What We Need
To understand the true prevalence of NSSI, the field needs more epidemiological studies using clear and consistent definitions of NSSI (e.g., using the DSM-5 proposed NSSI disorder criteria), standardized assessment tools that are acceptable across countries, high response rates, and representative samples. For instance, NSSI should be assessed in future waves of large-scale national and cross-national studies. Adopting this framework will provide more valid estimates of NSSI and allow for more reliable comparisons cross-nationally, between age groups, and over time.
What Is the Course of NSSI?
What We’ve Known
Understanding the natural course of any behavior is a basic descriptive step necessary for clarifying etiological mechanisms and for developing effective intervention and prevention programs. Unfortunately, because of a few key factors, there are significant gaps in our knowledge of the course of NS SI. First, NSSI is typically performed in private and difficult to observe directly.32 Second, NSSI research has relied almost entirely on retrospective self-report, a technique limited by biases and errors in memory. Third, few studies have employed designs with the temporal resolution necessary to shed light on the development of NSSI. Only a few longitudinal studies on NSSI have been conducted, and those have all used relatively short follow-up periods (i.e., <5 years).
What We’ve Learned
Despite these limitations, consistent research, in both clinical and community samples as well as cross-nationally, indicates that individuals typically begin engaging in NSSI between 12 and 14 years of age.17,19 Although many studies have collected data on the age of onset of NSSI, few have reported the duration of NSSI. One study found that among college students who had not self-injured in more than a year (and predicted they would not in the future), 40% reported a duration of less than 1 year and another 40% reported a duration of 1-5 years.3 In addition, recent findings from longitudinal research indicate that NSSI is relatively stable over time: in community samples of adolescents and college students, 50-63% continued to engage in NSSI over the subsequent 1-2 years.33-35 Factors that predicted continued engagement in NSSI included more severe history of NSSI (e.g., greater number of NSSI methods),33 depressive symptoms,34 and lack of social support.34,35 Although these findings are from only a few studies with relatively small samples over short follow-up periods, they provide initial evidence to suggest that, for a majority of self-injurers, NSSI does not remit quickly. Finally, although NSSI and suicidal behavior are distinct, growing research indicates that NSSI is one of the most robust risk factors for suicidal behavior.23,24 Clarifying the course of NSSI will be essential for elucidating how engaging in nonsuicidal behaviors confers risk for suicidal forms of self-injury.
What We Need
Other than the age of onset, the course of NSSI remains relatively unknown and should be an important focus of future research. For instance, we do not know how the frequency, methods, and medical severity of NSSI change over time: do less severe NSSI behaviors (e.g., biting, pinching, hair-pulling) lead to more severe behaviors (e.g., cutting, carving, burning)? Or do behaviors become more medically severe over time (e.g., deeper cutting)? Understanding the course of NSSI frequency and severity may help elucidate how NSSI leads to suicidal behavior. In addition, although preliminary evidence indicates that NS SI is relatively persistent over time, the field does not yet know how long these behaviors persist, for whom they persist, and what factors predict remission and recurrence of NS SI.
To improve understanding of NS SI course, the field needs: (1) large-scale studies with representative samples that follow individuals over long periods of time (e.g., from early adolescence to adulthood) to identify different NS SI trajectories (e.g., adolescent-limited vs. adult-persistent courses of NSSI), as well as factors that predict NSSI maintenance, remission, and recurrence, and (2) small studies with high-risk samples (e.g., adolescents in mental health treatment) that follow individuals more intensely or frequently over shorter time periods to assess changes in the frequency, method, and severity of NSSI, as well as NSSI features that increase risk for suicidal behavior.