Abraham, Manja D.,
Hendrien L. Kaal, & Peter D.A. Cohen (2002), Licit and illicit
drug use in the Netherlands 2001. Amsterdam: CEDRO/Mets en Schilt.
© Copyright 2002 CEDRO Centrum voor Drugsonderzoek.
Licit and illicit drug use in the Netherlands 2001
Chapter 5: The prevalence of drug use: Core indicators
Manja D. Abraham, Hendrien L. Kaal, & Peter D.A. Cohen
- Table 5.1: Lifetime drug use prevalence in the Netherlands in seven samples: Amsterdam, Rotterdam, and five categories of address density municipalities, 1997 and 2001 (weighted percentages, index figures: 1997 = 100)
- Table 5.2: Last year drug use prevalence in the Netherlands in seven samples: Amsterdam, Rotterdam, and five categories of address density municipalities, 1997 and 2001 (weighted percentages, index figures: 1997 = 100)
- Table 5.3: Last month drug use prevalence in the Netherlands in seven samples: Amsterdam, Rotterdam, and five categories of address density municipalities, 1997 and 2001 (weighted percentages, index figures: 1997 = 100)
- Table 5.4: Unweighted n reported lifetime drug use in the Netherlands in seven samples: Amsterdam, Rotterdam, and five categories of address density municipalities, 1997 and 2001
- Table 5.5: Lifetime drug use prevalence in the Netherlands in seven samples: Amsterdam, Rotterdam, and five categories of address density municipalities, 1997 and 2001 (weighted population estimate and 95% confidence interval), reported in thousands
- Table 5.6: Last month drug use prevalence in the Netherlands in seven samples: Amsterdam, Rotterdam, and five categories of address density municipalities, 2001 (weighted population estimate and 95% confidence interval), reported in thousands
- Table 5.7: Lifetime and last month drug use prevalence in the Netherlands by gender, 1997 and 2001 (weighted percentages)
- Table 5.8: Last year drug use continuation in the Netherlands in seven samples: Amsterdam, Rotterdam, and five categories of address density municipalities, 1997 and 2001; as a percentage of all lifetime users (weighted percentages, (index figures: 1997 = 100)
- Table 5.9: Last month drug use continuation in the Netherlands in seven samples: Amsterdam, Rotterdam, and five categories of address density municipalities, 1997 and 2001; as a percentage of all lifetime users (weighted percentages, index figures: 1997 = 100)
- Table 5.10: Experienced drug use in the Netherlands in seven samples: Amsterdam, Rotterdam, and five categories of address density municipalities, 1997 and 2001 (weighted percentages)
- Table 5.11: Unweighted n reported last month drug use in the Netherlands in seven samples: Amsterdam, Rotterdam, and five categories of address density municipalities, 1997 and 2001
- Table 5.12: Number of use-days as a percentage of last month users in the Netherlands in seven samples: Amsterdam, Rotterdam, and five categories of address density municipalities, 1997 and 2001 (weighted percentages)
- Table 5.13: Incidence of drug use in the Netherlands in seven samples: Amsterdam, Rotterdam, and five categories of address density municipalities, 1997 and 2001 (weighted percentages)
- Table 5.14: Mean age of first drug use in the Netherlands in seven samples: Amsterdam, Rotterdam, and five categories of address density municipalities, 1997 and 2001 (weighted)
- Table 5.15: Mean age of current drug users (reported last month) in the Netherlands in seven samples: Amsterdam, Rotterdam, and five categories of address density municipalities, 1997 and 2001 (weighted)
This chapter presents an overview of drug use in the population of 12 years and over in the Netherlands in 2001. Nationwide estimates are given, as well as estimates for Amsterdam and Rotterdam, and for each of five address density strata. Where possible, comparisons are made with the estimates for drugs use in 1997.
Paragraph 5.2 addresses the question how many people use or have used a certain drug ever in their lives, in the last year, or in the last month. As prevalence rates alone are not sufficient to describe drug use in society, they are complemented with other indicators. The indicators used are continuation and incidence of drug use (paragraph 5.3), frequency and intensity of drug use (paragraph 5.4), and mean age of first and current use (paragraph 5.5). These core indicators are given for the following drugs: tobacco, alcohol, hypnotics, sedatives, cannabis, cocaine, amphetamine, ecstasy, hallucinogens, LSD, mushrooms, all opiates, morphine, codeine, heroin, inhalants, smartdrugs, herbal ecstasy, guarana and the like, performance enhancing drugs, and a category created for this survey: difficult drugs.
