CHAPTER 3: PREVALENCE AND TRENDS OF DRUG USE IN SCOTLAND
The main objectives of this chapter are to:
- outline the prevalence of drug use in Scotland among drivers aged 17-39 years
- compare these figures with previous surveys and identify any trends in drug use
- look at any changes in drug use among drivers across the past five years
- look at patterns of drug use, e.g. types of drug used, frequency of use
39% of drivers had ever used drugs, 9% had done so in the last 12 months
Reported drug use was lower than in other surveys, which may suggest that there was significant under-reporting of drug use in this survey.
Analysis was undertaken of certain demographic variables:
- more men reported drug use than women
- there was no clear age trend with more 20-24 year olds and 30-34 year olds reporting drug use compared with the other age groups
- more people who were single reported recent drug use than those who lived with a partner
The most commonly used drug was cannabis and this use was fairly frequent.
In collecting information about drug misuse, surveys tend to use the same basic approach. Respondents are presented with a list of drugs and asked if they have ever used any of those listed. Of those that have been used, respondents are asked if they have used each in the previous 12 months. In this survey, respondents were asked about 19 named drugs, one bogus substance - Semeron - used as an indicator of 'over-claiming' and three general categories of drug: other tranquilisers, pills (unknown) and something to smoke (unknown). The full list was:
- Amyl nitrate
- Magic mushrooms
- Other tranquilisers
- Pills (unknown)
- Something to smoke (unknown)
As shown in Figure 3.1, 39% of the sample reported ever having taken any of the drugs. This was higher than the figures reported in the 2000 survey (33%), and among adults in the same age group in the 2003 Scottish Crime Survey (34%).
However, just under one in ten (9%) said they had taken drugs in the last year, a lower percentage than in 2000 and 2003 where 15% said they had taken drugs in the previous 12 months.
Figure 3.1: Trends in drug use: ever and in the previous 12 months
Base: Drivers 17-39 years (1,008), Respondents 17-39 years (1,593), Drivers 17-39 years (1,031)
Previously, gender has been found to be related to drug use, with more men reporting use of drugs than women. In this survey, almost half of all men said they had ever taken drugs (45%) compared with a third of women (33%) (shown in Figure 3.2). This is consistent with the 2003 Scottish Crime Survey ( SCS), which found that 43% of men aged 17-39 years and 31% of women had ever used any of the listed drugs.
Similarly, a higher proportion of men than women had taken drugs in the past 12 months (12% of men compared with 7% of women). In comparison with the 2003 SCS, these proportions both appear to suffer from under-reporting. In 2003, 20% of 17-39 year old men and 11% of 17-39 year old women reported having used drugs in the previous 12 months.
Figure 3.2: Differences in drug use between men and women
Base: Drivers 17-39 years (1,031), Male drivers 17-39 years (502), Female drivers 17-39 years (529)
The other variable that has been consistently found to be a key predictor of drug use is age. For example, in the 2000 drugs and driving survey, drug use in the last 12 months was found to be less common among older people and most common in the 20-24 year old age group (31%).
Figure 3.3 shows the results from 2005. Unlike 2000, recent drug use was found to be least common among 17-19 year olds with 4% reporting use in the past twelve months. Recent drug use was most common in the 20-24 and 30-34 year old age groups. An important caveat, however, is that the sample sizes for both the 2000 and 2005 studies are not designed to provide estimates of change between the two surveys for the different age groups. The base size for the 17-19 year old age groups is particularly low so this should not be taken as an indication that there has been a significant reduction in drug use in 17-19 year olds.
Figure 3.3 Variation in drugs use by age
Base: Drivers (1,031), 17-19 year old drivers (62), 20-24 year old drivers (177), 25-29 year old drivers (209), 30-34 year old drivers (271), 35-39 year old drivers (312)
Again, the reported drug use appears to be low among younger respondents than would have been expected in comparison with the 2003 Scottish Crime Survey, although again, we need to be clear that the intention is to show the difference between consistent patterns in 'ever' drug use between the two surveys and divergent patterns of drug use in the past 12 months. Even though the drugs and driving survey is not designed to produce age-based estimates, we would have expected more similarity between the two surveys than these charts show,
Figure 3.4 Differences in reported drug use - 2003 Scottish Crime Survey and 2005 Drugs and Driving survey
Another key characteristic that may be related to drug use is marital or living status. It is possible that when people "settle down" with a partner and take on increased responsibilities, they become less likely to use drugs. In support of this, Figure 3.5 shows that there is little difference in drug use ever between those who live with a partner (38% reported having ever used drugs) and those who live on their own (41%). However, more than one in ten (13%) respondents who live on their own reported drug use in the past twelve months compared with 7% of respondents with a partner.
