Patterns of cannabis use in Amsterdam among experienced cannabis users

Some preliminary data from the 1995 Amsterdam Cannabis Survey

Introduction

In 1995 and in 1996 we interviewed experienced cannabis users in Amsterdam, Utrecht and Tilburg. In this paper we will discuss only some results obtained from the Amsterdam sample.

The Amsterdam sample of experienced cannabis users was found by using the data from a household survey we had conducted in 1994 to measure drug use in the population of Amsterdam of 12 years and older. In order to measure drug use in the population we accessed a net random sample of 4,363 persons that was taken from the Municipal Registry. For a full description of the population sampling and survey methodology see Sandwijk et al., 1995. Among the respondents in the 1994 population survey we found 1,272 (29.2 percent) persons who had used hashish or marihuana at least once in their lifetime.

Out of the pool of all cannabis users we found in the Amsterdam population, we invited those that had used marijuana or hashish at least 25 times in their lifetime to participate in an in depth cannabis survey. This level of cannabis use was reached by 536 respondents out of the group of 1,272 cannabis users, that is 42,1 percent of all cannabis users, or 12.3 percent of the population. Of these 536 experienced users, 251 persons were willing to participate and returned to us a signed consent form. During the year 1995 we managed to track down and interview a total of 216 persons. The other 34 persons either refused us an interview despite an earlier promise to participate, or could not be traced due to moving to an unknown address or a long stay abroad.

We compared the 216 experienced cannabis users we interviewed with the 319 we did not, on 8 variables. This showed that there were no statistically significant differences between the two groups on 7 variables: gender, age, type of household, type of employment, income, prevalence of cannabis use (during last year and during last thirty days prior to interview), length of cannabis use career and the use of other drugs. The response group however has a slight but statistically significant higher level of education than the non response group. Although this difference might be relevant it is insufficient to conclude that the response group is not representative for experienced cannabis users in the population sample.[1]

Here we will describe some characteristics of the group of 216 experienced cannabis users we interviewed in 1995. We focused on these experienced users because we wanted to examine in depth many aspects of cannabis use, something that would be hard or impossible if we would interview users that had had only fleeting experience with the substance.[2] The majority (56.3 percent) of those in our population sample who ever had tried hashish or marijuana, only used it less than 25 times and then decided not to use it anymore.[3] We considered this a level of cannabis experience that would yield insufficient data on effects and consequences of cannabis use.

Also important to notice is the fact that all respondents live in Amsterdam. The population of Amsterdam differs from the rest of the Netherlands due to the nature of the city. Amsterdam is the cultural and financial capital of the Netherlands with two universities, theatres, orchestras, banking headquarters and financial and information services, a large and expanding seaport, and thousands of cafés and restaurants. This undoubtedly has some impact on the type of inhabitants that come to live in the city. The overall picture of drug use in Amsterdam is therefor quite probably not representative for drug use in the Netherlands.

Initiation into cannabis use

The average age on which the experienced cannabis users we interviewed tried hashish or marijuana for the first time is 16.9 years. This is over 3 years earlier than the average age of onset of 21 years we computed for the 709 persons in the population survey who reported a life time experience with cannabis of less than 25 times. The average age of our respondents at time of interview was 34 years. The average length of cannabis use career of our respondents who had quitted cannabis was 10 years. The average length of cannabis use career of the respondents who still used hashish or marijuana was 13.7 years.

Figure 1 shows the age of first cannabis use by sex. More than 96 percent of our respondents had started their cannabis use before the age of 25. Between men and women age of onset does not differ significantly. However, there are slight differences in the way men and women obtain their first cannabis.

Figure 1. Age of first cannabis use among experienced cannabis users

Only four women (4.5 percent) bought their first hashish or marihuana. The others were initiated by cannabis they received from friends. Of the men, 18 percent bought their first cannabis. However, for both women and men we observe a large majority who does not buy first cannabis. There is no difference in having asked for hashish or marihuana in order to initiate use between men and women.

Developments in cannabis use

The onset of cannabis use is clearly linked to young adulthood, but how does the use of cannabis develop after initiation? In our survey we asked many questions to trace aspects of use pattern development. One of the ways to establish a pattern of use was to confront our respondents with simple graphs that represented six possible ways of development of cannabis use.

