Levels of self-harm and suicide rates are rising among young people. Substance misuse is one of the leading causes of harm in young people. Evidence from population-based longitudinal studies suggests that many young people who self-harm in adolescence do not persist with these behaviours into adulthood, either due to a natural decline in the behaviours or as a result of intervention. Substance use, however, tends to naturally increase into adulthood, reflecting increasing social norms as people reach the legal age of alcohol use. Substance misuse and self-harm are thought to share characteristics, as both can be conceived as behaviour used to cope with difficult underlying emotions but which can both cause serious harm to the self. Indeed, in clinical samples, self-harm and suicidal behaviours are often comorbid, however, there is a lack of research into the co-occurrence of these behaviours among young people living in the community.

In this study, we will describe the comorbidity of self-harm/suicidal behaviour and substance use from age 16 to 24, in order to see how these behaviours and their co-occurrence change over time. We will look at comorbidities between self-harm/suicidal behaviour and alcohol use, cannabis use and use of other illicit drugs.