Nonsuicidal self-injury (NSSI), the direct and deliberate damage of one’s body tissue without suicidal intent (eg, cutting and hitting oneself), is a major mental health concern worldwide. Epidemiological surveys indicate that 1 in 5 individuals engage in NSSI before the age of 25 years [1-3], with 12-month rates in the 8% to 19% range [1,2] and many individuals reporting persistent NSSI for several years [4]. These rates are considerably higher among individuals seeking treatment [5-7], with more than half of adolescent inpatients and 1 in 10 emerging adult and adult outpatients reporting monthly NSSI [8,9]. Furthermore, the presence of NSSI predicts rehospitalization [10], is highly stigmatized [11], and is uniquely associated with an increased risk for psychiatric disorders [2,9,12-15] and suicidal thoughts and behaviors (STB). For instance, research shows that people who engage in NSSI are more likely to make a suicide attempt independent of mental disorders [16,17], with those engaging in repetitive persistent NSSI being most likely to attempt suicide and experience adverse psychosocial outcomes [18]. As such, there is an urgent need to better understand, predict, and prevent self-injury among people who frequently engage in these behaviors.

Unfortunately, we still lack basic knowledge of the descriptive nature of NSSI and how, why, and when self-injury unfolds in everyday life [19], a prerequisite for risk screening and intervention to prevent NSSI and clinically associated outcomes (eg, suicide attempts). This lack of progress is largely because most empirical studies have focused on establishing the prevalence and correlates of the presence and severity of NSSI using cross-sectional designs. Although longitudinal studies have been conducted, they typically used observation windows from months to years [19-21], providing a long-distance view of who is at greater risk of engaging in NSSI compared with others. However, such a nomothetic approach does not clarify when someone is at risk in the short term and in what daily life contexts they are more at risk and will thus not help clinicians to decide whether an individual is likely to self-injure within the next days and weeks. Making these decisions requires an idiographic approach and knowledge of the course, contexts of risk, and the relationship of NSSI with other self-damaging behaviors in daily life. Such information would be helpful for better informing mental health professionals and allocating treatment resources.

Similar to other frequently co-occurring self-damaging behaviors (eg, attempting suicide, binge eating, purging, and binge drinking) [2,13,22], NSSI cannot be ethically induced in the laboratory but occurs in people’s everyday lives. Although studying NSSI as it unfolds in real time has historically been challenging, recent technological advancements have made it possible to do exactly this, which has the potential to substantially improve our understanding and inform prevention efforts [19,23]. Ecological momentary assessment (EMA; also called experience sampling, ambulatory assessment, or real-time monitoring) involves prompting individuals multiple times per day via their mobile phone to provide in-the-moment information on social appraisals, emotions, cognitions, and behavioral patterns as they are lived in the flow of daily life [24-26]. Prior research suggests that NSSI thoughts can change substantially across hours [27], essentially necessitating EMA to (1) capture these real-time changes and (2) enable the identification of factors that predict these changes in daily life.

Advancing insight into the course and contexts of elevated risk for NSSI thoughts (ie, thinking about deliberately hurting oneself), NSSI urges (ie, a difficult-to-control desire to self-injure), self-efficacy to resist NSSI (ie, confidence in one’s ability not to engage in self-injury), and NSSI behavior (ie, engagement in self-injury) would uniquely inform researchers and clinicians about how self-injury unfolds and is experienced by those at highest risk. This in-the-moment information can transform our ability to prevent and manage NSSI among individuals seeking treatment by providing the scientific building blocks for novel digital interventions that support people who self-injure in real time [19,28,29]. The DAILY (Detection of Acute rIsk of seLf-injurY) project aims to address these gaps using a 28-day EMA protocol among individuals seeking treatment. This protocol paper presents the project’s aims, design, and materials used. Figure 1 provides a graphical presentation of the primary objectives of the DAILY project.

