Supplementary Material for: Drug Use Changes at the Individual Level: Results from a Longitudinal, Multisite Survey in Young Europeans Frequenting the Nightlife Scene

<b><i>Background:</i></b> Monitoring emerging trends in the increasingly dynamic European drug market is vital; however, information on change at the individual level is scarce. In the current study, we investigated changes in drug use over 12 months in European nightlife attendees. <b><i>Method:</i></b> In this longitudinal online survey, changes in substances used, use frequency in continued users, and relative initiation of use at follow-up were assessed for 20 different substances. To take part, participants had to be aged 18–34 years; be from Belgium, Italy, the Netherlands, Sweden, or the UK; and have attended at least 6 electronic music events in the past 12 months at baseline. Of 8,045 volunteers at baseline, 2,897 completed the survey at both time points (36% follow-up rate), in 2017 and 2018. <b><i>Results:</i></b> The number of people using ketamine increased by 21% (<i>p</i> &lt; 0.001), and logarithmized frequency of use in those continuing use increased by 15% (<i>p</i> &lt; 0.001; 95% CI: 0.07–0.23). 4-Fluoroamphetamine use decreased by 27% (<i>p</i> &lt; 0.001), and logarithmized frequency of use in continuing users decreased by 15% (<i>p</i> &lt; 0.001, 95% CI: −0.48 to −0.23). The drugs with the greatest proportion of relative initiation at follow-up were synthetic cannabinoids (73%, <i>N</i> = 30), mephedrone (44%, <i>N</i> = 18), alkyl nitrites (42%, <i>N</i> = 147), synthetic dissociatives (41%, <i>N</i> = 15), and prescription opioids (40%, <i>N</i> = 48). <b><i>Conclusions:</i></b> In this European nightlife sample, ketamine was found to have the biggest increase in the past 12 months, which occurred alongside an increase in frequency of use in continuing users. The patterns of uptake and discontinuation of alkyl nitrates, novel psychoactive substances, and prescription opioids provide new information that has not been captured by existing cross-sectional surveys. These findings demonstrate the importance of longitudinal assessments of drug use and highlight the dynamic nature of the European drug landscape.

**背景**：对日益动态化的欧洲毒品市场新兴趋势进行监测至关重要，但目前个体层面的变化相关信息仍较为匮乏。本研究针对欧洲夜场参与者的药物使用情况，展开了为期12个月的变化趋势调查。**方法**：本项纵向线上调查针对20种不同物质，评估了药物使用种类的变化、持续使用者的使用频率变化，以及随访阶段的相对新增使用情况。本研究的纳入标准为：参与者年龄介于18至34岁之间，来自比利时、意大利、荷兰、瑞典或英国，且在基线时的过去12个月内至少参与过6场电子音乐活动。本研究基线阶段共招募8045名志愿者，其中2897名参与者于2017年及2018年的两个时间点均完成了调查，随访应答率为36%。**结果**：氯胺酮（ketamine）的使用者人数增长了21%（*p* < 0.001），持续使用者的对数化使用频率提升了15%（*p* < 0.001；95%置信区间：0.07~0.23）。4-氟苯丙胺（4-Fluoroamphetamine）的使用比例下降了27%（*p* < 0.001），持续使用者的对数化使用频率降低了15%（*p* < 0.001，95%置信区间：-0.48~-0.23）。随访阶段相对新增使用比例最高的药物依次为合成大麻素（synthetic cannabinoids，73%，*N*=30）、甲氧麻黄酮（mephedrone，44%，*N*=18）、亚硝酸烷基酯（alkyl nitrites，42%，*N*=147）、合成解离剂（synthetic dissociatives，41%，*N*=15）以及处方类阿片类药物（prescription opioids，40%，*N*=48）。**结论**：在本项欧洲夜场参与者样本中，氯胺酮的使用量在过去12个月内增幅最大，且持续使用者的使用频率也同步提升。亚硝酸烷基酯（alkyl nitrates）、新型精神活性物质（novel psychoactive substances）以及处方类阿片类药物的摄入与停用模式，为现有横断面调查未覆盖的全新信息。本研究结果凸显了药物使用纵向评估的重要性，同时也揭示了欧洲毒品市场的动态变化特征。