Scottish Crime and Justice Survey 2014/15: Drug Use

Chapter 1: The Scottish Crime and Justice Survey

1.1 Introduction

The Scottish Crime and Justice Survey ( SCJS) is a large-scale social survey which asks people about their experiences and perceptions of crime. The 2014/15 survey is based on around 11,500 face-to-face interviews with adults (aged 16 or over) living in private households in Scotland.

The main aims of the SCJS are to:

• Enable the Scottish population to tell us about their experiences of, and attitudes to, a range of issues related to crime, policing and the justice system; including crime not reported to the police;
• Provide a valid and reliable measure of adults' experience of crime, including services provided to victims of crime;
• Examine trends, over time, in the number and nature of crimes in Scotland, providing a complementary measure of crime compared with police recorded crime statistics;
• Examine the varying risk and characteristics of crime for different groups of adults in the population.

The findings from the survey are used by policy makers across the public sector in Scotland to help understand the nature of crime, target resources and monitor the impact of initiatives to target crime. The results of this survey provide evidence to inform National Outcomes and Justice Outcomes.

This report presents findings from the self-completion module on illicit drug use ^[2] . The report provides data and analysis on self-reported illicit drug use in the last month, in the last year and ever among adults aged sixteen and over in Scotland.

1.2 Survey Design

The design of the 2014/15 SCJS remains broadly similar to the design of the SCJS from 2008/09 to 2012/13:

• Survey frequency : Following the completion of the SCJS 2010/11, the SCJS moved to a biennial design. Therefore, no survey ran in 2011/12 or 2013/14 ^[3] .
• Sample: the sample is designed to be representative of all private residential households across Scotland (with the exception of some of the smaller islands). A systematic random selection of private residential addresses across Scotland was produced from the Royal Mail Postcode Address File ( PAF) and allocated in batches to interviewers. Interviewers called at each address and then selected one adult (aged 16 or over) at random from the household members for interview.
• Questionnaire: the questionnaire consists of a modular design completed by the interviewer using Computer-Assisted Personal Interviewing ( CAPI) and a self-completion section covering sensitive crimes using Computer-Assisted Self Interviewing ( CASI). The most recent questionnaire is available on the SCJS webpage. Questions on illicit drug use were included in the self-completion section of the questionnaire, which was undertaken at the end of the main SCJS interview.
• Interviews and response rate: 11,472 face-to-face interviews were conducted in respondents' homes by professional interviewers, with a response rate of 63.8%. Interviews lasted an average of 40 minutes, though there was variation in interview length, depending on the respondent's reported experience. Additional to the main questionnaire, all survey respondents were asked to fill out a self-completion section (on a tablet computer) on more confidential and sensitive issues, including drug taking, partner abuse, sexual victimisation and stalking. In 2014/15, 9,986 respondents completed the self-completion module, that is 87% of all respondents. The most common reason for refusing to complete the self-complete questionnaire was 'running out of time' (mentioned by almost half of respondents who refused); more details are provided in the Technical Report (section 6.6.2). An equal proportion of men and women answered the self-completion questionnaire. However, the proportion of those who completed the self-completion section decreased with age. Further information on response rates can be found in the Technical Report (section 3.4).
• Fieldwork: interviews were conducted on a rolling basis between 1 ^st April 2014 and 31 ^st May 2015, with roughly an equal number of interviews conducted in each month between April 2014 and March 2015. Challenges in fieldwork delivery were experienced in 2014/15 and as a result, the fieldwork period was extended by two months to increase the achieved sample size.
• Weighting: the results obtained were weighted to correct for the unequal probability of selection for interview caused by the sample design and for differences in the level of response among groups of individuals. Given that not all respondents chose to answer the self-completion questionnaire, these data are weighted separately to the main questionnaire (using identical weighting procedures). Further details of the weighting used are provided in the Technical Report (section 4).

1.3 Survey Coverage

The SCJS does not aim to provide an absolute estimate for all crime and has some notable exclusions. The SCJS is a survey of adults living in private residential households and, therefore, does not provide information on crimes against adults living in other circumstances (for example those living in institutions or communal residences, such as prisons or hospitals, military bases and student accommodation). Those living in some of the smallest inhabited islands in Scotland are excluded for practical reasons (see Annex 1 of the accompanying Technical Report for details).