The first primary objective is to clarify the short-term course and within-person predictors of NSSI. Initial work among community samples suggests that NSSI thoughts are usually short-lived and moderate in intensity [30-32], with a higher risk of more intense and persistent NSSI thoughts toward the evening [32] and an average of 1.6 (SD 1.1) NSSI behaviors per week [30]. Surprisingly, however, the short-term clinical course of NSSI remains to be comprehensively investigated among individuals seeking treatment. The intensive nature of the longitudinal data we collect will allow for a detailed picture of the thought and behavioral patterns and help us to address several critical unanswered questions about the course of NSSI among individuals seeking treatment: how much do NSSI thoughts, NSSI urges, self-efficacy to resist NSSI, and NSSI behavior (1) vary between people seeking treatment, (2) vary within people seeking treatment, (3) vary throughout the day and the week, and (4) covary and predict each other prospectively in daily life?

Guided by contemporaneous models of NSSI [33-35] and emerging work [36-38], we will evaluate contextual information, social appraisals, emotions, and cognitions as within-person risk and protective factors for cognitive and behavioral NSSI outcomes. We hypothesize that the risk of NSSI behavior will be higher when people are alone [30], after situations characterized by negative social appraisals and perceived conflict [39,40], and after increased negative and decreased positive affect [41]. Given that specific emotions may incrementally predict higher risk (eg, feeling stressed) [30,42] or protect more strongly against NSSI (eg, feeling relaxed) [27], the findings will also be analyzed using specific emotions as units of analysis. On the basis of the benefits and barriers model of NSSI [34,43], which argues for a unique role of self-critical thoughts in explaining NSSI behavior, we will evaluate the association between momentary fluctuations in self-critical thinking and NSSI urges and NSSI behavior. Building upon the emotional cascade model [35,44], which posits that reinforcing cyclic cascades between rumination and negative affect form a dynamic process in which self-injury is suggested to break this cycle by distracting from rumination, the utility of momentary ruminative thinking and the interplay with negative emotions in predicting NSSI behavior will be investigated. However, because the relevance of these theoretically inspired within-person risk factors for NSSI might differ between individuals [45,46], we will also determine variability in individual risk associations.

A second primary objective is to advance understanding of the transition from NSSI thoughts and urges to NSSI behavior. Although existing theoretical models of NSSI do not distinguish between NSSI thoughts or urges and NSSI behavior, contemporary “ideation-to-action” theories of suicide explicitly make this distinction [47] and suggest that the factors that lead to suicidal thoughts or urges are not necessarily the same factors that lead to behavior (ie, suicide attempts). Emerging evidence indicates that incorporating ideation-to-action thinking might be equally relevant for NSSI. For instance, preliminary work suggests that previously identified risk factors for NSSI behavior (eg, emotional factors) might uniquely predict NSSI thoughts but not the occurrence of NSSI behavior [27]. Inspired by the cognitive-emotional model of NSSI [33], we anticipate that momentary self-efficacy to resist NSSI will be a potent protective factor against NSSI behavior. People retrospectively report that the transition between NSSI thoughts or urges and NSSI behavior is typically <30 minutes [30,31], meaning that there might be a brief window of opportunity to intervene during these moments of acute risk for NSSI behavior. Therefore, in an attempt to inform and facilitate such intervention efforts, we will make a thought-to-action distinction and clarify the specificity of risk and protective factors to identify factors that increase or decrease the likelihood of transitioning from NSSI thoughts or urges to NSSI behavior in real time among individuals seeking treatment.

A third primary objective is to provide novel data on the co-occurrence of NSSI with other self-damaging behaviors in daily life that may represent different forms of behavior that serve the same function (ie, disordered eating, substance use, and STB) [13,30,48-51]. For example, previous daily diary studies found that 42% to 53% of the adolescents and emerging adults who engage in NSSI reported at least 1 episode of disordered eating and suicidal ideation [40,52], with suicidal thoughts being present on most days when adolescents engaged in NSSI [53]. Similarly, Nock et al [30] observed that NSSI thoughts co-occurred 13% to 18% of the time with thoughts of substance use and disordered eating. Therefore, disordered eating (ie, restrictive eating, binge eating, and purging), substance use (ie, binge drinking and smoking cannabis), and STB will be assessed as secondary outcomes. From a transdiagnostic approach, this will help to clarify comorbidity patterns, unique versus shared risk factors, and temporal relationships with other self-damaging behaviors in daily life [13,19,54]. In addition, it will allow us to address whether the dynamic characteristics of NSSI thoughts or urges (ie, an individual’s within-person average and variability) and frequency of NSSI behavior—as observed in the EMA—predict changes in NSSI trajectories and the presence of comorbid self-damaging behaviors among individuals seeking treatment [55]. For instance, it may be that persistently high NSSI urges and frequent NSSI behavior increase the risk of STB [53]. Alternatively, there could also be a behavior shift such that a reduced frequency of NSSI leads some individuals to take up another behavior that serves a similar function.

