Misplaced Pages

Revision as of 06:25, 16 December 2013

This article has multiple issues. Please help improve it or discuss these issues on the talk page. (Learn how and when to remove these messages) This article needs more reliable medical references for verification or relies too heavily on primary sources. Please review the contents of the article and add the appropriate references if you can. Unsourced or poorly sourced material may be challenged and removed. Find sources: "Long-term effects of cannabis" – news · newspapers · books · scholar · JSTOR (November 2013) The neutrality of this article is disputed. Relevant discussion may be found on the talk page. Please do not remove this message until conditions to do so are met. (November 2013) (Learn how and when to remove this message) This article possibly contains original research. Please improve it by verifying the claims made and adding inline citations. Statements consisting only of original research should be removed. (November 2013) (Learn how and when to remove this message) (Learn how and when to remove this message)

The long term effects of cannabis have been the subject of ongoing debate. Because cannabis is illegal in most countries, research presents a challenge; as such there remains much to be concluded. Studies have investigated both the detrimental and beneficial effects of long-term use of cannabis. The vast majority of this research focuses on those who use cannabis at least once a day. Recent research has investigated whether its long-term effects on adolescents differ from those on adults.

A 2013 literature review said that exposure to marijuana had biologically-based physical, mental, behavioral and social health consequences and was "associated with diseases of the liver (particularly with co-existing hepatitis C), lungs, heart, and vasculature". The authors cautioned that "evidence is needed, and further research should be considered, to prove causal associations of marijuana with many physical health conditions".

Data supporting negative effects of cannabis alone are weak.

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Long-term effects of cannabis" – news · newspapers · books · scholar · JSTOR (December 2013) (Learn how and when to remove this message)

Discerning between correlation and causation is an important consideration. Studies exist showing both negative and positive effects, and much is conflicting.

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Long-term effects of cannabis" – news · newspapers · books · scholar · JSTOR (December 2013) (Learn how and when to remove this message)

For instance, studies have associated heavy cannabis use with the development of various mental disorders, while other science points to both an ameliorative effect

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Long-term effects of cannabis" – news · newspapers · books · scholar · JSTOR (December 2013) (Learn how and when to remove this message)

and no relationship whatsoever.

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Long-term effects of cannabis" – news · newspapers · books · scholar · JSTOR (December 2013) (Learn how and when to remove this message)

Memory and intelligence

Long term exposure to cannabis poses a risk of irreversible cognitive impairment in children and adolescents; other than for the very highest of doses, no similar risk has been established for adults. Changes in attention, psychomotor task ability, and short-term memory are associated with very recent (12 to 24 hours) marijuana use. Any long-term central nervous system effects of the residual drug are indistinguishable from variations in the user's susceptibility, or any pre-existing psychiatric disorder.

Dependency

Cannabis is the most widely used illicit drug in the Western world, and in the US 10 to 20% of consumers who use cannabis daily become dependent. Cannabis use disorder is defined in the fifth revision of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) as a condition requiring treatment. Although no medication is known to be effective in combating dependency, combinations of psychotherapy such as cognitive behavioural therapy and motivational enhancement therapy have achieved some success.

Mental health

Cannabis use is not free of risk. Although cannabis is not believed to cause psychosis alone, it may be a contributory factor, particularly when combined with an existing susceptibility. Higher levels and frequencies of use, and exposure from an early age carry the highest risk of developing or exacerbating psychiatric disorders. It is likely that the two principal active ingredients of cannabis, delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD) have opposing effects, with CBD counteracting the adverse psychological effects of THC.

Acute psychosis

Although there has been an association noted between cases of acute psychosis and long-term cannabis use, the precise nature of the relationship is controversial; evidence suggests that cannabis use may worsen psychotic symptoms and increase the risk of relapse.

Chronic psychosis

There is no support for the hypothesis that cannabis causes cases of psychosis which would not have occurred otherwise. A risk does exist in some individuals with a predisposition to mental illness to develop symptoms of psychosis; the predisposing factors identified include genetic liability, childhood trauma and urban upbringing. Although most do not experience such problems, some cannabis users develop chronic psychosis with a risk directly related to high dosage, frequency of use and early age of introduction to the drug.

Schizophrenia

Among people with schizophrenia there is insufficient evidence to determine whether cannabis use leads to improvement or deterioration of the condition.

