Substance use in adolescence is linked to mental illness in adulthood
Researchers have followed 68,000 teenagers for eight years to examine how different patterns of alcohol and drug use among young people are associated with mental illness, hospital admissions related to alcohol and drug use, as well as self-harm and suicide attempts later in life.
Young people who start drinking and using drugs early – and who use multiple substances – are at significantly higher risk of developing mental disorders, being hospitalized for alcohol- and drug-related causes, and engaging in self-harm and suicide attempts.
This is shown in a new study from the National Institute of Public Health, recently published in the scientific journal The Lancet Public Health.
The study is based on questionnaire responses from 68,301 Danish youth aged 15–19, collected in 2014 from high schools and vocational schools across the country. Based on their responses, researchers identified four overall patterns of substance use that appeared to be the same for boys and girls:
• A group that only drinks alcohol and often in smaller quantities – i.e., 0–9 drinks per week (48.8%).
• A group that frequently binge drinks – that is, drinks five or more drinks on one occasion (23.3%).
• A group that frequently binge drinks, smokes occasionally, and experiments with cannabis and other tobacco or nicotine products (16.3%).
• And a group that had already tried being drunk and smoking cigarettes before the age of 13, and who frequently binge drink, smoke daily, and experiment with various substances, such as cannabis and cocaine (11.6%).
The researchers then followed the young people for eight years, until they were adults aged 23–27, and linked their questionnaire data with national register data on hospital contacts and prescriptions for medications.
Difficult life circumstances
Young people in the two groups with either experimental or early and multiple substance use often also had difficult life circumstances, such as economic challenges at home, poor well-being at school, and parents with mental health issues, alcohol problems, or divorce in the family.
Elisabeth Reichel Hansen, research assistant and co-author of the study, explains:
“These are young people who were already struggling – and where the problems piled up. Their substance use can be seen as part of a broader vulnerability, where multiple stressors are interlinked and reinforce each other.”
Stood out significantly
One group in particular stood out – those with early and extensive use of multiple substances. As adults, they had a much higher risk of being hospitalized due to, for example, alcohol or drug poisoning.
“Compared to young people who only drink alcohol, the group with early and extensive substance use had more than 10 times higher risk of a hospital contact related to drug use and three times higher risk of suicidal behavior,” says Elisabeth Reichel Hansen.
They also had a 58% higher risk of receiving a psychiatric diagnosis or being prescribed psychotropic medication for conditions like anxiety or depression.
Protective factors
Somewhat surprisingly, the group of young people who frequently binge drank – that is, drank five or more drinks on a single occasion – had a lower risk of mental illness and suicidal behavior than those who drank alcohol only in small amounts.
The researchers cannot say for certain what explains this.
However, at the beginning of the study, the group of frequent binge drinkers reported higher life satisfaction and better socioeconomic conditions than the group with lower consumption.
According to Professor Janne Tolstrup, who studies alcohol prevention and helped conduct the study, this points to the importance of understanding young people’s substance use in the context of their life circumstances:
“It’s not the consumption itself that we believe is protective, but rather some of the life circumstances that this group appears to have,” she says.
Consequences in adulthood
Of the young people who participated in the study, 1,185 were hospitalized due to alcohol-related issues, and 9,425 received a psychiatric diagnosis or were prescribed psychotropic drugs during the eight-year study period.
The researchers hope that the findings will be used to guide targeted prevention efforts.
“The study documents that there are often underlying reasons why young people use multiple substances and start early. It often connects to other life challenges – that is, among those who are already struggling, we see a clustering of problems. And we also see serious consequences that carry into adulthood. That’s why it’s important to intervene early – especially for the most vulnerable groups,” says Janne Tolstrup.
Contact:
Research Assistant Elisabeth Reichel Hansen, phone: +45 6044 0551, email: elis@sdu.dk
Professor Janne Tolstrup, phone: +45 2076 4819, email: jest@sdu.dk
National Institute of Public Health, University of Southern Denmark