Finally, a secondary aim is to evaluate the perspectives of individuals seeking treatment and mental health professionals regarding the feasibility, scope, and utility of digital self-monitoring and novel interventions. There is a growing awareness that the clinical implementation of EMA and ecological momentary interventions (EMIs), which use EMA to deliver support in real-time, provides new opportunities to make individuals more actively involved in their treatment and to better match treatments to their needs [19,24,56,57]. For instance, EMA could facilitate self-insight about relevant processes [19,58,59], whereas EMIs would allow for providing support outside of the therapy room in daily life. Initial findings indicate the acceptability and potential of EMIs for NSSI and suicide prevention [29,60,61], but, despite the clear clinical potential, this remains a largely underexplored area. Importantly, however, the development of EMIs will advance more rapidly and be more easily clinically implemented when a user-centered design is employed. Such a design actively involves and acknowledges end users from the initial stage of development to understand the goals, challenges, and motivations for future EMIs that seek to facilitate young people’s recovery from self-injury and other self-damaging behaviors [62].

To investigate the objectives of the DAILY project, the target population is adolescents (aged 15-18 years), emerging adults (aged 19-29 years), and adults (aged 30-39 years) seeking treatment and their mental health professionals. They are recruited from mental health services across the Flanders region of Belgium, including 9 inpatient services, 8 outpatient services, and 4 services with a hybrid care model. Of these services, 11 focus on emotion dysregulation and mood disorders, 5 focus on social-emotional difficulties in transitioning from adolescence to emerging adulthood, 3 focus on eating disorders, and 2 are private practices. Potential eligible participants are informed about the study via mental health professionals, study flyers, and information moments at these mental health services. The inclusion criteria for patients are as follows: (1) being aged between 15 and 39 years, (2) having sufficient Dutch-language proficiency, (3) past-month NSSI thoughts/behaviors, and (4) receiving inpatient or outpatient treatment. Individuals with cognitive deficits that preclude comprehension of materials are excluded from participation. Although adult participants (aged ≥18 years) could opt to continue participation when they decided to stop treatment, a treating mental health professional had to be involved for minors (<18 years) during the entire monitoring period, meaning that participation automatically ended when they interrupted their treatment before the end of the 28-day EMA protocol. The inclusion criterion for mental health professionals is being a licensed psychiatrist, clinical psychologist, or mental health nurse.

All phases of the DAILY project were approved by the Ethics Committee Research UZ/KU Leuven on February 10, 2021 (s64989 and B3222020000343), and all procedures align with the 1964 Helsinki declaration and its later amendments.

The DAILY project consists of 3 phases, including a baseline assessment (phase 1), 28 days of EMA followed by a clinical session and feedback survey (phase 2), and 2 follow-up surveys and an optional interview (phase 3). Figure 2 provides a graphical overview of the project.

The DAILY project is expected to advance scientific knowledge of (1) the short-term course and within-person risk and protective factors of NSSI thoughts, NSSI urges, self-efficacy to resist NSSI, and NSSI behavior among individuals seeking treatment; (2) the transition from NSSI thoughts and urges to NSSI behavior; and (3) the comorbidity patterns, unique versus shared risk factors, and temporal relationships of NSSI with other self-damaging behaviors. Such information will inform clinical practice about how, why, and when self-injury and other self-damaging behaviors unfold in the everyday lives of individuals seeking treatment. Building upon these findings, we will explore the experiences and perspectives of end users (ie, people with lived experience and their mental health professionals) about the feasibility, scope, and utility of EMA and EMIs as digital clinical tools in treatment. This will provide the scientific building blocks for novel intervention approaches outside of the therapy room to support individuals who self-injure in real time. For instance, a sophisticated EMI that shows promise for dynamic behaviors such as NSSI and STB is just-in-time adaptive interventions [29,138,139]. This highly innovative intervention design adapts the provision of support in terms of type, intensity, and timing to an individual’s changing status and context to facilitate real-time interventions when and where they are needed most in everyday life and in ways that are appropriate and evidence based [140].