The concept of 'difficult drugs' was introduced in 1990 to avoid definition problems (Sandwijk et al. 1991). It was decided not to use the term 'hard drug' because of its many non-scientific connotations. Also, the term 'hard drug' might give the impression that one is referring to a particularly hazardous category of drugs and that 'soft drugs' on the contrary pose (almost) no health risk. A seemingly simple division into licit and illicit drugs could not straightforwardly be made, due to the specific wording of the Dutch Opium Act. This Act makes a distinction between cannabis and other illicit drugs, such as cocaine, amphetamine, ecstasy, hallucinogens, LSD and heroin. Both categories of drugs are illicit, but priority for criminal investigation and prosecution is given to the latter. So, although illegal, the possession of cannabis is not prosecuted when small amounts are concerned, making the acquisition of these drugs relatively easy. The position of mushrooms is ambiguous under Dutch law, but in practice the situation is similar to that of cannabis. The mushroom itself is legal, but the active substances psylocybin and psilocin are registered as illicit drugs. Mushroom sales, either dried or fresh, are tolerated under the current Dutch policy and occur in shops. Their purchase is not 'difficult' as that of other drugs, and in this study, mushrooms therefore fall under the category hallucinogens, but not under 'difficult drugs'. Thus defined, the category 'difficult drugs' consists of amphetamine, cocaine, ecstasy, all hallucinogens apart from mushrooms, and heroin.
In 2001, smartdrugs were added to the list of substances asked about. Smartdrugs are a class of synthetic and natural supplements taken to enhance cognitive function. They were originally used as a treatment for memory disorders and dementia, but are now increasingly used by healthy people to increase alertness, energy, short and long term memory capacity, concentration levels, and work performance. Examples of substances falling under this category are ephedra, herbal ecstasy, guarana, and fast blast. Smartdrugs are legally available and are amongst others sold in so-called 'smartshops'. Therefore, they do not fall under the category 'difficult drugs'. As no questions on smartdrugs were included in the 1997 survey, no analysis can be made of their growth in popularity.
The 1997 report did not include separate figures on LSD and morphine. Because of the relatively large percentage of people ever having used these substances, it was decided to report separately on these drugs this time. Even though they were not reported, the 1997 survey did include questions on morphine, and these data are used for comparison in the tables printed here. Only lifetime prevalence of LSD was asked about in 1997, not last year or last month, so for this drug no full comparisons can be made. For the generic drug categories such as opiates, or hallucinogens, no data are available on intensity and frequency of use in 2001: these questions were asked for each of the drugs falling into these categories, but it was felt they could not be combined.
The tables in the 1997 report list doping, where in this report uses the term 'performance enhancing drugs' is used. The latter term is preferred since the term doping includes a much wider range of substances and practices. Cannabis, for example, features on the IOC doping list, but also blood transfusions fall under the term doping (IOC 2001). The term 'performance enhancing drugs' emphasises that it is the purpose with which these substances are consumed that is important here. Although the term used in this report is different, the substances asked about are the same as in 1997. The generic category 'performance enhancing drugs' in this study includes anabolic androgen steroids (AAS), growth hormone, erythropoietin (EPO), thyroid gland preparation, clenbuterol, and stimulants (e.g. amphetamine, cocaine, and caffeine) taken in high doses to enhance performance.
5.2 Prevalence and continuation of drug use
The tables for this section show lifetime prevalence rates (table 5.1), last 12 months prevalence rates (table 5.2), and last 30 days prevalence rates (table 5.3) of licit and illicit drug use for the population of the Netherlands aged 12 years and over in 2001. For each of these tables an index was created, giving a proportionate figure for the 2001 prevalence rates if the rate in 1997 was set on 100. This aids us looking for trends in use between 1997 and 2001. Table 5.4 gives the unweighted number of observed lifetime users.
