High prevalence and early onsets: Legal and illegal substance use in an urban cohort of young adults in Switzerland (2022)

INTRODUCTION: Debates about the legalization of illegal substances (e.g., cannabis) continue around the globe. A key consideration in these debates is the adequate protection of young people, which could be informed by current prevalence and age-of-onset patterns. For Switzerland, such information is limited, which is particularly true for women, despite advanced political efforts to legalize cannabis. The objective of the current study was to investigate substance use prevalence rates and ages of onset in a community-representative sample of female and male young adults in Switzerland.
METHODS: Data came from the Zurich Project on the Social Development from Childhood to Adulthood (z-proso). In 2018, participants (N = 1,180, 50.8% females) were ~20 years old. Lifetime and past-year use of alcohol, tobacco, cannabinoids, stimulants, hallucinogens, opioids, and benzodiazepines were assessed with an extensive substance use questionnaire. Additionally, ages of onsets of the respective substances were estimated by averaging participants' self-reported ages of onsets from ages 13 to 20 (max. 4 assessments).
RESULTS: 57% of 20-year-olds had used cannabinoids, 16% stimulants, 15% opioids (mostly codeine), and 8% hallucinogens in the past year. Males had higher prevalence than females for most drugs; nevertheless, females' prevalence rates were notably high. Legal substance use was typically initiated 1.3-2.7 years before legal selling age. Thus, almost half of the sample had consumed alcohol and tobacco by age 14. More than 40% of the total sample had smoked cannabis by age 16. Males initiated use of legal substances and cannabis earlier than females.
DISCUSSION: Our recent community-representative data suggested unexpectedly high levels and early onsets of substance use compared to a previous Swiss surveys and also the European average. Drug policy debates should consider urban substance use patterns when considering legalization efforts.