Use of cannabis in adolescence or earlier increases the risk of developing schizoaffective disorders in adult life, although the proportion of these cases is small. Susceptibility is most often found in users with at least one copy of the polymorphic COMT gene.

Cannabis with a high THC to CBD ratio produces a higher incidence of psychological effects, and CBD shows antipsychotic and neuroprotective properties, acting as an antagonist to some of the effects of THC.

Depressive disorder

Less attention has been given to the association between cannabis use and depression, though according to the Australian National Drug & Alcohol Research Centre, it is possible this is because cannabis users who have depression are less likely to access treatment than those with psychosis. Chen and colleagues (2002) re-analyzed the US National Comorbidity Survey (NCS) to examine the relationship between cannabis use and a major depressive episode and discovered that the risk of first major depressive episode (MDE) was moderately associated with the number of occasions of cannabis use and with more advanced stages of cannabis use. Relative to newer users, non-dependent cannabis users had 1.6 times greater risk of MDE. Cannabis dependence was associated with a 3.4 times greater risk of major depression.

A 2005 literature review of the use of cannabis in mental health patients found that the drug can have very different effects on different patients with bipolar disorder. Although "no controlled trials of THC have been done in bipolar disorder", there is anecdotal evidence that "for some people marijuana is beneficial" as a treatment for bipolar disorder. The reviewers suggested that randomized studies and standardized administration techniques would be required to create conclusive evidence.

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Long-term effects of cannabis" – news · newspapers · books · scholar · JSTOR (November 2013) (Learn how and when to remove this message)

Suicidality

A 2010 systematic review assessing the risk of cannabis-related mortality found four studies on suicide that met inclusion criteria on the literature review, and said that three studies found an increased risk of suicide associated with cannabis use and an increased risk of completed suicide. One study found early use of cannabis associated with a higher risk of attempted suicide. The authors concluded that evidence was "unclear as to whether regular cannabis use increases the risk of suicide"; limitations of the review were a) variables such as co-occurring depression or alcohol use were not controlled for in the studies on suicide; b) many studies on cannabis do not have long enough follow-up periods on regular users; c) studies "used diverse exposure and outcome measures that make comparison across studies problematic".

Cognitive decline

Cannabinoids are strong antioxidants and therefore defends cells from β-amyloid, the peptide that causes Alzheimer's disease.

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Long-term effects of cannabis" – news · newspapers · books · scholar · JSTOR (December 2013) (Learn how and when to remove this message)

Some studies have found that cannabis has no effect on ageing-related cognitive decline

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Long-term effects of cannabis" – news · newspapers · books · scholar · JSTOR (December 2013) (Learn how and when to remove this message)

while others suggest that it slows cognitive decline through its antioxidant effect. The cannabinoids present in cannabis lessen cell damage and death from ischemia, likely due to their antioxidant properties.

Behavioral effects

Government studies often point to statistical data accumulated by methods like the National Household Survey on Drug Abuse (NHSDA), the Monitoring the Future (MTF) study, and the Arrestee Drug Abuse Monitoring (ADAM) program, which claim lower school averages and higher dropout rates among users than non-users. However, these surveys are usually self-administered and may be anonymous, which greatly reduces their reliability. Additionally, while they establish a relationship between cannabis use and academic underperformance they do not determine whether the former causes the latter. The ADAM study is conducted anonymously, but only seeks information from a sample of people who have been arrested for drug-related offenses. Socially deviant behavior may be found more frequently in individuals of the criminal justice system compared to those in the general population, including non-users. In response, independent studies of college students have shown that there was no difference in grade point average, and achievement, between cannabis users and non-users. However, the users surveyed had slightly more difficulty deciding on career goals, and a smaller number were seeking advanced professional degrees.

A longitudinal study of heavy cannabis users from ages 14 to 25 in a Christchurch, New Zealand birth cohort concluded, "The results of the present study suggest that increasing cannabis use in late adolescence and early adulthood is associated with a range of adverse outcomes in later life. High levels of cannabis use are related to poorer educational outcomes, lower income, greater welfare dependence and unemployment and lower relationship and life satisfaction. The findings add to a growing body of knowledge regarding the adverse consequences of heavy cannabis use." However, this study primarily established correlation rather than causality.

A study published in the American Journal of Epidemiology in 2011, concluded that the prevalence of obesity is lower in cannabis users than in nonusers. A 2013 study confirmed this correlation and also found that cannabis users had better insulin resistance, lower insulin levels, and higher high-density lipoprotein ("good cholesterol") levels.