1.4 Drug Use

The main aim of the self-completion illicit drug use questionnaire was to establish whether adults aged 16 or over reported illicit drug use over three different time periods: at some point in their lives ( ever), in the last year and in the last month before the survey interview. In this report, the relevant reference period for each estimate discussed at any given point is presented in italics for clarity. The respective strengths and weaknesses of the respective time periods are as follows:

1. Self-reported use ever: whether respondents had used specific drugs at some point in their lives, providing useful contextual information when, for example, examining general attitudes to drugs. However, this is not a useful indicator of current drug use or recent trends since it can include people who have used a drug once, perhaps a long time ago.

2. Self-reported drug use in the last year: whether respondents had used specific drugs in the year prior to interview. This time frame is generally regarded as the most stable measure of current drug use, especially when analysing trends over time.

3. Self-reported drug use in the last month: whether respondents had used specific drugs in the month prior to interview. This time frame provides the most up-to date information on usage. It is particularly focused on when considering drug dependency. However, since it is a relatively short time period it is more prone to variation, for example, it may miss people who use drugs regularly but who have not done so within the last month.

The reference period ' in the last year' is mainly reported as it is generally regarded as the most stable measure of current drug use, especially when analysing trends over time. Information on drug used ever and in the last month are included in some figures and charts where relevant and can be found in more detail in the published web tables at: http://www.gov.scot/Topics/Statistics/Browse/Crime-Justice/Datasets/SCJS

In the SCJS 2014/15 respondents were asked whether they had taken 18 specific drugs. The overwhelming majority of the drugs asked about are illicit, but the list also included: prescribed drugs used illicitly ^[4] , poppers, glues, solvents, gas or aerosols and two 'new' drugs which are not controlled: salvia divinorum and nitrous oxide. In addition, respondents were also asked separately whether they had ever used 'new psychoactive substances', also known as 'legal highs'. This generic question about new psychoactive substances was included for the first time in the SCJS 2014/15. It is recognised that some people may report taking particular drugs when they have not actually done so. Respondents were asked whether they had taken a fictional drug 'semeron' and fourteen respondents who said they had taken this were removed from the analysis (making the overall sample 9,972 respondents). Those who had used any types of drugs were then asked a series of follow-up questions. Further details of the questionnaire content can be found in Annex 2 ( section A.2.2).

This report presents results on adults using drugs, over time, their characteristics and frequency of use etc. For simplicity and consistency, these results are generally presented as proportions of adults, however, to provide additional context on the scale of drug use, these proportions have also been grossed up to provide the estimated number of adults using drugs in the last year by drug classification, as presented in Annex 1 - Table A1.1 .

1.4.1 Classification of drugs

The Misuse of Drugs Act 1971 classifies illegal drugs into three categories (Class A, B and C) according to the harm they cause. The 18 drugs that respondents were asked about and their classification under the Act are:

• Class A, including cocaine, crack, crystal meth, ecstasy, LSD, magic mushrooms, heroin and methadone and amphetamines (if prepared for injection) ^[5] ;
• Class B, including amphetamines (in powdered form), cannabis, ketamine and mephedrone;
• Class C, including temazepam, valium and anabolic steroids;
• Not classified ^[6] , including poppers and glues, solvents, gas or aerosols;
• 'New' drugs ^[7] , including salvia divinorum and nitrous oxide.

Changes to classifications in 2014/15

Reflecting changes in legislation, some of the drug classifications used in this report differ from those used to produce the 2012/13 SCJS Drug use Report. These are described below.

Ketamine

Ketamine was reclassified from a Class C to a Class B drug under the Misuse of Drugs Act, with effect from June 2014. This change occurred during the fieldwork period for the 2014/15 survey. As a result, ketamine is presented as a Class B drug in this report. Previously, and as set out in section 1.5 of the 2012/13 report, ketamine was reported as a Class C drug. The effects of the change in approach to the classification of ketamine in 2014/15 is shown in the table below.

