by a combination of deficits in cognitive performance and attentional control when in the presence of a goal-threatening situation or stimuli (Eysenck et al., 2007). In relation to this, early and recent empirical literature suggests long-term and chronic cannabis users suffer from poor attentional control (Abdullaev et al., 2010; Ehrenreich et al., 1999). This implies that long-term cannabis use leads to a decline in attentional control, thus generating and facilitating anxiety in a user (Eysenck et al., 2007).

A second application for the theory is for cannabis withdrawal. Aside from impaired cognitive resources, attention control theory also suggests other factors can act as stressors that exacerbate anxiety (Eysenck et al., 2007). Hypothetically, the symptoms of withdrawal from cannabis may act as stressor on the cognition of an ex-user and increase their level of anxiety (Eysenck et al., 2007). Additionally, cognitive symptoms such as cravings may impair attentional control and other cognitive resources used to obtain goals, suggesting to be the cause of anxiety (Eysenck et al., 2007).

Processing efficacy theory

A core component of the processing efficacy theory is the diminished capabilities of the working memory when cognitive anxiety takes control over it (Murray & Janelle, 2007). Given that long-term cannabis-use can result in deficits in working memory (Kanayama et al., 2004), this could potentially cause anxiety to increase. Specifically, the impairments of cannabis-use limit the resources of working memory, thus the few resources left are consumed by cognitive anxiety. Because of this increase in anxiety, with what little resources are available, task performance can be negatively impacted upon and performance efficacy could become severely low (Murray & Janelle, 2007; Hardy & Hutchinson, 2007). However, higher levels of cognitive anxiety could also create higher efforts and motivations to improve and sustain performance effectiveness (Murray & Janelle, 2007).

Quiz

1 True or false: There is a chance a first time cannabis users could experience mild anxiety just after consuming the drug.

	True
	False

2 True or false: Hayatbakhsh et al. (2007) found that those who started using cannabis past the age of 21 were more likely to develop an anxiety disorder.

	True
	False

3 Which two cannabinoids have been used in experimental studies to relieve anxiety?

	Cannabidiol & Tetrahydrocannabivarin
	Tetrahydrocannabinol & Cannabidivarin
	Cannabichromene & Cannabidiol
	Tetrahydrocannabinol & Cannabidiol

4 Which withdrawal symptoms was the antidepressant nefazodone able to reduce the effect of?

	All of them.
	Irregular sleeping patterns, irritability, and anxiety.
	Anxiety and muscle pain.
	Just anxiety.

Conclusion

Cannabis has a complex relationship with anxiety, acting as both a cause and effect of the adverse emotion, as well as a being a short-term reliever and a perpetuator of or contributor towards it in the long-term (Crippa et al., 2009; Hayatbakhsh et al., 2007; Kedzior & Laeber, 2014). Regardless of the short-term relief cannabis can provide, the drug can have negative long-term consequences for not only the development of pre-existing or newly acquired anxiety, but also other bodily functions (Crippa et al, 2009; Hall, 2014; Kedzior & Laeber, 2014). Furthermore, should a user become dependant it can lead to severe withdrawal symptoms (including high levels of anxiety) and the development of anxiety disorders (Crippa et al., 2009; Kedzior & Laeber, 2014; Budney et al., 2004). Finally, using attentional control theory and processing efficacy theory, it becomes clear cannabis can have negative effects on anxiety in cognition and cognitive processes as well (Eysenck et al., 2007; Murray & Janelle, 2007; Kedzior & Laeber, 2014). There are other treatments and methods of coping for anxiety which would lead to physiologically, psychologically and emotionally healthier outcomes then using cannabis (Crippa et al., 2009).

See also

Cannabis and emotion (2013 book chapter)

Cannabis and negative emotion (2016 book chapter)

References

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Alcohol and Drug Foundation (2016). Statistics - Drug Prevalence. Retrieved from Alcohol and Drug Foundation website: http://www.druginfo.adf.org.au/topics/quick-statistics#cannabis

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Bergamaschi, M. M., Queiroz, R. H. C., Chagas, M. H. N., de Oliveira, D. C. G., De Martinis, B. S., Kapczinski, F., Quevedo, J., Roesler, .R, Schröder, N., Nardi, A. E., Martín-Santos, R., Hallak, J. E. C., Zuard, A. W., & Martín-Santos, R. (2011). Cannabidiol reduces the anxiety induced by simulated public speaking in treatment-naive social phobia patients. Neuropsychopharmacology, 36(6), 1219-1226.

Budney, A. J., Hughes, J. R., Moore, B. A., & Vandrey, R. (2004). Review of the validity and significance of cannabis withdrawal syndrome. American journal of Psychiatry, 161(11), 1967-1977.