For lifetime use and last month use population estimates are included (table 5.5 and 5.6), showing how many people in the Netherlands aged 12 years and over are estimated to have ever used a drug or to have used it in the last month. These figures are given in thousands. They are followed by 95 per cent confidence intervals, which means that on the basis of this study one can be 95 per cent confident that the true number of users of a drug falls within the brackets given.
Table 5.7 displays the lifetime and last month prevalence rates for men and women on a national level. Tables 5.8 and 5.9 show the last year and last month continuation rates of drug use. Last year continuation shows what proportion of lifetime users reports last year use as well; last month continuation shows what proportion of lifetime users also reports last month use. These figures give an indication of how many people who have experience with a drug, continue to use this drug beyond experimentation. Here again, index figures were produced with the 1997 rates being 100. Also for future reports, the 1997 values will be maintained as the basis for index-figures.
Tobacco and alcohol
Tobacco and alcohol are the most commonly used drugs. Alcohol is top of the list, with 91.6 per cent of the population of 12 years and over ever having used it, followed by tobacco with 66.4 per cent.
There is only a slight variation in the lifetime prevalence of tobacco between the cities and address density strata. In 1997, lifetime prevalence was relatively high in Amsterdam, but the use of tobacco there was decreased towards the national average. Overall, the extent of tobacco use has decreased since 1997 - this decrease is strongest for the youngest age group (12-15 year-olds), especially in the lower and lowest address density strata. The last year and last month continuation rates have gone down - from 56.1 to 52.1 per cent and from 50.5 to 45.6 per cent respectively - which shows that relatively more people have given up smoking recently. However, continuation rates are still high and they are higher in the cities and the higher address density strata than in the lower address density areas, most so in Amsterdam.
The use of alcohol has slightly increased since 1997: lifetime prevalence increased from 90.2 to 91.6 per cent, last year prevalence from 82.5 to 83.8 per cent and last month prevalence from 73.3 to 75.1 per cent. This increase was mostly found in the lower address density areas. Continuation rates increased slightly as well. For lifetime prevalence the trend seen in Amsterdam was the opposite, with a slight decrease from 88.7 to 87.2 per cent. In general, the prevalence figures for alcohol in Amsterdam and Rotterdam were lower than in the rest of the Netherlands. The youngest age group (12-15 years) showed an exception to the general trend as well: here there was a slight decrease in lifetime prevalence in almost all strata, even though the last month figures showed an increase.
Hypnotics and sedatives
Hypnotics and sedatives are legally obtainable. Just under one fifth of the population of 12 years and over has ever used these substances. Hypnotics use amongst the highest age category (70 years and over) is even higher: almost one third of respondents reported they had ever used hypnotics, while almost one fifth said they had done so in the last month. Hypnotics and sedatives are seldom used amongst the youngest age groups, although the use of hypnotics amongst 12-15 year-olds increased since 1997. Unlike most substances, both hyponotics and sedatives were used more by women than by men. Whereas overall the use of hypnotics increased since 1997, the use of sedatives showed a slight decrease. Exceptions are found in Amsterdam, where contrary to the general trend the use of hypnotics in the last year and the last month decreased slightly, and in the lowest address density areas, where a slight increase in the use of sedatives was found. In 1997, use rates of hypnotics and sedatives in Amsterdam were much higher than anywhere else, and although they are still higher, the difference is not nearly as large now. Continuation rates of both hypnotics and sedatives are high (last year 51.8 and 46.9 per cent respectively), and both last year and last month continuation figures for both drugs showed an increase.
Since 1997, the use of cannabis increased almost everywhere in the Netherlands. In 2001, 17 per cent of the respondents reported they had ever used cannabis (15.6 per cent in 1997), 5 per cent did so for the last year (4.5 per cent in 1997), and 3 per cent reported use in the last month (2.5 per cent in 1997). However, this increase was not seen everywhere: in Amsterdam, where cannabis use is found to be much higher than anywhere else, last year and last month prevalence decreased slightly since 1997, as did last year use in the low and lowest address density areas. However, cannabis use is still much more widespread in Amsterdam than anywhere else. Use figures are highest for the 20-24 years age group; the increase of use is also strongest for this group. At the same time, there was a decrease in lifetime prevalence (but not in last month prevalence) amongst the 12 to 15-year-olds.