Adults self-reporting use of Class B and Class C drugs, ever and over the last 12 months, with and without changes to the classification of ketamine, 2014/15

Percentage of all adults	Last 12 months		Ever
	(Ketamine in Class B)	(had Ketamine remained in Class C)	(Ketamine in Class B)	(had Ketamine remained in Class C)
Class B	5.2	5.1	20.6	20.5
Class C	0.5	0.6	2.6	3.3

The effect of moving ketamine from Class C to Class B has made a difference of 0.1 percentage point to most categories. The exception is the change in use of Class C drugs ever, for which the move of ketamine from Class C to Class B means a reduction in Class C usage from 3.3% to 2.6%. It should be noted that, in effect, this means that had ketamine not moved from Class C to Class B in 2014/15, the change in Class C use ever would have been from 3.8% in 2012/13 to 3.3% in 2014/15, which is a not a statistically significant change (rather than from 3.8% to 2.6%, as noted in Section 2.3.2 and Table A1.3A).

Mephedrone

Mephedrone has been classified under the Misuse of Drugs Act 1971 since April 2010. It was first was added to the SCJS in 2010/11, as a 'new' drug. In order to ensure consistency with previous sweeps of the SCJS, it was excluded from the overall analysis and the trend analysis, and was reported separately in previous SCJS. However, reflecting its classification under the Misuse of Drugs Act, it has now been added to Class B in 2014/15 in this report. The additional effect of adding mephedrone to Class B in 2014/15 is very small; without mephedrone in Class B, Class B estimated use ever would be 20.5% rather than 20.6%, while estimated use in the last month would remain at 5.2%.

'New drugs'

Questions on the use of individual 'new drugs' have been included in the last two surveys, although the specific substances have changed over time. It is therefore not possible to make comparisons between reported use of any 'new drugs' in the SCJS 2014/15 and previous surveys.

In addition to reporting by Class, a number of other composite drug groups are reported. These composite groups, and the individual drugs that they include, are:

• Opiates, including heroin and the illicit / non-prescribed used of methadone;
• Stimulant drugs, including cocaine, crack, crystal meth, ecstasy, amphetamines and poppers;
• Psychedelics, including LSD, magic mushrooms and ketamine;
• Downers / tranquilisers, including temazepam and valium.

The groups include illicit drugs across the legal classifications and reflect the drugs' shared properties, effects and characteristics, providing an additional measure to the class-based categorisation. For example, stimulant drugs may be used interchangeably by the same people at similar times and in similar settings. Drugs not included in the composite groups such as cannabis, anabolic steroids and glues, solvents, gas or aerosols, are included separately in appropriate figures where sufficient data are available to do this.

1.5 Conventions used in figures and tables

Each Figure or Table has a title, the data source (survey year etc.), a base definition and the unweighted number of respondents and, if relevant, a variable name. For example:

1.5.1 Percentages

Table row or column percentages may not sum to 100 due to rounding.

Percentages presented in tables and figures where they refer to the percentage of respondents, households or crimes that have the attribute being discussed may not sum to 100 per cent. Respondents have the option to refuse answering any question they did not wish to answer and the majority of questions have a 'don't know' option. Percentages for these response categories are generally not shown in tables and figures.

A percentage may be quoted in the report text for a single category that is identifiable in the figures/tables only by summing two or more component percentages. In order to avoid rounding errors, the percentage has been recalculated for the single combined category and therefore may differ by one or two percentage points from the sum of the percentages derived from the figures/tables.

Also, percentages quoted in the report may represent variables that allow respondents to choose multiple responses. These percentages will not sum to 100 per cent with the other percentages presented. They represent the percentage of the variable population that select a certain response category.

1.5.2 Table abbreviations

' - ' indicates that no respondents gave an answer in the category.

'n/a' indicates that the SCJS question was not applicable or not asked in that particular year.

'0.0' indicates results of less than 0.05%

' bold text' indicates that changes are statistically significant at the 95% level.

1.5.3 Decimal places

Results from the self-complete section of the survey are generally reported in this document to one decimal place. The self-complete questionnaire collects information on a range of often rare events, therefore, many of the figures reported are small (often under 1%). There is a range of uncertainty around all survey estimates. As outlined below (in section 1.6), statistical testing is conducted to assess whether changes and differences between survey results are statistically significant. Only changes and differences which have been tested and assessed as being statistically significant are highlighted as such in this report.