A 2008 study published in the British Journal of Psychiatry showed significant differences in Oxford-Liverpool Inventory of Feelings and Experiences scores between three groups: The first consisted of non-cannabis users, the second of users who tested positive for THC only, and the third consisted of users who tested positive for both THC and CBD. The Δ9-THC only subset scored significantly higher for unusual experiences, while users of both THC and CBD had much lower introvertive anhedonia scores. This suggests that CBD prevents some of the negative behavioral effects of THC.

Gateway drug hypothesis

The gateway drug hypothesis asserts that the use of cannabis may ultimately lead to the use of harder drugs.

Cancer

According to a 2013 literature review, marijuana could be carcinogenic, but there are methodological limitations in studies making it difficult to establish a link between marijuana use and cancer risk. The authors say that bladder cancer does seem to be linked to habitual marijuana use, and that there may be a risk for cancers of the head and neck among long-term (more than 20 years) users. Gordon and colleagues said, "there does appear to be an increased risk of cancer (particularly head and neck, lung, and bladder cancer) for those who use marijuana over a period of time, although what length of time that this risk increases is uncertain."

Glioma

A 2003 review of potential cannabinoid use to treat glioma said the "possible antitumor effects in patients have not been well established".

Testicular

In 2012 WebMD said that a number of studies had suggested a link between cannabis use and an increased risk of testicular cancer, but that the overall risk remained small and that more research is needed to confirm the findings. According to Gordon and colleagues, "several recent studies suggest an association between marijuana use and testicular germ cell tumors".

Lung

Gordon and colleagues in a 2013 literature review said: "Unfortunately, methodological limitations in many of the reviewed studies, including selection bias, small sample size, limited generalizability, and lack of adjustment for tobacco smoking, may limit the ability to attribute cancer risk solely to marijuana use." Reviewing studies adjusted for age and tobacco use, they said there was a risk of lung cancer even after adjusting for tobacco use, but that the period of time over which the risk increases is uncertain.

Cannabis smoke contains thousands of organic and inorganic chemicals, including many of the same carcinogens as tobacco smoke. A 2012 literature review by the British Lung Foundation suggested that the risk of developing lung cancer is nearly 20 times higher from smoking typical cannabis cigarettes than from smoking tobacco cigarettes, due to deeper, longer inhalation and the lack of filters. They identified cannabis smoke as a carcinogen and also said awareness of the danger was low compared with the high awareness of the dangers of smoking tobacco particularly among younger users. They said there was an increased risk from each cannabis cigarette due to drawing in large puffs of smoke and holding them.

In 2013 the International Lung Cancer Consortium found no significant additional lung cancer risk in tobacco users who also smoked cannabis. Nor did they find an increased risk in cannabis smokers who did not use tobacco. They concluded that "Our pooled results showed no significant association between the intensity, duration, or cumulative consumption of cannabis smoke and the risk of lung cancer overall or in never smokers." They cautioned that "Our results cannot preclude the possibility that cannabis may exhibit an association with lung cancer risk at extremely high dosage."

Head and neck cancer

Infrequent marijuana smoking is not believed to increase risk of head and neck malignancies.

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Long-term effects of cannabis" – news · newspapers · books · scholar · JSTOR (December 2013) (Learn how and when to remove this message)

Gordon and colleagues (2013) said there was a risk of these cancers associated with marijuana use over a long period of time.

Respiratory effects

According to a 2013 literature review by Gordon and colleagues, inhaled marijuana is associated with lung disease.

Of the various methods of cannabis consumption, smoking is considered the most harmful; the inhalation of smoke from organic materials can cause various health problems (e.g., coughing and sputum). Isoprenes help to modulate and slow down reaction rates, contributing to the significantly differing qualities of partial combustion products from various sources.

A 2012 literature review by the British Lung Foundation found lack of research on the effect of cannabis smoke alone due to common mixing of cannabis and tobacco and frequent cigarette smoking by cannabis users; a low rate of addiction compared to tobacco; and an episodic nature of cannabis use compared to steady frequent smoking of tobacco.

Reproductive and endocrine effects

Cannabis consumption in pregnancy is associated with restrictions in growth of the fetus, miscarriage, and cognitive deficits in offspring. Although the majority of research has concentrated on the adverse effects of alcohol, there is now evidence that prenatal exposure to marijuana and cocaine has serious effects on the developing brain and is associated with "deficits in language, attention, areas of cognitive performance, and delinquent behavior in adolescence". A report prepared for the Australian National Council on Drugs concluded cannabis and other cannabinoids are contraindicated in pregnancy as it may interact with the endocannabinoid system.

