What Are the Characteristics of NSSI?
What We’ve Known
Beyond course, the field has some knowledge of the basic characteristics of NSSI. In terms of NSSI frequency, studies among representative adolescent and college-aged community samples indicate that most self-injurers report fewer than 10 lifetime instances of NSSI.3,31 However, frequency rates vary depending on the clinical severity of the sample. For instance, one study in a large-scale representative sample found that among adolescents meeting criteria for the DSM-5 NSSI disorder (i.e., more clinically significant NSSI), 75% of self-injurers engaged in more than 11 instances of NSSI in the past year.17 Moreover, NSSI frequency is even higher among inpatient clinical samples, where the majority of individuals report more than 20 lifetime episodes of NSSI.36
Overall features of NSSI severity are less clear given the range of measurement techniques used across studies. NSSI method is often used to index medical severity, meaning that NSSI severity is based on the potential degree of tissue damage (e.g., cutting and burning are more severe than pinching or interfering with wound healing). Using this method, studies have found that 50% of college student37 and adolescent34 self-injurers reported moderate to severe tissue damage, with higher rates of tissue damage reported among clinical samples.38 Other studies use self-report items that assess whether medical attention was received or injuries were more severe than intended. Based on this method, 50% of adolescents and college students reported needing “first-aid” and injuring “more severely than expected” one or more times,35
and around 25% reported they “should have shown injuries to a medical professional.”3 However, a much smaller percentage of individuals report actually seeking medical attention for their NSSI.16
Several studies have found that many self-injurers report feeling little to no pain during NSSI36,39 and have a higher pain threshold than both noninjurers40 and self-injurers who report feeling pain during NSSI.41 However, it should be noted that increased pain tolerance is not specific to NSSI; individuals who engage in more indirect forms of self-injury (e.g., drinking and disordered eating) also report higher pain thresholds.42
What We’ve Learned
To address limitations of retrospective self-reports, researchers have begun using ecological momentary assessment (EMA) techniques to understand characteristics of naturally and spontaneously occurring NSSI. These methods allow researchers to ask individuals about various characteristics, antecedents, and consequences of a self-injurious act within seconds or minutes of the episode, rather than weeks or months later. With EMA, individuals complete questionnaires on mobile electronic devices (e.g., Palm Pilots, cell phones) either when a signal notifies them to respond (i.e., signal-contingent entries) or following specific thoughts or behaviors, such as after NSSI (i.e., event-contingent entries).
Through use of EMA techniques, we have learned previously unavailable information about features of NSSI thoughts (e.g., intensity and duration) and about characteristics of the thoughts and emotions that precede and follow an NSSI episode. For instance, EMA studies have revealed that NSSI thoughts are transient: 85% of NSSI thoughts last less than an hour, and 25% last less than 1 minute (regardless of whether the thought led to actual NSSI).32 In one EMA study, self-injurers reported thinking about NSSI once a day and engaging in NSSI twice a week, with thoughts and behaviors rarely occurring under the influence of alcohol or drugs. Self-injurious acts were more likely to follow NSSI thoughts that were shorter in duration (i.e., 35% less than 1 minute; 75% less than 30 minutes), but higher in intensity.32 EMA studies have also revealed the affective states that precede and follow NSSI: prior to NSSI, individuals report an increase in negative affect (e.g., guilt, anger, hostility, and general negative affect) and reduction in positive affect, whereas following NSSI, individuals report a reduction in negative affect and increase in positive affect.43,44 Interestingly, one study found that although negative affect steadily increased more than 7 hours before a self-injurious event, self-injurers reported spending less than an hour preparing to self-injure.43 These findings suggest that individuals may go several hours unaware of the association between increasing negative affect and an impending NSSI event, thus highlighting the limitations of self-report, even real-time self-report.
What We Need
There remains a significant lack of knowledge regarding many basic characteristics of NSSI for several reasons. First, differences between studies make it difficult to aggregate findings. For example, studies reporting NSSI characteristics differ in time frame (lifetime vs. past year), sample (clinical, community, or epidemiological), and age (children, adolescents, college-aged adults, and adults). Second, studies have used different approaches to report the same basic characteristics. For instance, in terms of NSSI frequency, studies either use different frequency groupings (2-5 or 2-10 instances), report only an average frequency, or use markedly different upper limits (>10, >20, or >100). In addition, studies differ in the assessment of NSSI severity and decisions about which NSSI behaviors are severe enough to be included as NSSI. Third, many studies fail to collect or report any basic characteristics of NSSI.
What the field needs now is research that specifically addresses these limitations and gaps in knowledge. First, to the extent that they can, researchers should make data publicly available. This will greatly facilitate data aggregation and eliminate obstructions caused by reporting or sample differences. Second, the inclusion of clear and consistent questions about NSSI characteristics (frequency, severity) in large-scale epidemiological surveys will lead to more representative and accurate descriptions of NSSI. Third, research methods with greater temporal resolution, such as EMA and real-time physiological measures, should be used to further clarify more proximal characteristics (triggers, antecedents, and consequences) of NSSI.