Nonsuicidal Self-Injury and Substance Use Disorders: A Shared Language of Addiction (2022)

Abstract: Nonsuicidal self-injury (NSSI), or the deliberate injuring of one?s body without intending to die, has been shown to exhibit many similarities to substance use disorders (SUDs), including population-level characteristics, impulsivity traits, and comorbidity with other mental disorders. Research has further shown that people who self-injure adopt language common in SUD recovery communities (e.g., “clean”, “relapse”, “addiction,” and celebratory language about sobriety milestones). In this study, we investigate the shared language of NSSI and SUD by comparing discussions on public Reddit forums related to self-injury and drug addiction. To this end, we build a set of LDA topics across both NSSI and SUD Reddit users and show that shared language across the two domains includes SUD recovery language in addition to other themes common to support forums (e.g., requests for help and gratitude). Next, we examine Reddit-wide posting activity and note that users posting in r/selfharm also post in many mental health-related subreddits, while users of drug addiction related subreddits do not, despite high comorbidity between NSSI and SUDs. These results show that while people who self-injure may contextualize their disorder as an addiction, their posting habits demonstrate comorbidities with other mental disorders more so than their counterparts in recovery from SUDs. These observations have clinical implications for people who self-injure and seek support by sharing their experiences online.

## introduction nonsuicidal self-injury (nssi), or the intentional injuring of one's body without aiming to die for reasons outside of social norms, causes significant morbidity @xcite . lifetime prevalence of nssi is estimated to range from 5-6% among adults to 17-18% among adolescents @xcite while the prevalence of nssi among adolescents with psychiatric disorders is thought to be much higher @xcite . qualitative, quantitative, mixed-methods, and psychometric studies have pointed towards the addictive features of nssi and shared characteristics between nssi and substance use disorders (suds; @xcite . populations who self-injure may resemble populations with suds in personality @xcite or impulsivity traits @xcite . nssi and sud are often comorbid with anxiety, depressive, and psychotic disorders @xcite and with each other, with one study reporting that approximately 60% of people who self-injure met criteria for a sud @xcite . both substance use and nssi are used to avoid and/or cope with feelings of psychological distress @xcite , especially among adolescents @xcite . although there is debate as to whether or not nssi is an addiction in a clinical sense or experienced as intensely as sud @xcite , addiction models of nssi have been proposed @xcite @xcite . there is also evidence that those who endorse more addictive features of self-injury harm themselves more frequently and more severely @xcite , have higher levels of internalized anger @xcite , and are at increased risk for accidentally harming to a greater extend than intended @xcite and attempting suicide @xcite . some have urged clinicians to consider addictive features of nssi when treating people who self-injure @xcite , making the addictive aspects of nssi a valuable research target. previous work has also identified the adoption of language used in sud recovery circles alcoholics anonymous (aa) and narcotics anonymous (na) in nssi communities. this "addiction language" (i.e., phrases such as "relapse", "recovery" and celebration of time without self-injury) has been found on nssi message boards @xcite , facebook groups (niwa and mandrusiak, 2012), and livejournal @xcite . this study builds on the work of @xcite , who investigated the use of "addiction language" and experiences of addiction in the r/selfharm subreddit. this was done through a text-based annotation process where experts in addiction and recovery adapted the diagnostic and statistical manual of mental disorders fifth edition (dsm-5) criteria for sud to nssi as a method for measuring the symptoms and severity of addiction to nssi for reddit users. results showed that over three-quarters of the sample met the criteria for addiction and 86% used "addiction language".this work also builds on a large body of research using reddit as a tool for mental health applications @xcite , which includes depression @xcite , anxiety (shen and rudzicz, 2017), suicide @xcite , substance use @xcite , schizophrenia @xcite , and dsm-5 evaluations @xcite . the purpose of this study is to further evaluate experiences of addiction by examining shared "addiction language" between nssi and sud communities using automated methods. we begin by directly comparing nssi and sud subreddits through a set of lda topics estimated over a corpus of reddit comments and examine how themes of addiction and recovery are used across both communities. while previous studies have identified "addiction language" in nssi communities, to our knowledge, none have directly compared nssi and sud communities. we also identify where users of these subreddits are posting across reddit in order to identify common communities. we end by discussing the clinical implications of our findings. ## results task 1: shared language in figure 1 shows the average user-level topic usage across all 50 topics, ordered by the difference between the nssi (green) and sud (blue) groups. in total, we see 9 out of 50 topics include addiction or recovery-related keywords within the top 10 highest weighted words in the topic. we do not include topics that contain both "clean" and "cut" since "clean" most likely does not refer to "staying clean" in the recovery sense. additionally, we see that the most similar topic is addiction-related ("addiction", "addicted"), as well as the 6th ("recovery", "relapsed", "clean"). notably, the remaining addiction topics are the least similar (i.e., towards the there are also a number of topics that do not contain recovery keywords but seem to be related to addiction and recovery such as mentions of starting/stopping ("started", "stop") and getting easier ("gets", "easier"). while not addiction or recovery related, we do see shared language of gratitude ("thanks" and "thank"), support ("better", "easier", "gets" as well as "support", "advice"), emotions ("thoughts", "feelings", "emotions"), and coping. task 3: posting activity ## conclusion in this work, we directly compared language across large online communities dedicated to discussing nssi and sud recovery. we showed that there is indeed a shared language of addiction between these two communities, evidenced by equivalent usage of topics related to addiction ("addiction", "addicted") and recovery ("recovery", "relapsed", "clean"). to our knowledge, this is the first study using automated methods to quantify addiction language in nssi communities, as well as the first to directly compare language between online nssi and sud recovery forums. we also examined reddit-wide posting activity and showed that, while nssi redditors posted in a number of mental health related subreddits, sud redditors did not even though both nssi and sud are comorbid with many of the same mental health disorders. one limitation of our study is the high comorbidity between nssi and sud: 60% of adolescents engaging in nssi meeting criteria for suds @xcite . thus, the shared addiction language may be a result of nssi redditors also having and discussing suds. we attempted to control for this by excluding redditors who are posting in both nssi and sud subreddits. additionally, @xcite noted that only 2% of nssi redditors explicitly mentioned having a sud. despite this limitation, our results suggest that the adoption of addiction and recovery language in nssi communities may provide psychological benefit to the users and help them cope with selfinjury. @xcite posits that alignment with sud may buffer against self-stigma and encourage adoption of common sud recovery strategies. in a similar study, @xcite suggest that people who self-injure use addiction messages to convey the difficulty in stopping, as well as to caution those considering nssi as a coping strategy. our results also suggest that nssi redditors seek support in similar communities for other mental health concerns, perhaps with the goals of broadening their support network or seeking specific advice for a separate mental disorder. the lack of mental health cross posting among sud redditors may imply a need for more discussion of cormorbid mental disorders among sud recovery communities as well as greater engagement with people dealing with other mental disorders. regardless, nssi and sud recovery communities share similar language of support ("yourself", "take", "care", "love") and encouragement ("better", "easier", "gets"), illustrating the broad psychological benefits of sharing intimate experiences with empathetic others online, regardless of the particular mental health concern.