Home > Consequences of cannabis use.

Connolly, Johnny (2004) Consequences of cannabis use. Drugnet Ireland, Issue 12, December 2004, pp. 7-8.

PDF (Drugnet Ireland, issue 12) - Published Version

The National Advisory Committee on Drugs recently published An overview of scientific and other information on cannabis. The report draws on relevant research from Ireland and abroad with a view to presenting a balanced account of how this illegal but widely used substance affects a range of outcomes. The review was conducted by four authors, from four different disciplines.

The pharmacological and toxicological effects of cannabis were considered by Dr Dominique Crowley. The identification through laboratory studies of two cannabis receptors in the brain, linked to memory, movement and co-ordination, pain perception and the reward system, has resulted in a better understanding of cannabis effects in humans. The potential therapeutic value of cannabis compounds is difficult to assess, as a specific ‘dose’ of cannabis cannot be reliably administered. There is only anecdotal evidence to suggest that cannabis may have beneficial effects on mood disorders, but cannabis and its derivatives can be useful in the treatment of pain and nausea. There is a strong association between cannabis use and some mental health problems; people suffering from a depressive condition are much more likely to become heavy users of the drug than those without such a diagnosis.

Dr Crowley also examined the connection between cannabis use and short-term memory loss, cardiac problems and respiratory conditions. Evidence of a link between cannabis use and cancer and antenatal health problems has not been firmly established.

Dr Claire Collins reviewed the epidemiological evidence concerning the public health risks of the drug. Prevalence rates for cannabis use are highest among the 15–24 year age group, with over three-quarters of 16-year-olds saying they know where to obtain the drug and relatively low proportions perceiving cannabis use as risky behaviour. In about 80 per cent of cases, young people try out cannabis for the first time with their friends.

There is a strong statistical association between cannabis use during adolescence and subsequent use of other illicit drugs. However, most young people who try cannabis do not progress to either heavy cannabis use or the use of other illicit drugs. Another public health consequence of cannabis use is its association with traffic accidents, where it can often combine with alcohol as a contributory factor.

Dr Mark Morgan examined the psychological consequences of cannabis use. While there is little evidence that cannabis use has an impairing effect on cognitive functioning as measured by IQ tests, heavy cannabis use produces subtle cognitive impairments of memory, attention and the organisation of complex information.

It is often suggested that cannabis induces ‘amotivational syndrome’ where users appear to be apathetic, lethargic and unmotivated. However, recent studies have failed to find clear-cut evidence for this syndrome. A strong association between cannabis use and poor educational outcomes is a firmly established finding in the literature.

There is consistent evidence that young people attempting suicide are more likely to have a history of heavy cannabis use than are others. However, personality make-up and the presence of other substances must be considered when attempting the to define the contributory role of cannabis.

Mr Johnny Connolly examined the criminological and sociological consequences of cannabis use. Many of the negative criminological and sociological consequences related to cannabis have been attributed to its legal status, rather than to any properties of the drug itself. The debate over cannabis law reform remains one of the most contested areas of international drug policy. The legal status of cannabis has come under increased scrutiny in recent years in Ireland. The National Crime Forum, established by the Minister for Justice, Equality and Law Reform in 1998, heard arguments for and against the decriminalisation of cannabis.1 The recent declassification of cannabis in the United Kingdom has contributed to further debate on the subject.2

Cannabis is the most widely trafficked drug globally. In Ireland, as in most other countries, there are more seizures of cannabis than of any other drug. In 2002, cannabis-related seizures accounted for 54 per cent of the total number of drug seizures for that year and An Garda Síochána figures show a steady increase in the total number of cannabis-related offences in recent years.3 Cannabis-related offences accounted for 64 per cent of the total number of offences in which criminal proceedings commenced in 2002.

This section also looks at the effect that drug laws have had on educational and employment prospects, relationships and travel in a number of countries. Cannabis laws can contribute to marginalisation and alienation, inducing a perspective among young people that the law is unfair, heavy-handed and out of touch.

It is difficult to establish the precise causative link between drug use and crime, aside from the obvious link to drug offences such as possession and supply. Recent studies have found an association between heavy use by juveniles and aggressive behaviour. A recent UK review concluded that those who use illicit drugs are more likely to be involved in crime, and vice versa. Although there is clear evidence of violence associated with the drug trade, in the absence of any adequate studies into Irish drug markets it is impossible to state with any clarity the extent to which violence is associated specifically with the trade in cannabis.

The gateway theory holds that, although most cannabis users do not progress to other drugs, cannabis primes the user into taking other illicit drugs, either through a physiological mechanism or through personality and social factors. Among the factors which have been identified as increasing the probability of further harm are early onset of cannabis use, family and other problems, and exposure to other illicit drug markets, and alcohol and tobacco consumption. Age and gender are also important factors.

Many countries have sought to address the gateway factor by introducing changes in cannabis law enforcement practices or through legal reforms. The chapter concludes by highlighting the need for further research in the drugs–crime area in Ireland. There is a particular need for more data describing the way in which laws are being implemented in the area of drug markets.

1 Government of Ireland (1998) National Crime Forum Report. Dublin: Institute of Public Administration.
2 For an analysis of the legal changes in the UK see Connolly J (2004) Reclassification of cannabis in the UK, Drugnet Ireland, Issue 10, March 2004.
3 An Garda Síochána Annual Reports for 2000, 2001, 2002 and 2004. Dublin: Stationery Office.

Item Type
Publication Type
Irish-related, Open Access, Article
Drug Type
Issue Title
Issue 12, December 2004
December 2004
Page Range
pp. 7-8
Health Research Board
Issue 12, December 2004
Accession Number
HRB (Available)

Repository Staff Only: item control page