Figure 2. Theoretical patterns of development in cannabis use

1. First much - slowly less. The respondent starts using large amounts after he or she first tried marijuana or hashish but gradually decreased since then. This pattern of cannabis use was reported by 17 respondents (7.8%).
2. Slowly more. The respondents' marijuana use has gradually increased over the years. This pattern of cannabis use was reported by 13 respondents (6.0%).
3. Stable. The respondent started using marijuana or hashish at the same level that he or she still uses, and the amount and frequency have not changed. This pattern was reported by 25 respondents (11.5%).
4. Up - top - down. The respondents' use increased gradually until it reached a peak, then it decreased. This is the pattern of cannabis use that was reported most frequently. Almost half of the respondents (104, 47.9%) said that this pattern resembled their own cannabis using career.
5. Intermittent. The respondent has started and stopped using marijuana or hashish many times. This is the least reported pattern. Only 7 respondents (3.2%) reported this pattern.
6. Varying. The respondents' use pattern has varied considerably over the years. This pattern was reported by 51 respondents (23.5%) and is the second most frequently reported pattern.

More than half of the respondents report a decreasing level of cannabis use during their career. Only six percent reports an increase. What this looks in terms of levels or amounts of use we show in Figure 3. In this graph we show level of use in three periods in a cannabis user's career:

1. the initial year of regular use,
2. the period of heaviest cannabis use, and
3. the last three months prior to the interview.

Figure 3. Levels of cannabis use over time (number of respondents between brackets, N = 216)

Level of cannabis use is defined in grams per month. We defined a low level of use as up to 2.5 grams of hashish or marihuana per month, a medium level between 2.5 and 10 grams per month, and a high level of cannabis use is defined as more than 10 grams per month.

Almost 54% of the experienced cannabis users report to have raised their level of use during some part of their career, with 33% reaching a high level during the period of maximum consumption (top period of use). Sustained high level of use is rare, as is clearly shown in Figure 3. We also show that the amounts of cannabis one consumes in the beginning of ones career, does not say much about the probability of being abstinent at time of interview. 'High level starters' are as likely to bring their cannabis use down to zero as 'low level starters'. Of 216 respondents, half did not use any cannabis during the last three months prior to the interview. Another 29 percent used at a low level. High levels of use during the last three months prior to the interview were rare (5.5 percent).

Decreasing and quitting cannabis use

It is clear that during their career most cannabis users report decreasing levels of use or quit altogether. There are two main explanations for this.

The first explanation is progressing to another stage in life. As said earlier, the onset of cannabis use is clearly associated with young age. Of all respondents, 96 percent had started their cannabis use before the age of 25. Quitting or decreasing one's cannabis use is related to growing older and marks the evolution to a different lifestyle that is associated with a steady partner, children perhaps, getting a job or promotion, and last but not least, going out less frequently. Although many cannabis users might still like to smoke a joint, they cannot combine it anymore with their new lifestyle and responsibilities, or the situation in which they usually used cannabis does not occur anymore.

In our survey, 93 of the 217 respondents had quitted their cannabis use at time of the interview. We regard a respondent as having quitted cannabis when meeting one (or both) of the following conditions:

1. The respondent answered affirmatively to a question in which it was asked if the respondent considered himself to have quitted (73 persons), or
2. He or she did not report any hashish or marihuana use during the last twelve months prior to the interview (83 persons).

Of course we can not exclude the possibility that quitters start again, but in this analysis we will consider them as having quitted cannabis use. Figure 4 shows the age at which they quitted. Two respondents reported having quitted their use at the age of 14. About ten percent of the respondents reports to have quitted before the age of 19. A very large majority, 90 percent, reports to have quitted before the age of 38.

Figure 4. Age of last cannabis use in experienced cannabis users who had quitted

Table 1 shows the reasons our respondents gave for quitting. 'No need' for cannabis was the reason given by 66 percent of the respondents.

The second explanation for cannabis users to quit their use is experiencing negative effects. Thirty-nine percent of the respondents mentioned undesirable or negative effects of cannabis as the reason to quit cannabis use. Seventeen percent of the respondents mentioned predictable effects of cannabis like getting sleepy, absent-mindedness, loss of concentration, and the influence on functioning in daily life. So-called unpredictable effects of cannabis, like anxiety and panic were reported by 23 percent of the respondents who had quitted cannabis use.