Overall, last year continuation rates of cannabis use are fairly stable, at 29.3 per cent; there was a strong increase in the high address density areas, a moderate increase in Rotterdam, and a slight decrease in the other areas. Last month continuation rates increased slightly from 15.8 to 17.7 per cent. This trend was seen everywhere but in Amsterdam and the low address density areas.
The use of difficult drugs (amphetamine, cocaine, ecstasy, all hallucinogens apart from mushrooms, and heroin) increased slightly since 1997 in all strata. Lifetime prevalence of difficult drugs increased from 4.1 to 4.9 per cent. Last year prevalence in 2001 was 1.8 per cent, while 0.8 per cent reported difficult drug use in the month before being interviewed. The prevalence of difficult drug use increases with address density, and Amsterdam has more users of difficult drugs than anywhere else in the Netherlands. The use of difficult drugs already was highest amongst the 20 to 24-year-olds, and has since 1997 almost doubled in this age group, both for lifetime and last year use. Both last year and last month continuation rates of difficult drugs increased, from 29.4 to 35.9 per cent and from 12.2 to 16.5 per cent respectively. Only for Amsterdam there was a slight decrease in last year continuation. It is important to realise that continuation rate now refers to the use of any difficult drug, so continuing difficult drug use does not have to mean that the user stuck to the same type of drugs.
Cocaine, amphetamine and ecstasy
The use of cocaine, amphetamine and ecstasy has increased everywhere between 1997 and 2001. Lifetime prevalence was equal for cocaine and ecstasy at 2.9 per cent, while the lifetime prevalence for amphetamine was only slightly lower. In the last year and the last month ecstasy was the most used drug of the three, with a prevalence rate of 1.2 and 0.5 per cent respectively, followed by cocaine (0.9 and 0.4 per cent) and then amphetamine (0.5 and 0.2 per cent). Use of these drugs is more prevalent in the cities and the higher address densities, and although the increase in Amsterdam was slightly less than elsewhere, use rates in Amsterdam continue to be the highest. As was true for difficult drugs in general, the use of these three drugs is highest in the age group 20-24 year-olds. Last year and last month continuation rates increased for all three drugs, but most strongly for ecstasy. The last year continuation rate for ecstasy is now 41.5 per cent, much higher than for cannabis (29.3 per cent), and almost as high as for sedatives (46.9 per cent). However, the last month continuation rate of ecstasy is very similar to that of cannabis and much lower than that of sedatives. The continuation rates for amphetamine are still much lower than those for ecstasy or cocaine, 18.5 per cent for the last year and 8.5 per cent for the last month, showing that amphetamine might used for briefer episodes or less infrequently.
Lifetime prevalence of hallucinogens excluding mushrooms is no more than 1.3 per cent, while 1.0 per cent reported LSD use in particular. Lifetime and last year prevalence of hallucinogens decreased in all strata except Rotterdam. Especially in Amsterdam the lifetime prevalence rate decreased strongly, but although the difference has become smaller, hallucinogens are still much more used in the capital than anywhere else in the Netherlands. Last month prevalence is very low and also decreased in the Netherlands as a whole. Last year and last month continuation rates for hallucinogens are very low compared to those for other drugs and decreased strongly: they almost halved. This suggests that hallucinogens use is generally very sporadic and has become less fashionable.
Although the lifetime prevalence of mushrooms increased from 1.6 to 2.6 per cent nationally, both last year and last month prevalence decreased with about 15 per cent to 0.5 and 0.1 per cent respectively. The decrease in continuation rates also suggests that mushrooms are used slightly less often now than in 1997. Continuation rates for mushrooms are higher than those for other hallucinogens: the last year continuation rate of 19.8 per cent is comparable with the rate for amphetamine; the last month continuation rate of 3.5 per cent however is much lower, which shows that mushrooms are not used very frequently.
The reported use of opiates decreased strongly; this seems to be explained by a strong decrease of codeine and morphine use. In an earlier report (Abraham et al. 1998) it was found that the rate of codeine use in 1997 in Amsterdam was much higher than previous studies in this city had shown. This was explained by referring to a possible increase in the prescription of codeine containing preparations. On the basis of the findings for 2001 it seems more likely that the figures for medicinal opiates for 1997 are simply unreliable. Why this is the case, however, is not clear. The figures for codeine use in 2001 are still twice as high as in 1994.
