Our secondary analysis of data from the ACTION-J study on self-poisoning indicated that assertive case management significantly reduced the incidence of a first recurrent episode within 6 months after group assignment by approximately half. Furthermore, the number of overall self-harm episodes during the entire study period decreased by approximately 20% in the intervention group. Distribution analysis of the number of self-harm episodes indicated that the effectiveness of assertive case management on repeat self-harm could be attributed to a reduction in the number of patients with multiple repetitions (three or more episodes). We also evaluated the numbers of repeat suicide attempts and non-suicidal self-harm episodes as additional outcomes, and found that the intervention led to a greater reduction of non-suicidal self-harm episodes than suicide attempts. These findings indicate that assertive case management is an effective intervention for self-poisoning as an act of self-harm, irrespective of levels of suicidal intent. Compared with previous reports, these data indicate clearer patterns regarding the effectiveness of assertive case management [13, 14].
Several randomized controlled trials have used a case management approach to implement interventions following suicide attempts [16, 17]. Our data indicate that active contact and follow-up interventions as components of assertive case management programs significantly reduced the proportion of recurrent suicide attempts within 6 months after group assignment by approximately half. However, evidence regarding the effectiveness of interventions in reducing the proportion of recurrent suicide attempts and the number of repeat self-harm episodes is still very limited [17]. Assertive case management used in the present study comprised a comprehensive intervention package. The entire intervention package is needed, as several previous studies using partial interventions have failed to show any effectiveness, and any one element of the intervention probably would be no more effective than the other elements. This assertive case management program appears to have an important effect on the engagement of suicidal patients in continuous treatment and care. Further studies will be needed to determine whether the intervention is effective in other settings and regions.
Our study has several strengths. First, this is a secondary analysis of a large randomized controlled multicentre study. Baseline characteristics were well balanced between the intervention and control groups, and also between subgroups (i.e., individuals who engaged in self-poisoning). Second, the trial was conducted in a pragmatic and real-world setting, and high adherence to the intervention was achieved. Third, unlike some previous studies that excluded individuals with certain mental disorders or certain levels of severity, our study included patients with a broad range of mental disorders, as shown in Table 2. Fourth, the primary outcome in this analysis was the incidence of a first recurrent suicide attempt within 6 months after group assignment and the secondary outcomes were the number of overall self-harm episodes per person-year. This enabled us to estimate the effect of the intervention on the overall burden of suicidal behaviour. The number of overall self-harm episodes per person-year is a common outcome among interventional studies of suicide attempts and self-harm, and may be more useful for comparison with other studies than first recurrent suicide attempts, which was also used as the primary outcome in the ACTION-J study [13].
Our focus only on participants who poisoned themselves differentiates our study from previous reports [13, 14]. The studies by Kawanishi et al. and Furuno et al. used suicidal behaviour data from the complete ACTION-J study, which included all methods of attempted suicide. Self-poisoning is frequently seen in suicide attempters, and, together with self-cutting, is one of the most common methods of self-harm. The method of self-poisoning often includes an addictive element as one of its pathological features, and so self-poisoning may be a very strong predictor of subsequent suicide attempts [18]. Therefore, interventions for self-poisoning and repeated self-poisoning are pivotal in suicide prevention [19]. Previous intervention studies of self-poisoning patients differed in terms of patient background and methodology, resulting in different outcomes [6–11]. Therefore, an intervention for self-poisoning patients based on clear patient background information and a solid study design was needed. For these reasons, we chose to examine the preventive effects of interventions for self-poisoning participants from the ACTION-J study. We also aimed to compare data from self-poisoning patients from the ACTION-J study with data from participants of these previous studies.
The ACTION-J study included only suicide attempters with apparent suicidal intent who were registered after admission to the emergency department for attempted suicide. This approach was taken to increase the feasibility of the intervention study. However, it is not easy to implement an intervention study that incorporates individuals who self-harm, attempt suicide, or have suicidal ideation, given their complicated backgrounds [20]. To implement the intervention consistently, participants from a specific background should be selected. It remains unclear whether the present results are valid for attempted suicide without suicidal intent. This is a topic for a future study.
Our study also has several limitations. First, we excluded patients younger than 20 years for ethical reasons. However, self-harm is common and highly recurrent in adolescents [21]. Patients who engaged in self-harm but were not admitted to an emergency department were also excluded from our study. In view of these exclusion criteria, the study population may differ somewhat from the general population of patients who engage in self-harm and are admitted to emergency departments, as well as from the populations assessed in some previous studies. Second, we excluded participants who did not meet the criteria for suicidal intent. As we adopted relatively stringent criteria for suicidal intent, we may have excluded participants who potentially would have been eligible to participate in other studies relating to suicidal behaviour. This difference in criteria may affect the comparability of our study with others. Third, differences in existing medical resources or social support between countries may influence the effect of interventions. This should be taken into account when similar interventions are implemented outside Japan.