New research from Denmark unpacks how adolescent substance use (even “just” alcohol) can pave a dangerous path to future mental health crises. Clinicians, take note.
Adolescent experimentation with drugs is not uncommon, alcohol and tobacco tend to be the two most popular (and legally available) substances that young people try. A significant minority will also try illicit substances such as cannabis, cocaine and ecstasy for example. There is also data suggesting young people are using pharmaceutical drugs such as sedatives and tranquilisers without a prescription in what is referred to as non-medical use of prescription drugs (EUDA, 2025).
Understanding how adolescent substance use patterns predict mental health disorders is highly relevant for clinicians working with young people. There is a commonly held view by mental health professionals that there is a connection between young people’s drug use and the emergence of mental health problems. A new study in Lancet Public Health sought to explore this link and establish if adolescent drug use is a risk factor for mental health problems that develop in adulthood (Hansen et al, 2025).
Adolescent substance use is common and understanding its links to later mental health disorders would benefit clinicians working with young people.
Methods
This research drew on information available for young people in Denmark from national registers in 2014. The young people were between 15 and 19 years old. The sample was large and population-based, with 68,301 participants, of which 59.7% were female and 40.3% were male, and followed up over eight years. Robust linkage with national hospital and prescription registers strengthened the availability and objectivity of data. The focus of the authors was on adolescent drug use and any consequent contact with mental health services for a range of problems including eating disorders, depression, suicidal ideation and anxiety among others.
A range of related factors such as parental substance use, socio-demographic status and education were also collected.
Four patterns of substance use were characterised by the researchers:
- Alcohol use only
- Frequent binge drinking
- Experimental substance use
- Early-onset multiple substance use.
Results
A small proportion (8.6%) reported no alcohol and drug use. For the four groups characterised by the authors, alcohol proved to be the most used substance, which reflects the findings of other studies and surveys of young people. For those characterised as early-onset multiple substance use, most had used alcohol and tobacco as well as other illicit substances.
As may have been expected, a dose-response relationship was found between early drug use and mental health problems in adulthood. That is to say that the more substances a young person used the greater their risk of encountering services later due to mental health problems. For example, the hazard ratio for frequent alcohol use and later mental health difficulties was 0.87 and 1.58 for those in the early-onset multiple substance use group, compared with the alcohol-only group.
One striking finding with direct clinical implications is that adolescents in the early-onset multiple substance use group had a markedly higher risk of suicidal behaviour (HR 3.20) compared to the alcohol-only group. Clinicians may also note with caution that adolescents engaging in frequent binge drinking showed a slightly lower risk of mental or behavioural disorders compared to the alcohol-only group, though their alcohol use still warrants concern (HR 0.87).
The gender differences reported in this study are fascinating. For example, contrary to what many may think, young women were more likely to drink alcohol than young men, 52.2% versus 43.8%. Although young men were more likely to experiment with drugs than their female peers, 22.9% versus 11.8%.
The study showed a dose–response relationship between adolescent substance use and later mental health problems, with early-onset multiple substance use strongly linked to higher risks, including suicidal behaviour.
Conclusions
This is an important study that builds on previous research suggesting a clear link between adolescent exposure to substances and encountering mental health problems in the future.
There is a common perception that young men are more likely to use substances than their female counterparts, this research provides some interesting insights that challenge this view.
For clinicians, these results highlight the importance of early identification and tailored intervention for adolescents showing high-risk substance use patterns, which could help prevent severe mental health outcomes later.
Identifying and addressing high-risk substance use in adolescents could prevent serious mental health challenges in adulthood.
Strengths and limitations
It is encouraging to see gender included in the data and reported in the analysis. Although this may seem like a basic piece of information it is sadly not always included. Despite many journals and academic bodies saying they encourage including data on gender this continues to be an ambition rather than the norm (Bibb, 2022).
The authors acknowledge some limitations to their research. As they relied on follow-up data drawn from hospital contacts, they could have missed less severe or milder mental health problems. They also did not collect data on ethnicity so were unable to explore this important demographic detail. This means clinicians should remain alert to cultural and ethnic differences in substance use patterns that this study could not capture.
Taking these limitations into account, the authors assert that they could have underestimated the extent of the relationship between teenage drug use and adult mental health problems.
I’ll sit on the fence when it comes to the statistical methods and reporting, several of these were used. Some may think this is valid, but I found it a little confusing when it came to unpicking the results as it was difficult to compare different variables and outcomes.
This research may have underestimated milder cases and lacked ethnic subgroup analyses relevant for diverse clinical settings.
Implications for practice
This study provides crucial intelligence for practitioners as it points to the risks that early substance use poses to later mental health. In particular, the greater and more frequent use of substances and mental health problems. I’m sure many mental elves will have been aware of this, but it’s useful to have further evidence.
Clinicians working with adolescents could consider incorporating routine screening for early substance use patterns, with special focus on age of first use and types of substances tried. These results also support advocating for policies that delay the initiation of alcohol and drug use among young people, such as higher minimum legal drinking ages or tighter advertising restrictions.
For me one of the most useful findings is on gender differences, or the lack of difference in some cases. Convention says that young men are more prone to risk taking including experimenting with substances, while that remains partly true, this study provides some fascinating insights about where this is reversed, as it is young women who are at a greater risk. Highlighting not only that gender matters, but looking beyond the headline findings is also important.
Findings highlight the importance of prevention strategies and policy advocacy to delay substance initiation at young age.
Links
Primary paper
Elisabeth R Hansen, Sofie Kruckow, Sarah W Feldstein Ewing, Merete Nordentoft, Kristine Rømer Thomsen, Janne S Tolstrup. 2025. Adolescent substance use patterns and subsequent risk of mental and behavioural disorders, substance use, and suicidal behaviour: a cohort study. Lancet Public Health;10: e578-87.
Other references
Bibb, L.A., Adkins, B.D., Booth, G.S., Shelton, K.M. and Jacobs, J.W., 2022. Analysis of sex and gender reporting policies in preeminent biomedical journals. JAMA Network Open, 5(8), pp.e2230277-e2230277.
European Union Drug Agency, 2025. New ESPAD survey results: Teen substance use down, but new risks emerging. https://www.euda.europa.eu/news/2025/new-espad-survey-results_en