Heroin is only used by a very small percentage of the population. Only 0.4 per cent of the population of 12 years and over has ever used heroin, an increase compared to 1997 when 0.3 per cent had ever used heroin. Lifetime prevalence in the highest address density areas is much higher than in the rest of the country (0.9 per cent), and in Amsterdam the use is higher: still 1.3 per cent of the capital's population has ever used heroin. However, compared to 1997 the use of heroin in Amsterdam has decreased with around a quarter. Last year and and last month use of heroin in Amsterdam have even decreased to a third of the 1997 levels. The last year continuation rate of heroin is amongst the lower rates, and has remained stable around 22 per cent; the last month continuation rate has increased from 10.2 to 15.1 per cent, and is comparable with the last month continuation rate of cannabis, cocaine and ecstasy.
Inhalants have increased in popularity, although they are only used by a small proportion of the population: 0.8 per cent of the population of 12 years and over report to have used inhalants ever in their life, 0.2 per cent did so in the last year and 0.1 per cent in the last month. The continuation rates of inhalants have also increased, the last month continuation even having more than doubled to 15.7 per cent, which is in the region of the continuation rates of cannabis, ecstasy and heroin.
Smartdrugs were added to the survey for the first time in 2001, so no comparison with earlier figures can be made. The proportion of the population that has ever used smartdrugs (2.5 per cent) is only slightly lower than the proportion of the population who have used cocaine, amphetamine, ecstasy or mushrooms. Last year prevalence is 0.9 per cent, last month prevalence 0.3 per cent. The use of smartdrugs is much more prevalent in the highest address density areas than anywhere else. Especially Amsterdam has many smart drug users; use in Rotterdam is relatively low considering the address density. Smartdrugs are mainly used by the 20-24 year-olds, apart from Rotterdam, where the user group is slightly older. Continuation rates are average, only the last month continuation rate of herbal ecstasy is relatively low: 4.1 per cent. This suggests that herbal ecstasy is used more sporadically than other smartdrugs.
Only a small proportion of the population uses performance-enhancing drugs. Lifetime prevalence was 0.7 per cent, last month prevalence 0.2 per cent. The use rates are fairly evenly spread over the address density areas. Continuation rates for these substances are relatively high, comparable to that of ecstasy and sedatives, and seem to have increased.
'No drugs' is defined as no use of any of the listed drugs. Thus, 'no drugs' means that alcohol, tobacco, sedatives, hypnotics, codeine, performance-enhancing drugs or smartdrugs were not used either. As smartdrugs were not asked about in the 1997 survey, figures of the two surveys are theoretically not strictly comparable. However, as there were no people in 2001 that used smartdrugs but no other drugs, this is not a problem in practice. In 2001, 5.3 per cent of the population had never used any drugs, almost the same percentage as in 1997. The proportion of the population who had not used any drugs in the past year has gone up albeit only very slightly (from 10.6 to 11.1 per cent) as has the proportion of last month abstainers (17.8 to 18.2 per cent). The proportion of non-drug users is higher in the highest address density areas, especially in Amsterdam and Rotterdam. So, both the use of drugs, and the non use of drugs are occurring most in the highest address density areas, suggesting that the newest fashions around drugs (like complete abstinence) are showing there first, and most. It goes without saying that continuation, frequency, intensity and age of onset of this category cannot be calculated.
5.3 Frequency and intensity of drug use
In this paragraph two indicators of the intensity of drug use are presented. The first is the concept of 'the experienced user'. An experienced user is defined as a person who used a specific drug 25 times of more during his or her life. The rate of experienced users is the proportion of the total user population that used a drug 25 times or more. These rates are shown in table 5.10. It is important to keep in mind that these rates refer to lifetime users of a substance and not to the entire Dutch population. As a consequence, for some drugs the total number of lifetime users is too small (<50) to provide accurate estimates of the experienced user rate reported. Where this is the case, no estimates are given in the table.
