Analysis: characteristics of frequent and high-risk cannabis users
Cannabis is Europe’s most commonly used illicit drug, with approximately 20 million adults, or around 6% of the population aged 15–64 years, having used the drug in the last year. An indication of the public health impact of the drug can be seen in the numbers entering specialised treatment in Europe for drug-related problems, among whom cannabis is the second most frequently reported drug, after heroin. Against this backdrop, identifying the characteristics of frequent and high-risk cannabis users can help with the identification and design of interventions for those cannabis users most at risk of experiencing problems.
This analysis uses two main data sources to explore frequent and high-risk cannabis use in Europe. First, general population surveys provide data on frequency of cannabis use. Secondly, data collected by specialised drug treatment centres on clients entering treatment for problems primarily related to cannabis use give insight into the personal and social characteristics of this group of users, a high proportion of which may be engaging in high-risk patterns of cannabis use. Additional information is derived from the literature.
Frequent and high-risk cannabis use in Europe: prevalence of the phenomenon
Any description of intensive forms of cannabis use is complicated by a lack of consensus on the terminology. For monitoring purposes, the EMCDDA uses ‘daily or near-daily use’ (use on 20 days or more in a month), which is also referred to as ‘frequent cannabis use’. High-risk cannabis use is defined as ‘cannabis use disorder’, as described in the current international diagnostic manuals (i.e. ICD and DSM). This includes, in particular, cannabis dependence.
The most recent EMCDDA estimate suggests that there are just below 1% of daily or almost daily cannabis users among citizens of EU, Norway and Turkey aged 15–64 (EMCDDA, 2015). Additional information can be found in youth surveys which monitor the prevalence of more intensive cannabis use (40 or more times in life) in 15- to 16-year-old school students. Prevalence of intensive use in this group ranges from 0.3% to 8%, depending on the country.
Data on users entering drug treatment for cannabis-related problems can also shed some light on high-risk cannabis use in Europe. Among clients who entered drug treatment for the first time in their life in 2011, cannabis use is the most frequently cited reason – and has been since 2008. The number of first-time cannabis clients has risen markedly, mainly since 2008. Currently, cannabis clients represent around half or more of all clients entering drug treatment in five countries (France, Denmark, Cyprus, Hungary and the Netherlands). Country differences in levels of treatment demand need to be interpreted with caution, however, and may reflect differences in treatment provision, referral practices, legislation, in addition to the prevalence of intensive cannabis use. For example, referrals from the criminal justice system may blur the picture by introducing into the treatment system cannabis users with less frequent patterns of use.
Males particularly over-represented among frequent and high-risk cannabis users
Males are generally over-represented among cannabis users, and their share in the cannabis-using population has what is known as a ‘dose-dependent relationship’ with frequency of use and related problems. This means that the proportion of males increases with frequency of cannabis use, and is highest among those with problems related to cannabis (here represented by users entering treatment). So, while approximately 70% of last year cannabis users are male, the proportion of males rises to 75% among last month users, 78% among daily users in the last month and 84% among treatment entrants reporting cannabis as their primary drug (see Table 1). Over-representation of males among users is typical for illicit drugs; however, cannabis clients present one of the highest ratios of males to females among drug clients entering treatment. Although there is some variation between countries, nearly all report that three-quarters or more of cannabis treatment entrants are male.
Table 1: Gender breakdown according to frequency of cannabis use among adults (15–64 years) and treatment entrants reporting cannabis as their primary drug
|(1) Age range among treatment entrants might be slightly broader than 15–64 years.Source: EMCDDA Statistical bulletin, 2013
||Use of cannabis at least once in the last year
||Use of cannabis at least once in the last month
||Daily cannabis users
||Cannabis users entering treatment (1)
The literature highlights a number of important issues for women with daily or dependent cannabis use: for example, these women are significantly more likely to have a cannabis-using partner, but less likely to have a heavy cannabis-using social network. With similar patterns of cannabis use, they have greater concern about their cannabis use and perceived difficulty of quitting (Copeland et al., 2001; Swift et al., 2000). Males with similar patterns of use, in contrast, tend to have higher levels of alcohol and tobacco use, more criminal convictions and higher levels of psychosocial distress (Copeland et al., 2001).
Cannabis clients among the youngest in treatment
Frequent and high-risk cannabis users tend to be young people (below 35 years of age). Of the estimated 3 million European daily cannabis users, roughly 70% are aged between 15 and 34, and over 86% of clients entering treatment in Europe with cannabis as their primary drug are aged 34 or less. The estimated mean age of clients entering treatment for cannabis use is 25 years, which is one of the lowest mean ages among the different groups of drug clients.
