Posts by Ross Bell
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Regardless the findings from the evidence cited above re mental health etc, I think most can agree our 35-year-long faith in our Misuse of Drugs Act to eliminate those harms has been seriously misplaced.
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Sorry, me again with the research evidence (from the same The Lancet source):
Cannabis use has been associated with increased risk of psychiatric disorders. A 15-year follow-up of 50,465 Swedish male conscripts reported that those who had tried cannabis by age 18 years were 2-4 times more likely to be diagnosed with schizophrenia than those who had not. Risk increased with the frequency of cannabis use and remained significant after statistical adjustment for a few confounding variables. Those who had used cannabis ten or more times by 18 years of age were 2·3 times more likely to be diagnosed with schizophrenia than those who had not. Zammit and colleagues reported a 27-year follow-up of the same cohort. These investigators also showed a dose–response relation between frequency of cannabis use in individuals aged 18 years and risk of schizophrenia during the follow-up, and this association persisted after controlling for the effects of other confounding factors. They estimated that 13% of schizophrenia cases could be averted if cannabis use was prevented. These findings have been supported by longitudinal studies in the Netherlands, Germany, and New Zealand all of which indicated that the association persisted after adjustment for confounders.
A meta-analysis of these longitudinal studies reported a pooled OR of 1·4 (95% CI 1·20–1·65) of psychotic symptoms or psychotic disorders in those who had ever used cannabis. Risk of psychotic symptoms or disorders was higher in regular users than in non-users (OR 2·09, 95% CI 1·54–2·84). Reverse causation was addressed in most of these studies by exclusion of cases reporting psychotic symptoms at baseline or by statistically adjusting for pre-existing psychotic symptoms. The common causal hypothesis was difficult to exclude because the association between cannabis use and psychosis was attenuated after statistical adjustment for potential confounders, and no study assessed all major confounders.
Evidence is conflicting on whether incidence of schizophrenia increases as cannabis use increases in young adults, as would be expected if the association was causal. An Australian study did not show clear evidence of increased psychosis incidence despite steep increases in cannabis use during the 1980s and 1990s. A similar study suggested that it was too early to see any increased incidence in England and Wales in the 1990s. A British and a Swiss study reported increases in the incidence of psychoses in recent birth cohorts but another British study failed to do so.
Non-consistent and weak associations have been reported between cannabis use and depression. Fergusson and Horwood, for example, found a dose–response relation between frequency of cannabis use in individuals aged 16 years and depressive disorder, but the association was not significant after adjusting for confounders. A meta-analysis of these studies reported an association between cannabis use and depressive disorders (OR 1·49, 95% CI 1·15–1·94). The investigators argued, however, that these studies had not controlled for confounders and had not convincingly excluded the possibility that depressed young people are more likely to use cannabis.
Several case–control studies have shown a relation between cannabis use and suicide in adolescents, but whether this is causal is unclear. For example, a New Zealand case–control study of serious suicide attempts resulting in hospitalisation found that 16% of the 302 people attempting suicide met criteria for cannabis dependence or abuse compared with 2% of the 1028 community controls. Controlling for social disadvantage, depression, and alcohol dependence substantially reduced, but did not eliminate, the association (OR 2).
The evidence from prospective studies is mixed. Fergusson and Horwood, for example, found a dose– response relation between frequency of cannabis use in individuals aged 16 years and a self-reported suicide attempt, but the association did not persist after controlling for confounders. Patton and colleagues reported that cannabis was associated with self-harmful behaviour in women but not in men, after controlling for depression and alcohol use. A meta-analysis reported that these studies were too heterogeneous to estimate risk, and few had excluded reverse causation or properly controlled for confounding.
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Apologies - I'm posting below a summary of research on cannabis and health (Adverse health eff ects of non-medical cannabis use. Wayne Hall, Louisa Degenhardt. The Lancet 2009 - not available online - but I can send interested folks the full PDF - email me ross.bell@drugfoundation.org.nz)
Regular cannabis smokers report more symptoms of chronic bronchitis (wheeze, sputum production, and chronic coughs) than do non-smokers.
The immunological competence of the respiratory system in cannabis-only smokers is also impaired, increasing their health service use for respiratory infections.