Another indicator of the intensity of drug use that has been used here is the number of drug use days in a month. This question was only asked to last month users relating to the last month of use. This measure of the intensity of use has been expressed as a proportion of all last month users that used on more than 20 days during the last month. The sample of last month users was too small (<50) for almost all drugs to give accurate estimates for anything but the national situation (see table 5.11). Table 5.12 shows the estimates that could be given. Only for alcohol, hypnotics, sedatives and cannabis was it interesting to make a more detailed analysis of the intensity of use: for these drugs a table was created in which less frequent use was also included (table 5.12). For tobacco, the question about number of 'use days' was not included.
Tobacco and Alcohol
The highest rates of experienced drug use are for alcohol and tobacco. No fewer than 86.1 per cent of all tobacco users of 12 years and over used more than 25 times, while 85.6 per cent of all alcohol users used more than 25 times. These figures are slightly lower than in 1997. This decrease was seen in all strata, but was strongest in the lower address density areas and, to a lesser extent, Rotterdam.
The number of alcohol use days of past month users decreased slightly compared to 1997 in all areas except in Amsterdam, where the average number of use days seems to have gone up. However, this increase has taken place in the lower intensities of use, as the proportion of users who used more than 20 days has remained stable. Nationwide, around one-third of last month alcohol users only used alcohol 1-4 days in the last month, while just over a fifth of the current users drinks more than 20 days a month. In Amsterdam the intensity of alcohol use is slightly higher.
Hypnotics and sedatives
The rate of experienced use of hypnotics and sedatives is much lower than that of alcohol and tobacco, but these drugs are nevertheless used more than 25 times by no fewer than 42.6 and 46.8 per cent respectively of the total user population. Especially the rate of experienced sedatives users has gone up considerably (in 1997 39.6 per cent of lifetime users were experienced users). Only in Amsterdam the trend was opposite: there, the proportion of experienced sedative users decreased from 45.7 per cent in 1997 to 38.8 per cent in 2001. Other than this exception, experienced use amongst lifetime users seems fairly evenly spread amongst the address density areas.
Sedatives are used more intensively than hypnotics: 34.5 per cent of last month hypnotics users reported more than 20 use days, compared to 46.7 per cent of last month sedatives users. For hypnotics, there was a strong decrease in the proportion of current users who reported more than 20 use days in the last month in most areas; in Rotterdam and the moderate and lowest address density areas the level of experienced use was more or less stable. For sedatives a strong decrease was seen in most areas, but because an increase in the level of experienced use was seen in the low and lowest address density areas, the national figures only seem to have changed slightly. Whereas there does not seem to be a real pattern in the intensity of hypnotics use in the different strata, there is a clear trend that the lower the address density, the higher the intensity of last month use of sedatives. Thus, whereas in Amsterdam the intensity of hypnotics and sedatives use is almost equal (31.6 and 31.3 per cent of users reported more than 20 use days), in the lowest address density area the difference is considerable (37.7 per cent for hypnotics compared to 60.4 per cent for sedatives).
The level of experienced use of cannabis is stable in all strata. Around one third of cannabis users in the Netherlands can be labelled an experienced user. However, this proportion is higher in the highest address density areas and lower in the lowest. In Amsterdam 43.6 per cent of lifetime cannabis users reported more than 25 times use, which was very similar to the findings for this city in earlier years.
The intensity of last month use in Amsterdam is also slightly higher than elsewhere, but even there more than 40 per cent of current users reported to use cannabis once a week or less. Never the less, only a quarter of all current cannabis users in Amsterdam reported to use more than 20 days a month. Nationally, the number of cannabis use days seems to have decreased somewhat. However, in the highest address density areas (including Amsterdam and Rotterdam) there has been a slight increase in the average number of use days. For the two lowest address density areas no estimates of intensity of use could be given, as there were too few last month users in the samples.
Cocaine, amphetamine, and ecstasy
The level of experienced use of cocaine, amphetamine and ecstasy is of the same order: in 2001, 29.3 per cent of cocaine users were experienced users, compared to 33.7 per cent of amphetamine users and 29.8 per cent of ecstasy users. In 1997, the experienced use rates in the Netherlands for cocaine and ecstasy were considerably lower. In Amsterdam, the rate of experienced users of cocaine and especially amphetamine decreased since 1997, and is now lower than the national rate. At the same time, the rate of experienced ecstasy users in the capital was very low in 1997, and increased towards the national rate in 2001. In the other highest address density areas the rate of experienced users increased for all three drugs. For the lower address density no estimates could be made due to the small numbers of users in these samples.