Figure 3.5 Variation in drug use by marital/living status
Base: All drivers 17-39 years (1,031), On own (484), With partner (547)
Understanding changes in measured drug use
For a number of reasons, household surveys have the potential to under-record illicit behaviours like drug use. First, it is possible that frequent drug users are less likely to be at home when interviewers call and, therefore, less likely to participate in the research. They might also be less willing to participate in research even if they are available. Secondly, there might be some stigma attached to drug use and, despite assurances of confidentiality, those who use drugs may not report use or choose to under-report it.
Overall, the analysis of patterns and trends in drug use suggests that the 2005 survey may under-state the proportion of drivers aged 17-39 years who had used drugs in the previous 12 months and there appears to be a particular problem of under-reporting among the two youngest groups of drivers - 17-19 year olds and 20-24 year olds.
The pattern of 'ever' drug use is what would be expected. Since 2000, the surveys show a steady increase in the proportion of 17-39 drivers (or 17-39 year olds) reporting that they had ever used any drugs. The proportion rises from 33% of 17-39 year old drivers in 2000 to 39% in 2005. However, the trend in '12 month' drug use shows an unexpected drop in 2005. Whereas the 2000 drugs and driving survey and the 2003 Scottish Crime Survey record that 15% of 17-39 year old drivers had used any drugs in the previous 12 months, the 2005 drugs and driving survey shows only 9%. The drop is dramatic in the 17-19 age group - 4% in this survey compared with 27% in the SCS - and in the 20-24 year old age group, which shows a drop from 28% in 2003 to 12% in 2005.
There is some evidence of declining drug use among young people. For example, in the British Crime Survey the proportion of 16-24 year old adults reporting having used any drug in the previous 12 months fell from 27% in 2000 to 23.5% in 2004/2005. 6 The decline in this survey is much greater. It seems unlikely that these changes reflect a real underlying change in patterns of drug use among young adults in Scotland. Nor do they reflect significant differences in survey method: the BCS, the SCS and the Drugs and Driving surveys used random sampling methods with self-completion data collection.
This leaves us with two possibilities:
- That patterns of drug use among 17-39 year old drivers, as measured by this survey, is different from that of the general population of 17-39 year olds as measured by the Scottish Crime Survey. Young drivers may have experimented but are substantially less likely than their non-driving counterparts to be recent or regular users. This would give similar 'ever' measures but divergent measures of drug use in the past 12 months.
- In the context of a survey on driving, young people are willing to report ever having used drugs but are reluctant to report recent drug use.
The distinction between young drivers and young people in general could arise from the fact that only a small proportion of young people are drivers. In the 2003/2004 Scottish Household Survey, only 26% of 17-19 year olds and 52% of 20-24 year olds held a full licence. This rises steadily to 80% of 35-39 year olds. The drugs and driving survey, therefore, is recording drug use among a relatively small sub-group of young people and drug use in this sub-group might be significantly different.
However, there is also evidence of under-reporting. The 2000 drugs and driving survey recorded 29% of 17-19 year olds having ever used any drugs and 20% having used drugs in the previous 12 months. The 2005 survey recorded 28% ever and only 4% in the previous 12 months in this age group. Similarly, 47% of 20-24 year olds reported ever having used any drugs and 31% in the previous 12 months. The 2005 survey recorded 41% ever but only 12% in the previous 12 months. Since both drugs and driving surveys drew their samples from 17-39 year old drivers, differences in survey coverage is unlikely to explain the differences in measures of drug use. These differences might arise either from:
- a significant but real change in behaviour, or
- a significant change in young people's willingness to report recent drug use.
Such a significant behavioural change seems unlikely so it is concluded that there has been some change in the willingness of respondents aged under 25 years to report recent drug use.
The small number of people in each of the sub-samples being compared also needs to be taken into account. The 2005 survey has 62 respondents aged 17-19 years and the 2000 survey had 60. There is significant scope for random variation in the samples to produce large differences in the estimates.