Although EMA is a powerful methodology that can now more readily be used to provide previously unavailable information about the course, within-person predictors, comorbidity patterns, and clinical outcomes of NSSI in daily life [19], it is crucial to consider the implications and limitations of the protocol used and the design when interpreting the project’s findings. First, although measures are in place to ensure that recruitment is inclusive and geographically representative, with recruitment sites spread across the entire Flanders region of Belgium, it should be acknowledged that we use convenience sampling, with the targeted sample comprising individuals currently receiving mental health treatment. This implies that the findings should not be generalized to nonclinical populations because the short-term course of NSSI will likely differ in severity for community samples. Relatedly, adolescents can only participate from the age of 15 years, meaning that the findings are not generalizable to early adolescents (aged 10-14 years) and should be studied in this population. Second, the intensive sampling scheme matches the project’s research objectives but involves a higher burden than traditional longitudinal studies (typically 1-5 surveys months to years apart) and most EMA studies (typically lasting 1 week) [26]. Although scholars have observed increased burden with longer questionnaires but not with increased sampling frequency among community samples [141], it should be investigated to what extent the current EMA sampling scheme and duration were considered feasible by all individuals seeking treatment. Third, we implemented safety measures for NSSI and other self-damaging behaviors (including the monitoring of suicide risk) based on prespecified cutoffs of momentary urges and low self-efficacy to resist a behavior. Future research would benefit from evaluating risk thresholds and the utility of different safety measures (eg, personal vs standard message and human-led vs automatic action) at varying risk levels for self-damaging behaviors.

Fourth, we operationalize NSSI and other self-damaging behaviors comprehensively (ie, thoughts, urges, and behavior) and assess a broad range of theoretically relevant factors (emotions, cognitions, contextual information, and social appraisals); however, as a consequence, most constructs rely on single EMA items that were selected from prior EMA studies or modified from conventional survey questionnaires to keep the workload for participants under control [141]. However, against the backdrop of a lack of psychometrically validated items for assessing psychological constructs with EMA [142] and a need to develop standardized measures [143], we will calculate the multilevel reliability of composite constructs (eg, negative affect) and made all EMA items (for the original Dutch items see the OSF page) publicly available [107]. Fifth, we provided additional (shorter) EMA surveys when participants report intense NSSI urges and contact participants and clinical staff when there is an increased suicide risk, which might result in underreporting of NSSI urges and STB. Sixth, because all participants receive mental health treatment, there might be structural changes in the descriptive patterns of self-damaging thoughts and behaviors across the monitoring period. We will evaluate this, and if the assumption of stationarity is violated, we will include days since study enrollment as a covariate for the outcome under investigation. Finally, we may miss moments leading up to self-damaging behaviors in the late evening and overnight as no EMA surveys are scheduled after 10 PM. Although we can assess to what extent this is the case for NSSI behavior (as people could register self-injury via the push button in the m-Path app), future research might benefit from sampling schemes adapted to people’s sleep and wake-up times.

Notwithstanding the limitations, the findings of the DAILY project will provide a detailed characterization of the course and patterns of risk for NSSI during treatment by considering NSSI thoughts, NSSI urges, self-efficacy to resist NSSI, and NSSI behavior in the daily lives of individuals seeking treatment. This will help to increase our understanding of how NSSI unfolds across minutes, hours, days, and weeks. Filling these critical knowledge gaps using EMA will lay the foundation for, and guide, the development of novel interventions that support people when and where it matters most in daily life [29,138]. This scientific endeavor may facilitate young people’s recovery from self-injury and ultimately could help us prevent loss of life.