Cocaine, amphetamine and ecstasy are used frequently by only a small proportion of the current users: nationally 4.5 per cent of current cocaine users and 0.6 per cent of current ecstasy users reported more than 20 use days over the last month. Due to small numbers of current users in the samples, no estimates of the level of experienced use are available for amphetamine or for any of the separate strata. Although the number of drugs use days is still low, it does seem to have gone up: in 1997 only 1.8 per cent of current cocaine users and none of the current ecstasy users reported more than 20 use days. However, due to the small number of current users this seeming increase might also be the result of chance.
In 2001, no questions were asked on the number of drug use occurrences of hallucinogens users. However, data are available for subgroups of the hallucinogens users, amongst which for the LSD users, the largest group of hallucinogens users. This shows that the proportion of lifetime LSD users that is experienced is not very high: only 15.6 per cent of users report to have used more than 25 times. Due to the small number of last month users, no estimates can be given of the intensity of current LSD use.
The proportion of experienced users of mushrooms has gone up slightly since 1997, from 4.7 to 6.7 per cent. However, compared to other drugs, this percentage is still very low. Only for Rotterdam is the percentage of experienced users considerably higher (15.3 per cent), but this is still a lot lower than for almost any of the other drugs for which data are available. Again, due to the small number of last month users, no estimates can be given of the intensity of current mushroom use.
The rates of experienced use of morphine (9.2 per cent) and codeine (28.4 per cent) have gone up, but the problems with comparability of the 1997 figures for these substances were already discussed in the previous paragraph. The rates are not equally spread over the strata, but no real pattern can be seen when looking at address density and experienced use rates. Only for codeine can a national estimate be made of the intensity of use: 10.7 per cent of last month users reported to have used more than 20 times in the last month. In 1997 this rate was 13.6 per cent.
The experienced use rate for heroin has gone up considerably since 1997: 38.6 per cent of users now, compared to 24.3 per cent of users in 1997, reported to have used heroin more than 25 times. No estimates can be given for the separate strata, but the experienced use rate in the combined highest address density areas is higher (45.2 per cent) than the national rate. No estimates can be given of the intensity of current heroin use due to the small number of last month users.
The experienced use rate for inhalants has increased from 16.0 per cent in 1997 to 19.7 per cent in 2001. However, this rate is still at the lower end of the spectrum. For performance enhancing drugs the experienced use rate has increased from 30.7 per cent to 44.3 per cent, a level comparable to that for hypnotics and sedatives. The experienced use level in the combined highest address density areas was higher still: no fewer than 62 per cent of all users here reported to have used performance enhancing drugs more than 25 times. No data were available for the overall category smartdrugs, and no estimates for intensity of use of any of these substances could be given due to small numbers.
5.4 Incidence of drug use
The concept discussed in this paragraph is that of 'incidence'. The term 'incidence' of drug use refers to the proportion of the entire research population that started using a particular drug within the year prior to the interview. Incidence rates should give us some insight in the spread of drugs amongst the population: an increase in incidence rate suggests that in time an increase in lifetime prevalence should be expected, whereas a decrease in incidence rate correspondingly predicts a decrease in prevalence. The incidence figures are based on the age of the respondents and the reported age of first use. Table 5.13 shows the estimates of drug use incidence for all strata.
Tobacco and alcohol
The national incidence rate of tobacco was 1.3 per cent, which means that an estimated 1.3 per cent of the Dutch population of 12 years and over started smoking in the year before interview. This incidence rate is fairly similar in all address density areas. The incidence rate of alcohol was 2.9 per cent, and for this substance it was found that the lower the address density, the higher the incidence rate. The incidence rate of tobacco has decreased a little since 1997, for alcohol the incidence rate is fairly stable.
Hypnotics and sedatives
The incidence rates for hypnotics and sedatives have both decreased. In 1997, the incidence rates for both substances were 2.9 per cent. This time, the incidence rate for hypnotics had dropped to 2.5 per cent, while the incidence rate for sedatives had even dropped to 1.8 per cent. In 1997, the incidence rate of both hypnotics and sedatives was much higher in Amsterdam than anywhere else in the country. Although they are still higher than the national rates now, the difference is much smaller. For hypnotics no relationship between incidence and address density could be found, for sedatives it seems to be the case that the higher the address density, the higher the incidence rate.
