People of all ages, genders, ethnicities, and social classes self-injure, though experiences such as racism and poverty increase risk. Below, we summarise some key factors that can relate to who self-injures.
Current research suggests that self-injury most commonly begins between ages 12 and 15 (Plener et al., 2015), with a second onset peak in early adulthood, around age 20 (Ghandi et al., 2018). Some people first start to self-injure before the age of 12 and some first self-injure much later in life. An age of onset before 12 is associated with more severe self-injury over a longer period of time (Muehlenkamp et al., 2019). Typically rates of self-injury increase through early-mid adolescence and decline in later adolescence.
A 2014 meta-analysis showed that approximately 17% of adolescents, 13% of young adults, and 5% of adults report a lifetime history of self-injury. The lower rates reported into adulthood may be due to recall bias (not remembering experiences from earlier in life).
Sex, gender, and sexuality
A 2015 meta-analysis of 116 studies showed that girls and women are slightly more likely to self-injure than boys and men, with this gender difference particularly evident in clinical samples. Self-injury is also more common among individuals identifying within the LGBTQIA+ community, with rates 2-3 times that of heterosexual/cisgender individuals (Liu et al., 2019).
Culture and race
A majority of research to date has focussed on samples comprising mostly Caucasian individuals from Western societies. This has lead to a significant gap in our understanding of NSSI among individuals in underrepresented cultural and racial groups. Current knowledge suggests that self-injury is present across cultures and races. A 2015 study showed there may be differences in age of onset and function, but the differences are complicated by social and economic factors, often brought about by racism.
A 2015 meta-analysis found that risk factors for self-injury include depression, hopelessness, abuse, personality and eating disorders, and impulsivity. People who engage in self-injury report being more sensitive to interpersonal stress or conflict, and experiencing greater difficulty expressing and regulating their emotions. That being said, most people who engage in self-injury do not have a mental illness.
Whilst people who have experienced trauma, particularly during their childhood, are more likely to engage in self-injury (Liu et al., 2018), it is a myth that all people who self-injure have experienced childhood trauma.