Understanding the extent to which drug use has been reported is obviously important for our understanding of the prevalence of drug use and driving. Having concluded that there appears to be under-reporting, the estimation of the amount of under-reporting was as follows:
1. Across the three previous surveys (2000, 2003 SCS and 2004 SCVS7), there is a fairly stable relationship between the proportion of 17-39 year old drivers (2000 survey) or 17-39 year olds in the general population who had ever used drugs and the proportion who had used drugs in the previous 12 months. Across the three surveys, the proportion of respondents who had ever used drugs who also reported using drugs in the previous 12 months was 41%.
2. It assumes that, were it not for under-reporting, the same relationship would exist in 2005 and that about 41% of respondents who had ever used drugs would also have used drugs in the past 12 months.
3. Since 39% of 17-39 year drivers reported ever having used drugs in 2005, if 41% of them had also used drugs in the previous 12 months, this would suggest that the figures for drug use the past 12 months should be around 16% - almost double the 9% actually recorded in the survey.
Estimating the extent to which drug use might have been under-reported in relation to previous surveys is important for two reasons. First, it says something about the social acceptability of reporting drug use. The implication of the findings is that, compared with 2000, it has become less acceptable for drivers aged 17-39 years to report recent drug use. Second, the under-reporting will have a knock-on effect on the estimate of drug driving, since the structure of the questionnaire means that only people who have reported using drugs in the previous 12 months were asked if they had driven shortly after taking drugs. The implications of under-reporting drug use are discussed below.
Although an attempt has been made to estimate the amount of under-reporting, no adjustment of the survey data has been made to try to account for under-reporting, particularly in terms of respondent characteristics or behaviours. First, it is not certain that the survey is under-reporting although it appears likely to be. Second, while it is possible to estimate at an aggregate level, the accounting would need to be done for small sub-groups for it to make any difference to the survey results. It would be unreliable to calculate and apply weighting factors to the very small groups involved in this survey.
Types of drugs used
The overall estimates of drug use do not give information on the types of drugs that have been used in these periods. Due to the small number of respondents who reported drug use, it is necessary to look at different categories of drugs rather than individual drugs. For the purpose of this analysis, the drugs have been grouped into five main categories. This is similar to approaches that have been used in previous surveys and identical to the approach adopted by the 2000 drugs and driving survey to enable comparison across the surveys.
Table 3.1: Categorisation of drugs for analysis
Cannabis/ smoke (unknown)
CNS stimulants/ hallucinogens
The most commonly used category of drug was cannabis/smoke (unknown) with more than a third of respondents (35%) having tried these at some point in their lives. One in five (21%) had ever used drugs in the stimulants/hallucinogens category such as ecstasy and magic mushrooms. An increased proportion of respondents reported having ever used opiates in the 2005 survey compared with the 2000 drugs and driving survey (10% compared with 5%). No respondents reported use of Semeron, the bogus drug that was included to measure over-claiming.
The pattern of drug use is similar for the previous twelve months, as cannabis is also the most commonly used drug (7%). Similar proportions of respondents reported having used drugs in the stimulants/hallucinogens, opiates and suppressants categories.
Table 3.2 Categories of drugs taken ever/ past twelve months
Past twelve months
Base: All drivers 17-39 years (1,031)
Respondents were also asked how often they took drugs. The numbers for each category are too small to report so only the numbers for cannabis are reported. Forty-three percent of those who reported using cannabis in the previous twelve months said they had done so once a month or more often. The most substantial change between 2000 and 2005 is the significant increase in the proportion of drug users who said either they didn't know or couldn't remember how often they took cannabis. In 2005, the proportion of "don't know/can't remember" responses is five time higher than in 2000 (15% compared with 3%). Similarly, twice as many respondents refused to answer the question than in 2000. This fits with the suggestion that there is more of a stigma attached to drug use than in 2000 that is resulting in under-reporting or refusal to report accurately.
Table 3.3 Frequency of use of cannabis
Frequency of use
All past twelve month cannabis users 2005
All past twelve month cannabis users 2000
Once a week or more often
Two or three times a month
Once a month or more often
Once every three months
Once or twice a year
Don't know/can't remember
Base: (All drivers who reported use of cannabis users)