Background: Alcohol is a leading risk factor to adolescent health. However, it is unclear how associations between alcohol intake and injuries are shaped. We investigated the dose–response relationship between alcohol intake and risk of hospital contacts due to alcohol and unintentional injuries in adolescents.

Methods: We conducted a prospective cohort study including 71,025 Danish students aged 15–24 years, followed up for five years from 2014 to 2019. The main outcome measures were hospital contacts due to alcohol and unintentional injuries (all injuries and head injuries), obtained from hospital registers.

Findings: Approximately 90% of males and females reported drinking alcohol, and the median intake among those was 11 drinks/week in males and 8 drinks/week in females. During five years of follow-up, 1.3% had an alcohol-attributable hospital contact, the majority of which were due to acute intoxication (70%). Alcohol-attributable hospital contacts were equally frequent in males and females and between age groups (15–17-year-olds vs 18–24-year-olds). Compared with never drinking, the adjusted incidence rate ratios for weekly intake of <7, 7–13, 14–20, 21–27, and >27 drinks/week were 1.70 (95% confidence interval 1.23–2.34), 1.77 (1.27–2.46), 1.91 (1.35–2.70), 2.34 (1.59–3.46), and 3.25 (2.27–4.64) for having an alcohol-attributable hospital contact within five years of follow-up. Restricting follow-up to one year more than doubled risk estimates. During the five years of follow-up, 27% incurred an unintentional injury. The most frequent types of injury were to the wrist or hand (27.6%), ankle or foot (25.2%), or head (12.4%). Injuries were more frequent among males (first-time incidence rate 110 per 1000 person-years) compared to females (82 per 1000 person-years), with no differences between age groups. Compared with never drinking, the adjusted incidence rate ratios for weekly intake of <7, 7–13, 14–20, 21–27, and >27 drinks were 1.09 (1.03–1.15), 1.14 (1.07–1.20), 1.25 (1.17–1.33), 1.38 (1.28–1.49), and 1.58 (1.47–1.69) for having a hospital contact for any type of unintentional injury within five years of follow-up. Results for the one-year follow-up period were comparable. Separate analysis for head injuries showed similar results as the analysis on all injuries. Results were generally similar in males and females.

Interpretation: Adolescents’ drinking is associated with a higher risk of acute harm in terms of hospital contacts due to alcohol and unintentional injuries in a dose–response relationship. Thus, increased risk was apparent in those with low alcohol intake, suggesting a need for awareness of and initiatives to prevent youth drinking. Furthermore, initiatives should include a strengthened focus on people younger than 18 years.