1.6 Survey error and statistical significance

There may be errors in the recall of participants as to when certain incidents took place, resulting in some crimes being wrongly included in, or excluded from, the reference period. A number of steps in the design of the questionnaire are taken to ensure, as far as possible, that this does not happen, for example repeating key date questions in more detail.

The SCJS gathers information from a sample rather than from the whole population and, although the sample is designed carefully, survey results are always estimates, not precise figures. Estimates can differ from the figures that would have been obtained if the whole population had been interviewed.

It is, however, possible to calculate a range of values around an estimate, known as the confidence interval (also referred to as margin of error) of the estimate. At the 95 per cent confidence level, over many repeats of a survey under the same conditions, one would expect that the confidence interval would contain the true population value 95 times out of 100. This can be thought of as a one in 20 chance that the true population value will fall outside the 95 per cent confidence interval calculated for the survey estimate.

Because of this variation, changes in estimates between survey years or between population subgroups may occur by chance. In other words, the change may simply be due to which adults were randomly selected for interview.

We are able to measure whether this is likely to be the case using standard statistical tests and conclude whether differences are likely to be due to chance or represent a real difference in the underlying population.

Many of the tests for statistical significance in this report, particularly when examining results by different demographic sub-groups, were carried out using the Pearson chi-square test in SPSS ^[8] , based on individual scaled data. All significant changes highlighted in this report were found to be statistically significant at the p ≤ 0.05 level.

The assessments of statistical change over time which are presented in this report use estimated confidence intervals around survey results to examine whether the change is statistically significant. The estimated confidence intervals used in these tests and elsewhere in tables and charts in the report use a generic SCJS design factor of 1.2 for 2014-15 results. More detail on the derivation of these confidence intervals and design factors is available in Chapter 11 of the SCJS Technical Report.

Only increases or decreases that are statistically significant at the 95 per cent level are described as changes within this report and in the tables and figures these are identified by in bold text. Where no statistically significant change has been found between two estimates, this has been described as showing 'no change'. The presentation of uncertainty and change in this report reflect best practice guidance produced by the Government Statistical Service ( GSS) ^[9] .

1.7 Accessing Survey Data

Information on how to access SCJS data is available on the Data Access section of our webpage. SCJS Additional Datasets released alongside this report, present more detailed results from the survey questionnaire, showing how answers to questions vary when respondents are grouped by certain geographic, demographic, attitudinal or experiential characteristics.

1.8 Structure of the Report

The report proceeds as follows:

Chapter 2 focuses on prevalence of illicit drug use in Scotland exploring trends in self-reported drug use from the SCJS 2008/09 to the SCJS 2014/15, in comparison to the Crime Survey for England and Wales 2014/15, and looking at self-reported drug use by drug composite group, legal classification and specific drug type. This chapter also examines variations in self-reported drug use by demographic, socioeconomic and geographical factors. Lastly this chapter focuses on prevalence of being offered drugs and the prevalence of new pyschoactive substances.

Chapter 3 focuses on the experiences of those who reported drug use. This chapter begins by examining self-reported drug use in the last year with regards to specific drugs, polydrug use and joint use of alcohol and drugs. This chapter then examines experience of drug use ever by specifically looking at the age at which drugs were first used; the drug first used; and methods of taking drugs. Chapter 3 concludes by specifically focusing on the experiences of adults over 16 who have used one or more drugs in the last month looking at frequency of use; drug dependency; ease of obtaining drugs in the last month; and accessibility of drugs.

Annex 1 contains additional data tables showing the percentage of adults who reported taking illicit drugs in the last month, in the last year and ever. Further tables which show the data broken down by a range of demographic, experiential and area-related variables are available at: http://www.gov.scot/Topics/Statistics/Browse/Crime-Justice/Datasets/SCJS

Annex 2 provides further information on the methods employed in the SCJS 2014/15, focussing specifically on the self-completion questionnaire. This includes information on the questionnaire, disclosure of sensitive information, drugs classification, interview techniques, and the weighting used in the analysis of the results.

Annex 3 provides information on the strengths and limitations of the SCJS and the self-completion questionnaire.