Populations of older cannabis users do exist. Studies available on users who have been using the drug for 10 or more years (on average 19) suggest that they may have established a routine of cannabis use that is less intensive than that of younger frequent users. Various reasons are suggested to explain why older users may feel less inclined to discontinue their cannabis smoking: for example, they may perceive more benefits than risks from their use or experience less social pressure to stop (Korf et al., 2007; Reilly et al., 1998). As a consequence, this group may be less likely to contact services, even though problems such as cannabis dependence are not uncommon among these users (Swift et al., 2000).
The majority of frequent cannabis users will have started to use the drug while they were in their teens. The age at first use is negatively associated with the level of harm potentially experienced by the user. Early initiation and regular cannabis use during adolescence have been found to be associated with numerous negative outcomes, including problematic patterns of cannabis use, use of other illicit drugs, mental health problems and low educational achievement (Copeland and Swift, 2009; Fischer et al., 2011). It is important not to infer that early cannabis use causes all the above-mentioned harms, as there are numerous common and overlapping risk factors and life experiences that may explain this association.
Socio-economic status: diverse findings
Data on the socio-economic status of frequent cannabis users are scarce and sometimes contradictory. A recent Dutch study (van der Pol et al., 2013) found frequent cannabis users to have, on average, a higher level of educational attainment than the general population; however, they were more often unemployed or unable to work. In two Australian studies (Copeland et al., 2001; Reilly et al., 1998), community samples of heavy or long-term cannabis users had levels of educational attainment and employment similar to or higher than those of the general population. A 2012 analysis of EU treatment demand data found that 87% (ranging from 50% to 98% between countries) of the cannabis users entering treatment were living in stable accommodation. 60% have completed at least secondary education again with variation by country, while almost half (47%) were in full-time education or employment. Unemployment among primary cannabis users entering treatment stood at 38.5% and ranged from 12% in Lithuania to 53% in Ireland and 65% in Turkey.
A study among French adolescents supports the view that higher socio-economic status has a protective effect against daily cannabis use (Legleye et al., 2011). Findings suggest that although young people from families with higher socio-economic status had higher risk of experimental use of cannabis, they were also less likely to engage in daily use of the drug.
This exploration of the evidence on the characteristics of frequent cannabis users supports the findings of studies which identify young males as a population group that is over-represented among frequent cannabis users. Among frequent and daily users of cannabis, dependence is a concern and may help to explain some of the variation that exists in patterns of use, mental health and cannabis-related problems (see panel 4). With regard to the design of appropriate interventions for users most at risk of experiencing problems, evidence presented here suggests that these should be suited to predominantly young male populations with high levels of cannabis-related problems, poly-drug use patterns and likely mental health problems. Treatment options should take into account the significant minority of women among those with cannabis problems, as they may have different needs. Looking towards the future, treatment services may see growing numbers of older cannabis users, if a sizeable proportion of the current relatively large population of frequent cannabis users continue to use the drug intensively as they age.
Characteristics of frequent cannabis users with and without dependence
A small number of studies have looked into the concept of cannabis dependence, comparing frequent (1) or daily cannabis users with and without dependence (Looby and Earleywine, 2007; van der Pol et al., 2013), or populations with self-perceived treatment need to populations without this perception (Copeland et al., 2001). Depending on the population studied, somewhere between 25% and 50% of daily cannabis users will fulfil the criteria for dependence (NIDA, 2012). A general conclusion that can be drawn from these studies is that, while frequent to daily use of cannabis is a strong predictor of cannabis-related problems (Fischer et al., 2011), these accumulate even more in users with (probable) dependence.
Although the above-mentioned studies have found relatively small differences in the frequency or intensity of use or quantity of cannabis used between dependent and non-dependent frequent or daily users, marked differences were identified between dependent and non-dependent users in the levels of cannabis-related problems experienced, use of other substances and mental health problems. Other characteristics more prevalent in dependent users included solitary use and use in order to cope with problems.
In a recent study among a sample of Dutch cannabis users, frequent users (with and without dependence) had a higher prevalence of externalising disorders such as childhood and adult attention deficit-hyperactivity disorder or conduct disorder (van der Pol et al., 2013). This association was stronger in those with cannabis dependence. They had, in addition, an increased prevalence of internalising disorders, such as depression or anxiety disorder. These mental health problems are often preceded by childhood adversity, and factors such as loss of parent or child abuse were relatively common in both groups, and more common than in the general population.
Childhood adversity, however, did not explain the differences in mental health between dependent and non-dependent users. The authors concluded that there must be other, personality-related, genetic or environmental vulnerability factors that play a role. It is probable that these factors are involved both in mental health problems and cannabis dependence.