Some people quit their cannabis use all together, others merely diminish their use. Cannabis users often develop sets of rules that they apply to structure their use. Structuring their use may result in quitting, in stabilising or in diminishing one's use, depending on the demands of their life-situation (which in turn of course changes over time). In our survey we asked respondents if they recognise rules they apply to the use of cannabis. Not all of them do. Table 2 shows the rules that were reported.

More than 60 percent of the 71 respondents who report rules, formulate these rules in terms of prevention of conflicts with work or study, or in terms that limit the use of cannabis to a certain part of the day. Generally, these cannabis users prefer to use cannabis in situations that are associated with relaxing, going out with friends after the work is done. Situations in which one must be clear-headed are not regarded as suitable for cannabis use. We could expect that growing older implies a more frequent occurrence of the situations in which cannabis use is not considered `within the rules'. Of the 71 respondents who report to apply rules to their use of hashish or marijuana, 64 percent says to stick to these rules strictly. Another 34 percent says to usually stick to these rules.[4]

Even if cannabis users do not explicitly report having rules they apply to their use, they all do have some ideas about places and circumstances in which cannabis use would be appropriate, or emotions or feelings that go well with cannabis use. The most important situation that is regarded suitable for cannabis use is 'being with friends'. 'Going out' and 'going to parties' are also mentioned by many respondents. Apart from situations that are part of an outgoing lifestyle, 43 percent of all respondent says that they also smoke hashish or marijuana at home. The most frequently reported emotion that goes well with cannabis use is 'joy', reported by 35 percent of the respondents who report emotions or feelings in relation to cannabis use. 'Being relaxed', reported by 23 percent, is the second most frequently reported emotion, and 'feeling good' is in third place, reported by 22 percent of the respondents who report emotions. This means that most of our respondents use cannabis as an amplifier of pleasure, and not as a depressant.

Cannabis users may not only let their use depend on certain situations or emotions. One third of the respondents indicated that they had put a limit to the amount of money they spend on hashish or marijuana.

Most cannabis users have experienced some more or less adverse effects. We presented the respondents a list of over a hundred possible (adverse) drug effects, and asked them if they ever had these experiences and if they saw these experiences as resulting from cannabis consumption.

'A cotton mouth' is the most frequently reported effect of cannabis (94%). Around 80 percent of the respondents also reports 'mind wanders' and 'lack of concentration'.

We also asked our respondents a variety of questions regarding a negative influence on their lives and the progression to other drugs. These questions were phrased in terms of possible influence, and our respondents could answer these questions with a simple 'yes' if they had ever experienced such an influence during the full length of their career.

• Half of the respondents had ever found him or herself using larger amounts of marijuana (or hashish) than he or she intended to, or used it for longer periods than he or she intended to, for more than a week.
• Thirty percent of the respondents had ever felt a persistent desire to cut down on marijuana use or tried unsuccessfully to cut down, for more than a week.
• Twenty-four percent of the respondents had ever given up or reduced social, recreational or work activities because of their marijuana use for more than a week.
• Seventeen percent had ever kept using marijuana for more than a week when they had a recurring physical or psychological problem that was either caused by or worsened by marijuana use.
• Twenty-three percent had ever failed to meet obligations at work or school or home for more than a week because of his or her marijuana use.
• Five percent of our respondents had ever had recurring legal problems because of marijuana use.
• Seventeen percent had ever kept using marijuana for more than a week when he or she was having recurring social or interpersonal problems that were caused or worsened by marijuana use.
• Twenty-three percent indicated that there were periods in which cannabis use was an obsession for them.

The reader has to keep in mind that our questions were very widely phrased: we asked if our respondents had ever experienced the mentioned effects during their use career.

Despite the reported experience with problems, at the time of the interview almost all respondents (98 percent) indicated that they were in control of their cannabis use. However, it is clear that many cannabis users (although a minority) experience negative influences of cannabis use at some point in their cannabis using career, but are able to overcome these themselves.

We also asked if the respondents ever received any treatment or counselling for a drug or alcohol problem in the last two years. Twelve persons reported having been in contact with treatment or counselling, but only one person reported that this contact was in connection with his cannabis use. The others sought help in relation to their use of alcohol or cocaine.