The incidence rate of cannabis has decreased from 1.3 per cent in 1997 to 1.0 per cent in 2001. The decrease seems to have been slightly stronger in the lower address density areas. Whereas in 1997 it was found that there were no significant differences between the incidence rates of the various strata - which suggested that the lower address density areas might have been 'catching up' with the more densely populated areas with regard to cannabis prevalence - now the lower address density areas seem to have lower incidence rates for cannabis. This matches the current prevalence figures, and suggests there is no reason to expect a change in the differences in cannabis prevalence between the strata.
The incidence rates decreased or remained stable for all other substances mentioned in this study, except for ecstasy. This is interesting as it suggests that the growth of the drug using population decreases or at least stabilises. For ecstasy, a small increase in incidence rate could be seen in all areas apart from Amsterdam. However, despite a decrease in Amsterdam, the incidence rate for ecstasy is still higher in this city than in the rest of the country. Furthermore, in the moderate to lowest address density areas the incidence rate of cocaine increased, and is now more similar to the national average. Overall, the incidence rates for all these substances are low, the highest being for the category 'opiates' (0.9 per cent), which includes the medicines morphine and codeine. The lowest incidence rates found are those for hallucinogens, heroin, inhalants and performance enhancers.
5.5 Age and drug use
Table 5.14 shows the mean age of first use of reported lifetime users. Table 5.15 presents the mean age of current users, current users being defined as those who indicated to have used a drug in the past month. As the number of last month users was not always large enough, for a number of drugs no reliable estimates could be given. The difference in time between the age at first use and the age at current use can be used as an indication of the relative length of user careers, although it is clearly no measure of the length of user careers. This difference varies largely between drugs: judging by this variable ecstasy careers are much shorter than for example cocaine careers. However, it should be borne in mind that ecstasy is a more 'recent' drug, and that many careers will therefore potentially get longer.
Tobacco and alcohol
The average age of first use of alcohol and tobacco is lower than for any of the other drugs. On average, the users started smoking tobacco when they were 16.8 years old, while they started drinking alcohol at 17.5 years old. This is slightly younger than what was found in 1997. At the same time, the average age of current alcohol and tobacco users is high (43.3 and 40.6 years respectively), comparable to that of current codeine users and only lower than the average age of current hypnotics and sedatives users.
Hypnotics, sedatives and pharmaceutical opiates
The age of first use of hypnotics and sedatives (38.8 and 34.1 years respectively) is comparable to that of morphine and codeine (32.6 and 31.0 years respectively), and considerably higher than that of non-pharmaceutical drugs. There has been a slight decrease in age of first use for all pharmaceutical drugs compared to 1997. Hypnotics and sedatives user careers seem to be long; the average age of the current hypnotics user is no less than 58.2 years, that of the current sedatives user slightly lower at 50.9 years. The average age of current codeine users is 44.3, not far of the average age of the total sample of the population of 12 years and over. For all those drugs the mean age of current users has gone down slightly as well.
Since 1997 the average age of onset of cannabis use has remained identical: on average cannabis users were 19.7 years old when they started using. Compared to other drugs this is quite young: only alcohol, tobacco, and inhalants are usually started at a younger age. The differences between the ages of first use of the various illicit drugs are not large. The age of onset for most drugs has decreased a little. Exceptions, other than for cannabis as was just mentioned, are hallucinogens, heroin, and performance enhancing drugs. For these drugs there was a slight increase in the average age of first use. However, the differences are very small. Overall, the age of onset of difficult drugs has decreased only from 22.2 to 21.9 years, hardly a change at all.
The age at current cannabis use has not changed either: the average user is 27.9 years old, compared to 27.8 years in 1997. Only for three other drugs can reliable estimates of the average age of current users be made: for cocaine, ecstasy, and smartdrugs. The age of first use of these drugs are comparable to that of cannabis. The ages of all current users of difficult drugs is 28.8 years. This as well has changed little since 1997: in that year the average age of difficult drug users was 28.6.