ATTUNE is a cross-sectional mixed-methods study which seeks to explore the dynamics and trajectories of different ATS use patterns in Europe. In addition to systematic reviews of the existing qualitative and quantitative literature on ATS use, ATTUNE comprises two key components. First are the in-depth semi-structured interviews with ATS users and non-users to explore experiences with ATS over the life course and to identify key turning points in their consumption patterns. Second is the structured questionnaire administered by computer tablet to a larger sample of users and non-users to validate and generalise the qualitative interview findings.

The semi-structured interviews employed two topic guides: one for ATS users and one for non-ATS users who were exposed to ATS (defined as having been present when family or friends took ATS but did not consume themselves and have never taken ATS during their entire life course). The topic guides covered aspects of initiation, continuation and increase and decrease of ATS consumption. As part of these interviews, life course charts were used to help provide a chronological structure for discussions about ATS use over time and to capture more detailed data on participants’ living environment, health conditions, social functioning, life events and broader lifestyle. The life course charts were used here with the very specific intention of providing a more systematic means of recording valuable contextual data. Here we report exclusively on findings from the analysis of the life course data.

Ethical approval for data collection and use was secured in five of the six participating countries, and in the Netherlands, an ethical approval was not required. All participants received an information leaflet about the study, informed consent was then obtained and anonymity and confidentiality protected. The interviews were audio-recorded and transcribed in full. Trained and experienced fieldworkers implemented the interviews that lasted between 60 and 90 min. Participants also received a small incentive after the interview, by way of thanks for their time.

Life course charts

Life course charts have been used previously in qualitative research as a means of contextualising individual semi-structured interviews [25]. In the substance use field, life course charts are used to assess the intensity of drug use at critical time points in a participants’ history and to observe possible associations between critical life events and changes in the drug use trajectory. One particular study with substance using adolescents found that life course charts enhanced the memory of the respondents to recall their drug career and significant life events in chronological order [26,27,28]. A review of the use of calendar or timeline instruments demonstrated that these types of instruments contributed to improved data quality as they helped respondents relate specific events and dates to different behaviours and consequences [27].

Timeline instruments have the structure of a chart, with rows referring to the person’s life in years and columns representing different aspects of life (life domains) and substance use, which can vary by study [26, 27]. For this research, a life course chart was developed which reflected the overarching study objectives (see Fig. 1 in Appendix 1). This study used the following defined periods in an individual participants’ life course: until the age of 13, age 14–16, age 17–19, age 20–25, age 26–30, age 31–39, age 40–49 and age 50+. The chart included two separate sections, one referring to substance use and one referring to life events. The section on substances covered the use of different ATS, cannabis, cocaine, opiates and alcohol. The drug use pattern was recorded for each time period by asking users to identify how frequently particular substances were used out of the following five options: no use, use less than monthly, monthly use, weekly use or (almost) daily use. Where the frequency of use varied significantly within one time period, the most frequent use was entered into the life chart. The life event section included 11 different domains, including family history, education, friends, health and illness, involvement with the criminal justice system, substance use treatment and leisure.

The life course chart was implemented as part of the semi-structured, face-to-face interviews with ATS users and non-users. Whilst the life course chart provided interviewers with structured prompts to motivate the interviewer to ask for details of specific live events, the instrument itself was administered iteratively to reflect the fact that certain life events may not have been experienced by some respondents or were not felt to be especially significant. For each of the specific time periods and associated life domains, only one significant life event could be recorded. Where two key life events were reported for the same life domain and time period, the more critical negative life event was noted.

Sampling criteria and recruitment

To be eligible for inclusion, the first consumption or exposure to ATS needed to have been at least 5 years before the interview took place. Further inclusion criteria were that individuals should be: 18 years or older, have no opioid dependency in their lifetime (with five exceptions for the UK sample), resident in one of the five countries and able to participate in the interview. The inclusion criteria were reviewed with each individual via a standardised screening checklist and only eligible individuals were interviewed.

To ensure variation in ATS pathways and trajectories, we targeted five predefined groups of ATS users and a further group of non-users. Eligible interview participants were allocated to one of the study groups, depending on their consumption pattern, their ATS dependency level and current state of use (Table 1). Dependency was measured with the Severity of Dependence Scale (SDS), which is a five-item questionnaire that provides a score indicating the severity of dependence on amphetamines [29]. An ATS related SDS greater or equal four was approximated as dependency. Former ATS users (defined as not having used ATS in the last 12 months) were asked to fill in the SDS for the phase when their ATS use was the most intense in their life. Current ATS users related the SDS to the last 12 months, and if this result was negative, the SDS was administered again to relate to the most intensive phase.