Other drug use

The assumption that people who use cannabis, inevitably proceed to hard-drugs (the so-called Gateway Theory or Stepping Stone Hypothesis) can be more or less tested with the data we gathered in the Amsterdam cannabis survey. Among the group of cannabis users in Amsterdam we find higher use of other illicit drugs than with persons who never used cannabis (Cohen and Sas, 1996) If we look at the life time prevalence of other drug use, we see that 65 percent in our sample of experienced cannabis users have experience with one or more other drugs.[5] Lifetime prevalence of illicit drugs among experienced cannabis users is significantly higher than in the general population of Amsterdam, but also higher than in the total group of cannabis users. In the latter group we found that 25% has lifetime experience with other drugs. However, if we look at the prevalence of other illicit drug use in the group of experienced cannabis users during the last three months prior to the interview, we see that the vast majority (over 90 percent) is not currently using these other drugs.

For each drug we found a number of respondents who report lifetime experience. This experience ranges from 4 percent of our group of respondents (smokable cocaine) to 99 percent (alcohol). Does this mean that for these experienced cannabis users hashish or marijuana acted as a stepping stone to these other drugs?

Per group of respondents who report life time experience of a certain drug we computed time of onset of this drug. For a large part of the experienced cannabis users, alcohol and tobacco came first. For all of those who report lifetime experience with smokable cocaine and with ecstasy, cannabis came first. This is valid for almost all of those who report life time experience with the other illicit drugs. Although 65 percent of the experienced cannabis users we interviewed tried at least one other drug, only a small percentage has been using these other drugs with some sort of regularity.

Our data suggest that cannabis use and getting some experience with other drug use are caused by the same phenomenon: curiosity for new experiences that fit into the lifestyle of young adults. This curiosity exists however in very different amounts for the different illicit drugs which is shown by the large differences in lifetime experience of the different drugs. For the larger part of experienced users of cannabis, other drugs play a small or non existent role. This could indicate that for most experienced cannabis users, cannabis satisfies their curiosity in a sufficient way.

Another explanation for the relatively small role of other drugs in the use patterns of these experienced cannabis users might be that cannabis is more easily available in Amsterdam than other drugs. This more easy availability channelled or contained some of the drug curiosity these experienced users may have had. However, this explanation is not very convincing because these experienced cannabis users usually know enough persons that use or have used other drugs. Restricted availability is therefor only a limited explanation for the low levels of other drug use we find among our respondents.

Table 5 shows that quitting cannabis use predicts very low last 3 months prevalence for all illicit drugs. This is less so for reaching the age of 30 and older, and for some drugs there is no effect at all (cf. very low last 3 months prevalence for opiates, amphetamine and smokable cocaine in all three groups).

Conclusions

Sustained high level marijuana use (more than 10 grams per month) is relatively rare. Only 5.5 percent reports a high level of use during the last three months prior to the interview. But, thirty-three percent of experienced cannabis users report ever having used at a high level at some point during his or her career. 43 percent reports to have quit at time of interview. Decreasing level of use over time — when cannabis users grow older — or quitting altogether applies to more than half of all respondents.

Although 45 percent of the experienced cannabis users we interviewed report having first hand knowledge of negative effects of hashish or marijuana on one or more aspects of life, this did not lead to an escalation of problems. In fact all respondents but one were able to regulate their cannabis use on their own, either by quitting or cutting down their use, or applying stricter rules to their use.

Sixty-five percent of experienced cannabis users experiment with other drugs. Frequent or current other drug use is rare. Other drug use might be repeated as long as it fits into the lifestyle of the user. With decreasing levels of cannabis use, what ever other drug use has existed disappears or almost disappears.

Notes

References

Cohen, Peter (1989), Cocaine use in Amsterdam in non deviant subcultures. Amsterdam, Department of Human Geography, University of Amsterdam.

Cohen, Peter & Arjan Sas (1993), Ten years of cocaine. A follow-up study of 64 cocaine users in Amsterdam. Amsterdam, Department of Human Geography, University of Amsterdam.

Cohen, Peter & Arjan Sas (1996), Cannabis use as a stepping stone to other drug use; The case of Amsterdam. Amsterdam, CEDRO.

CNN (1996), Higher Times.

Sandwijk, J.P., P.D.A. Cohen, S. Musterd & M.P.S. Langemeijer (1995), Licit and illicit drug use in Amsterdam II. Report of a household survey in 1994 on the prevalence of drug use among the population of 12 years and over. Amsterdam, Dept. of Human Geography, University of Amsterdam.