Landmark study finds year of birth impacts on drug and alcohol use

June 2019

A landmark study of mental health and substance use among more than 90,000 people across 25 countries, published in JAMA Psychiatry, has found that an individual’s risk of commencing drug and alcohol use increases in line with the extent of substance use among people born in the same year. The association was independent of individual risk factors or immediate peer group behaviour.

The authors, led by researchers from the National Drug and Alcohol Research Centre (NDARC) at UNSW Sydney, say the findings suggest that any intervention to reduce substance use within a birth cohort will reduce an individual’s risk of commencing drug and alcohol use and therefore putting themselves at future risk of problematic use. However, once an individual starts substance use, the likelihood of developing problematic use and dependence is associated with individual risk factors, the study found.

Lead author, NDARC’s Professor Louisa Degenhardt said that the strength of the study, which analysed data from the World Health Organisation’s mental health surveys, was not only the size of the group but the breadth of the assessment, which asked about mental health disorders, substance use disorders and the age at which different events occurred.

Speaking to the ABC’s Norman Swann, Professor Degenhardt said the birth cohort effect was more about beginning use than developing problematic use.

“Once someone started using drugs, whether or not they became dependent on drugs was not related to what their peer group were doing in terms of levels of use, which suggests that getting into trouble with drugs says more about the individual than what their peers are doing.

“But what it also suggests is that if you are thinking about reducing that peer effect, what you want to do is prevent the onset of drug use for an individual and their peers.”

Listen to the interview on the ABC Health Report here.

Degenhardt, L., Bharat, C., Glantz, M. D., Sampson, N. A., Al-Hamzawi, A. ... & Kessler, R. C., for the WHO World Mental Health Survey Collaborators, Slade, T. (2019). Association of cohort and individual substance use with risk of transitioning to drug use, drug use disorder, and remission from disorder Findings From the World Mental Health Surveys. JAMA Psychiatry, Advance online publication. doi:10.1001/jamapsychiatry.2019.0163