Budney, A. J., Moore, B. A., Vandrey, R. G., & Hughes, J. R. (2003). The time course and significance of cannabis withdrawal. Journal of abnormal psychology, 112(3), 393-402.

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Clough, A. R., D'abbs, P., Cairney, S., Gray, D., Maruff, P., Parker, R., & O'reilly, B. (2005). Adverse mental health effects of cannabis use in two indigenous communities in Arnhem Land, Northern Territory, Australia: exploratory study. Australian and New Zealand Journal of Psychiatry, 39(7), 612-620.

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Degenhardt, L., Hall, W., & Lynskey, M. (2001). The relationship between cannabis use, depression and anxiety among Australian adults: findings from the National Survey of Mental Health and Well-Being. Social psychiatry and psychiatric epidemiology, 36(5), 219-227.

Ehrenreich, H., Rinn, T., Kunert, H. J., Moeller, M. R., Poser, W., Schilling, L., Gigernzer, G., & Hoehe, M. R. (1999). Specific attentional dysfunction in adults following early start of cannabis use. Psychopharmacology, 142(3), 295-301.

Eysenck, M. W., Derakshan, N., Santos, R., & Calvo, M. G. (2007). Anxiety and cognitive performance: attentional control theory. Emotion, 7(2), 336-353. DOI: 10.1037/1528-3542.7.2.336

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Guy, G. W., Whittle, B. A., & Robson, P. J. (2004). The Medicinal Uses of Cannabis and Cannabinoids. Cornwall, Great Britian: Pharmaceutical Press.

Hall, W. (2014). What has research over the past two decades revealed about the adverse health effects of recreational cannabis use?. Addiction, 110(1), 19-35.

Haney, M., Hart, C. L., Ward, A. S., & Foltin, R. W. (2003). Nefazodone decreases anxiety during marijuana withdrawal in humans. Psychopharmacology, 165(2), 157-165. DOI: 10.1007/s00213-002-1210-3 ·

Haney, M., Ward, A. S., Comer, S. D., Foltin, R. W., & Fischman, M. W. (1999). Abstinence symptoms following oral THC administration to humans. Psychopharmacology, 141(4), 385-394.

Hardy, L., & Hutchinson, A. (2007). Effects of performance anxiety on effort and performance in rock climbing: A test of processing efficiency theory. Anxiety, stress, and coping, 20(2), 147-161.

Hayatbakhsh, M. R., Najman, J. M., Jamrozik, K., Mamun, A. A., Alati, R., & Bor, W. (2007). Cannabis and anxiety and depression in young adults: a large prospective study. Journal of the American Academy of Child & Adolescent Psychiatry, 46(3), 408-417. DOI: 10.1097/CHI.0b013e31802dc54d

Hoffman, A. F., Oz, M., Caulder, T., & Lupica, C. R. (2003). Functional tolerance and blockade of long-term depression at synapses in the nucleus accumbens after chronic cannabinoid exposure. The Journal of neuroscience, 23(12), 4815-4820.

Kanayama, G., Rogowska, J., Pope, H. G., Gruber, S. A., & Yurgelun-Todd, D. A. (2004). Spatial working memory in heavy cannabis users: a functional magnetic resonance imaging study. Psychopharmacology, 176(3-4), 239-247.

Kedzior, K. K., & Laeber, L. T. (2014). A positive association between anxiety disorders and cannabis use or cannabis use disorders in the general population-a meta-analysis of 31 studies. BMC psychiatry, 14(1), 1.

Jones, R. T. (2002). Cardiovascular system effects of marijuana. The Journal of Clinical Pharmacology, 42(1), 58-63. doi:10.1002/j.1552-4604.2002.tb06004.x

Murray, N. P., & Janelle, C. M. (2007). Event-related potential evidence for the processing efficiency theory. Journal of Sports Sciences, 25(2), 161-171.

Ohman, A. (2008) Fear and anxiety. In M. Lewis, J. M. Haviland-Jones, & L. F. Barrett (Eds.), Handbook of emotions (3rd ef., pp. 709-729). New York: Guilford Press.

Russo, E. B. (2013). Cannabis and Cannabinoids: Pharmacology, Toxicology, and Therapeutic Potential. Binghamton, NY: The Haworth Integrative Healing Press.

Schofield, D., Tennant, C., Nash, L., Degenhardt, L., Cornish, A., Hobbs, C., & Brennan, G. (2006). Reasons for cannabis use in psychosis. Australian and New Zealand Journal of Psychiatry, 40(6-7), 570-574.

United Nations Office on Drugs and Crime (UNODC) (2011). World Drug Report 2011. Vienna, Austria: United Nations Publication.

External links

• Factsheet from Drugs and Alcohol Foundation
• UNODC's 2011 World Drug Report