Mortality

No fatal overdoses associated with cannabis use have been reported. The evidence is insufficient to show an elevated risk of mortality from all causes (including suicide) among cannabis users, although some studies imply that motor vehicle fatalities, and possibly respiratory and brain cancers, may have a higher risk among heavy users.

See also

• Medical cannabis
• Effects of cannabis
• Cannabinoid hyperemesis syndrome

References

1. "Medical Marijuana Policy in the United States". Stanford.edu. 2012-05-15. Retrieved 2013-01-15.
2. ^ Gordon AJ, Conley JW, Gordon JM (2013). "Medical consequences of marijuana use: a review of current literature". Curr Psychiatry Rep (Review). 15 (12): 419. doi:10.1007/s11920-013-0419-7. PMID 24234874. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
3. Grotenhermen, F; Müller-Vahl, K (2012). "The therapeutic potential of cannabis and cannabinoids". Deutsches Ärzteblatt International. 109 (29–30): 495–501. doi:10.3238/arztebl.2012.0495. PMC 3442177. PMID 23008748. {{cite journal}}: Unknown parameter |month= ignored (help)
4. Borgelt LM, Franson KL, Nussbaum AM, Wang GS (2013). "The pharmacologic and clinical effects of medical cannabis". Pharmacotherapy (Review). 33 (2): 195–209. doi:10.1002/phar.1187. PMID 23386598. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
5. Danovitch I, Gorelick DA (2012). "State of the art treatments for cannabis dependence". Psychiatr. Clin. North Am. (Review). 35 (2): 309–26. doi:10.1016/j.psc.2012.03.003. PMC 3371269. PMID 22640758. {{cite journal}}: Unknown parameter |month= ignored (help)
6. ^ Parakh, P; Basu, D (2013). "Cannabis and psychosis: have we found the missing links?". Asian Journal of Psychiatry (Review). 6 (4): 281–7. doi:10.1016/j.ajp.2013.03.012. PMID 23810133. {{cite journal}}: Unknown parameter |month= ignored (help)
7. ^ Niesink, RJ; van Laar, MW (2013). "Does Cannabidiol Protect Against Adverse Psychological Effects of THC?". Frontiers in Psychiatry (Review). 4: 130. doi:10.3389/fpsyt.2013.00130. PMC 3797438. PMID 24137134.{{cite journal}}: CS1 maint: unflagged free DOI (link)
8. Barceloux, Donald G (20 March 2012). "Chapter 60: Marijuana (Cannabis sativa L.) and synthetic cannabinoids". Medical Toxicology of Drug Abuse: Synthesized Chemicals and Psychoactive Plants. John Wiley & Sons. p. 901. ISBN 978-0-471-72760-6.
9. Rathbone, John; Variend, Hannele; Mehta, Hetal (2008). Rathbone, John (ed.). "Cannabis and schizophrenia". Cochrane Database Systematic Review (Review) (3): CD004837. doi:10.1002/14651858.CD004837.pub2. PMID 18646115. {{cite journal}}: Unknown parameter |subscription= ignored (|url-access= suggested) (help)
10. Chadwick, Yasmin L; Miller; Hurd (2013). "Cannabis Use during Adolescent Development: Susceptibility to Psychiatric Illness". Frontiers in Psychiatry (Review). 4: 129. doi:10.3389/fpsyt.2013.00129. PMC 3796318. PMID 24133461.{{cite journal}}: CS1 maint: unflagged free DOI (link)
11. Scuderi, C; Filippis, DD; Iuvone, T; Blasio, A; Steardo, A; Esposito, G (2009). "Cannabidiol in medicine: a review of its therapeutic potential in CNS disorders". Phytotherapy Research : PTR (Review). 23 (5): 597–602. doi:10.1002/ptr.2625. PMID 18844286. {{cite journal}}: Unknown parameter |month= ignored (help)
12. ^ "Evidence-based answers to cannabis questions: a review of the literature" (PDF). Canberra: Australian National Council on Drugs. 2006. {{cite web}}: Unknown parameter |authors= ignored (help)
13. Attention: This template ({{cite pmid}}) is deprecated. To cite the publication identified by PMID 12107710, please use {{cite journal}} with |pmid=12107710 instead.
14. ^ Calabria B, Degenhardt L, Hall W, Lynskey M (2010). "Does cannabis use increase the risk of death? Systematic review of epidemiological evidence on adverse effects of cannabis use". Drug Alcohol Rev (Review). 29 (3): 318–30. doi:10.1111/j.1465-3362.2009.00149.x. PMID 20565525. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