A longitudinal study of 1037 young people in New Zealand followed until the age of 26 years found impaired respiratory function in cannabis-dependent users, but this finding was not replicated in longer-term follow-up of US users.
Chronic cannabis smoking did not increase the risk of emphysema in follow-up studies over 8 years in cannabis-only smokers in the USA and New Zealand.
Cannabis smoke contains many of the same carcinogens as does tobacco smoke, with some in higher concentrations. It is also mutagenic and carcinogenic in the mouse skin test, and chronic cannabis smokers show pathological changes in lung cells that precede the development of lung cancer in tobacco smokers.
Epidemiological studies have not consistently reported increased risks of upper respiratory tract cancers. Sidney and colleagues studied cancer incidence in an 8•6-year follow-up of 855 members of the Kaiser Permanente Medical Care Program. They showed no increased risk of respiratory cancer in current or former cannabis users.
Zhang and colleagues reported an increased risk (OR 2) of squamous cell carcinoma of the head and neck in cannabis users in 173 cases and 176 controls that persisted after adjusting for cigarette smoking, alcohol use, and other risk factors. Three other case–control studies of these cancers, however, have failed to find any such association.
Case–control studies of lung cancer have produced more consistent associations with cannabis use but their interpretation is uncertain because of confounding by cigarette smoking.
A Tunisian case–control study of 110 cases of hospital-diagnosed lung cancer and 110 community controls indicated an association of lung cancer with cannabis use (OR 8•2) that persisted after adjustment for cigarette smoking. A pooled analysis of three Moroccan case–control studies also showed an increased risk of lung cancer in cannabis smokers, all of whom also smoked tobacco.
A New Zealand case–control study of lung cancer in 79 adults under the age of 55 years and 324 community controls found a dose–response relation between frequency of cannabis use and lung cancer risk. A US case–control study showed a simple association between cannabis smoking and head and neck and lung cancers, but these associations were not significant after controlling for tobacco use.
Larger cohort and better designed case–control studies are needed to clarify whether any such risks from chronic cannabis smoking exist.
Evidence exists to support the adverse cardiovascular effects of cannabis use. Cannabis and THC increase heart rate in a dose-dependent way. These drugs marginally affect healthy young adults who quickly develop tolerance, but concern exists about adults with cardiovascular disease.
A case-crossover study by Mittleman and colleagues of 3882 patients who had had a myocardial infarction showed that cannabis use can increase the risk of myocardial infarction 4•8 times in the hour after use. A prospective study of 1913 of these individuals reported a dose–response relation between cannabis use and mortality over 3•8 years. Risk increased 2•5 times for those who used cannabis less than once a week to 4•2 times in those who used cannabis more than once a week. These findings are supported by laboratory studies that indicate that smoking cannabis provokes angina in patients with heart disease.
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The general consensus on legal status of drugs and use (see my earlier reference of the Cannabis Commission) is that there appears to be no apparent link between cannabis policy - whether liberal or draconian - and prevalence of use. But that, by contrast, policy actions can certainly affect the adverse social consequences arising from the law and its enforcement.
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The same debate, but on YouTube!
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Stephen or anyone else -- can we crowdsource this? -- feel free to post those links in comments.
Rather than go hunting down all those citations, I'd recommend this recent report (Beckley Foundation's Cannabis Commission) for probably the best and most recent review of cannabis harm literature: that's both harm from pot, and from the system "controlling" pot.
Good to see NORML beginning to get their ideas out there now as we head towards a major review of our drug law - but Stephen, I don't think your analysis is quite there yet (as previous comments above note - the alcohol v cannabis argument has its flaws).
And it's probably time NORML detailed what it means by "legalisation".
Ross Bell, NZ Drug Foundation
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Wow, there's a whole new world opening up for me. Thanks Sean.
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Sean's site is more user-friendly than this one http://www.craftown.com/xmas.htm
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I would quite like to see this bus advertisement campaign - Nice People Take Drugs - but it's been pulled from London buses.
You can still get the t-shirt and pack of cards.
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Am I missing something? LTSA seem to have removed the ad from their site.
It does appear to have been removed. The radio ads too.
Russell, now look what you've done!