Non-suicidal self-injury is a prevalent and pressing public health concern, especially among young people. In recent decades, psychiatric research has greatly developed our understanding of the aetiology of self-injury and effective avenues for clinical intervention. However, the field has scarcely acknowledged the gender bias which pervades the self-injury literature – research has focused primarily on teenage girls and young women, at the exclusion of men and gender non-conforming people. In this dissertation, I revisit the topic of gender in self-injury research and use cross-sectional statistical analyses to address unanswered questions about gender similarities and differences in the prevalence, clinical severity, and functions of self-injury.

I begin by introducing the study of self-injury and current understandings of how psychological distress, emotion dysregulation, and impulsivity contribute to the behaviour. Next, I discuss the gendered origins of our modern knowledge and present some of the gender- based assumptions that pervade the literature. This lays the foundation for subsequent chapters to investigate the aetiology of gender disparities in self-injury prevalence and characterise gender similarities and differences in self-injury presentation.

I then present four quantitative studies across two community samples of young adults. The first study uses mediation and moderation analyses to test how self-reported psychological distress, emotion dysregulation, and impulsivity contribute to higher rates of self-injury among women than men. In the second study, these analyses are replicated in a second sample and extended to include gender non-conforming young adults, who report especially high rates of self-injury. The third study investigates whether gender differences in prevalence mirror differences in clinical severity by comparing groups on the reported addictive features of their self-injury, strength and intensity of urges, latency, and age of onset. The fourth study compares gender groups on their endorsement of 24 intrapersonal and social self-injury functions, and tests hypothesized group similarities and differences based on findings from previous chapters.

Across the four studies, results are consistent with a priori hypotheses and suggest gender disparities in levels of psychological distress and emotion dysregulation contribute to group differences. Gender non-conforming participants consistently emerge as the highest risk group, highlighting the need for self-injury research to address its neglect of this population. Overall, this dissertation provides novel insights into the aetiology of gender differences in self-injury and reveals key directions for future gender-informed research.