15. Bilkei-Gorzo A (2012). "The endocannabinoid system in normal and pathological brain ageing". Philos. Trans. R. Soc. Lond., B, Biol. Sci. (Review). 367 (1607): 3326–41. doi:10.1098/rstb.2011.0388. PMC 3481530. PMID 23108550. {{cite journal}}: Unknown parameter |month= ignored (help)
16. Kazuhide H, Mishima K, Fujiwara M (2010). "Therapeutic potential of non-psychotropic cannabidiol in ischemic stroke". Pharmaceuticals (Review). 3 (7): 2197–2212. doi:10.3390/ph3072197.{{cite journal}}: CS1 maint: multiple names: authors list (link) CS1 maint: unflagged free DOI (link)
17. Abadinsky, H. (2004). Drugs: An Introduction (5th ed.). pp. 62–77, 160–166. ISBN 0-534-52750-7.
18. Attention: This template ({{cite pmid}}) is deprecated. To cite the publication identified by PMID 4441242, please use {{cite journal}} with |pmid=4441242 instead.
19. Attention: This template ({{cite pmid}}) is deprecated. To cite the publication identified by PMID 18482420, please use {{cite journal}} with |pmid=18482420 instead.
20. Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1093/aje/kwr200, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi=10.1093/aje/kwr200 instead.
21. Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1016/j.amjmed.2013.03.002, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi=10.1016/j.amjmed.2013.03.002 instead.
22. Attention: This template ({{cite pmid}}) is deprecated. To cite the publication identified by PMID 18378995, please use {{cite journal}} with |pmid=18378995 instead.
23. Parolaro, D; Massi, P (2008). "Cannabinoids as potential new therapy for the treatment of gliomas". Expert review of neurotherapeutics. 8 (1): 37–49. doi:10.1586/14737175.8.1.37. PMID 18088200.
24. "Smoking Marijuana Tied to Testicular Cancer". WebMD. 9 September 2012. Retrieved November 2013. {{cite web}}: Check date values in: |accessdate= (help)
25. Tomar, Rajpal C. (2009). "Evidence on the carcinogenicity of marijuana smoke" (PDF). Reproductive and Cancer Hazard Assessment Branch Office of Environmental Health Hazard Assessment, California Environmental Protection Agency. Retrieved 2012-06-23. {{cite web}}: Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |month= ignored (help)
26. ^ "The impact of cannabis on your lungs". British Lung Association. 2012. Retrieved 2013-01-09. {{cite web}}: Unknown parameter |month= ignored (help)
27. Zhang R, Zuo-Feng Z, Morgenstern H; et al. (15). "Abstract 3633: Cannabis smoking and lung cancer risk: pooled analysis in the International Lung Cancer Consortium". Cancer Research. 73 (8). {{cite journal}}: Check date values in: |date= and |year= / |date= mismatch (help); Explicit use of et al. in: |author= (help); Unknown parameter |laydate= ignored (help); Unknown parameter |laysource= ignored (help); Unknown parameter |layurl= ignored (help); Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
28. Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi: 10.1300/J175v01n03_09, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi= 10.1300/J175v01n03_09 instead.
29. Attention: This template ({{cite pmid}}) is deprecated. To cite the publication identified by PMID 16128224, please use {{cite journal}} with |pmid=16128224 instead.
30. Fonseca BM, Correia-da-Silva G, Almada M, Costa MA, Teixeira NA (2013). "The Endocannabinoid System in the Postimplantation Period: A Role during Decidualization and Placentation". Int J Endocrinol (Review). 2013: 510540. doi:10.1155/2013/510540. PMC 3818851. PMID 24228028.{{cite journal}}: CS1 maint: multiple names: authors list (link) CS1 maint: unflagged free DOI (link)
31. Irner TB (2012). "Substance exposure in utero and developmental consequences in adolescence: a systematic review". Child Neuropsychol (Review). 18 (6): 521–49. doi:10.1080/09297049.2011.628309. PMID 22114955.

• Cannabis