Adolescence is a period of rapid biological and social change. The use of recreational substances, including alcohol, tobacco and cannabis, is widespread among adolescents. For some, adolescence and young adulthood are also the time when mental health difficulties emerge. This co-occurrence of substance use and mental health problems has attracted much research attention as to whether there is a causal link.

ALSPAC, like all longitudinal studies, suffers from attrition (over time, people drop out of the study) and non-response (those still engaged with the study may not complete every questionnaire, or every question within a questionnaire). If the likelihood of participating in ALSPAC is associated with substance use and mental health, analysis could lead to incorrect estimates of the association between them.

Linkage to administrative and health records is one approach to deal with attrition and non-response. In this proposed project, we plan to use data on mental health from participants' health records (e.g. GP records and hospital admissions) to investigate the association between self-reported substance use in adolescence and diagnosed mental health difficulties, particularly depression, anxiety and psychosis.