Table 1 Operationalisation of the study groups Full size table

We aimed to purposively sample five participants per study group in the Czech Republic and 10 participants per group in the other four countries. Participants were recruited into the study using a number of recruitment strategies, including advertising the study by flyer, poster and social media, via contacts within drug and health services, and by interviewees who shared the study link within their networks (snowball sampling). The interviewees were asked how they learnt about the study and more than half of them (51%) were informed by friends or family members. Almost a quarter of participants were recruited by staff of drug treatment services (24%), a smaller number responded to the flyer and posters (16%) and the remaining interviewees heard about the study through social media or from researchers.

In total, 279 eligible participants across five countries participated in the interviews. However, the target sample for each study group could not be realised in all countries (Table 2). While in group 2 (FDU—formerly ATS-dependent users) the recruitment target was exceeded, group 4 (FFU—formerly frequent ATS users) proved difficult to access, especially in Germany and Poland.

Table 2 Sample size by country and study group Full size table

The interviews were performed by national experienced expert teams. All interviewers were familiarised with the interview materials prior to data collection, all guidance materials were utilised and translated into the national languages where applicable. The Czech partner engaged three well-experienced qualitative researchers, two on post PhD employment; in Germany, the team comprised of three post PhD and two senior researchers; in the Netherlands, experts comprised two persons with experiences in qualitative interviewing, one with MSc and one PhD; in Poland, the team was led by an assistant professor (15 interviews) supported by one experienced university researcher, two experienced external interviewers and two well-trained university co-workers. For the UK, all interviewers were experienced in qualitative interviewing (two post PhD and one MSc) and completed the National Institute for Health Research Good Clinical Practice training.

Characteristics of the participants

41.2% of the participants were female, and the mean age of all participants was 31 years (Table 3). On average, exposure and use of ATS first occurred when participants were 18 years old. More than a third of participants had, at some point, been in contact with drug treatment services (39.4%), in particular those from group 1 (currently dependent) and group 2 (formerly dependent). SDS screening scores confirmed that participants in group 1 (currently dependent) and group 2 (formerly dependent) were severely dependent, with mean SDS scores of 7.2 and 7.3, respectively [30]. Overall, 33.9% of the sample had ever used ATS (almost) daily, 43.7% of the ATS users consumed (almost) daily or at least weekly amphetamines within the given time periods, but with huge differences among the groups. Daily or weekly amphetamine use was highest in group 1 (currently dependent) at 80.9%, and lowest in group 5 (non-frequent) at 22.4%. In groups 1 (currently dependent) and 2 (formerly dependent), 21.3% and 30.4% took methamphetamines frequently, but no use was reported from group 5 (non-frequent). Daily or weekly MDMA use was evidence in around 30% of the ATS users, but again, group 5 (non-frequent) had the lowest rate of frequent MDMA use.

Table 3 Characteristics of the interviewees by study group Full size table

Across all ATS user groups, more than 90% reported lifetime cannabis use, even in group 6 (non-ATS users, at almost 80%). More than half of all respondents reported lifetime cocaine use, with the prevalence highest in group 4 (former frequent) and lowest in group 6 (non-ATS users) at 83.8% versus 4.8%. With regard to alcohol consumption, around 40% of the sample report having ever drunk alcohol on a daily basis, rising to around half of respondents from the two ATS-dependent groups.

Analysis

A total of 3547 life events were documented in the life course charts for the 279 interviewees, each of which referred to the respective time period when the event occurred. The life events were extracted from the life course charts, with multiple same responses aggregated to a single entry and disconnected from any interviewee information. In order to analyse the life events, experienced researchers based in the respective national research institutions normatively rated each event either as positive, negative or neutral, where neutral means that the life event could not be rated as positive nor negative because according to the normative judgement of the national experts it was neither positive nor negative. As such, the meaning attributed to each event could reflect the cultural importance of certain life events in relation to each national field site, for example, marriage (positive in Poland), living with a partner (neutral in the UK, positive in other countries) and university degree (positive in Germany, neutral in the UK). Table 4 shows examples for the ratings in the defined 11 life domains. None of the interviewees ascribed any positive life event in the categories illness or criminal justice system.

Table 4 Examples for ratings of the life events according to the life domain Full size table

For each person, we calculated the cumulated sum of negative, positive and neutral life events at different points in time for all life domains together, as well as the sum for negative life events for every single life domain. An empty cell in the life course chart for life events was counted for the sum scores as zero. The sums of life events serve in our models as the dependent variable. For the analysis of the life events in the entire life course, we applied an age-adjusted factorial analysis of covariance ANCOVA, with the independent variables study group and country. For the analysis of life events while using ATS, we calculated a duration-adjusted ANCOVA in which for group 6 (non-ATS users) we determined the duration from age at first ATS exposition to the current age. For comparing the six groups (independent variable), we computed univariate analysis of analysis of variance (ANOVA) and ANCOVA in SPSS [31] and chose partial ETA squared as an indicator of the effect size, where 0.01 is considered as small, 0.06 as medium and 0.14 as large effect [32]. A p value of < 0.05 was employed to state statistical significance.

These data analysis were largely explorative, but the following hypotheses were guiding some parts of the analysis: