In adolescents, a previous suicide attempt (SA) is associated with its recurrence1,2). Among self-harms in adults, drug intoxication (DI) as the method at initial SA is associated with a 2.5-5-fold decrease in recurrent attempts compared to hanging3,4). However, switching to more lethal methods is a predictor of completed suicide in adults (adjusted hazard ratio, 7.05)5). In patients aged 10-24 years with DI, those aged 10-17 years have a 1.3-fold higher risk of repeated self-harm than those aged 18-24 years6). Despite the lower severity of suicidal intention and the overuse of over-the-counter medicine in adolescents7), their higher rate of repetition of SAs may lead to fatal outcomes. There is a scarcity of studies focusing on the completed suicide rate with severity in adolescents, beyond the rate of recurrence.

From this viewpoint, we focused on index methods of SAs, defined as the methods used at initial SAs, to investigate factors predicting the outcome of SAs among adolescents in emergency settings.

Among 364 adolescents with possible suicidal idea or attempt, 227 were selected as the study population (Fig. 1). The meaningful SAs (80 [35.2%]) comprised 71 hospitalizations, 8 deaths, and 1 transfer.

Table 1 lists the characteristics of the study population according to the meaningful SAs. Among the index methods, cutting was most common (50.7%). The adolescents with meaningful SA chose DI, fall, and hanging as the index methods more frequently than those without meaningful SA (P < 0.001). Multiple (i.e., recurrent) SAs were reported by 118 adolescents (52.0%) with a lower frequency in those with meaningful SA (57.1% vs. 42.5%; P = 0.038). Of the 118 adolescents, 72 changed the methods once and 14 twice or more.

The regression analysis showed that sex, age group, psychiatric history, and the number of changes in the methods of SAs had no significant associations with the meaningful SAs (Table 2). The adjusted odds ratio of fall as the index method was 6.93 (95% confidence interval, 1.70-28.26; compared with those with DI) whereas the adjusted odds ratio of cutting was 0.39 (0.17-0.91; compared with the same reference). In addition, multiple SAs were associated with the meaningful SA (1.76 [1.04-3.13]).

Of the 80 adolescents with meaningful SAs, 46 (57.5%) obtained the outcomes at the first attempt whereas the remaining 34 (42.5%) did in 2 or more attempts. The former group tended to choose DI (29/46) as the index method whereas the latter mostly chose cutting (30/34). Among the 30 adolescents who chose cutting, only 8 did as the final method, which led to the meaningful SA. The other 22 adolescents chose the following final methods; 12 DIs, 3 fallings, 3 hangings, and 4 others. Adolescents who chose falling or hanging as the index methods did not experience multiple SAs.

This study shows the independent association of the index methods of SAs with the outcomes. Compared to DI as the index method, fall and cutting were associated more strongly and weakly, respectively, with the meaningful SA, suggesting that the more fatal the method, the more fatal the outcome (Table 2). Furthermore, the adolescents who chose cutting tended to change their final methods of SAs to more fatal ones, such as DI, in their subsequent attempts, rather than to repeat the cutting (see the last paragraph in Results), though the difference was not significant. This finding suggests a potential association between repetition of SAs and changes to more fatal methods. In addition, multiple SAs were associated with the outcomes despite the non-significant association of the number of changes in the methods of SAs with the meaningful SA (Table 2). With more studies on the abovementioned potential association, changing methods may be a factor for SA-related outcomes in EDs.

We defined the meaningful SAs in a broader fashion unlike previous studies focusing on an individual death3). This broader definition was intended to provide care for adolescents with SA before the occurrence of the completed suicide.

An adult study showed that hanging, drowning or jumping as the index methods had stronger associations with the eventually completed suicide than DI, while cutting or piercing showed a similar degree of association with the outcome using the same reference8). In that study, 60.9% of the adults who chose DI and 15.8% of those who did cutting or piercing used the same methods at the eventual completed suicide8). Clearly, fatal methods result in greater lethality than non-fatal methods9,10). These studies support our finding that cutting had a weaker association with the meaningful SA than DI.

This study has several limitations. First, the adolescents’ psychiatric histories could vary when the histories were based solely on their memories, suggesting a possibility of missing or incorrect data. Second, the data were collected in a single center where the adolescents who were on the psychiatric follow-up could be hospitalized more readily, regardless of their severity. Third, we did not include long-term outcomes as in several previous studies6,11,12).

This study identifies predictors of the meaningful SAs, including the index methods and multiple SAs, in adolescents who visited the ED. Therefore, information on the index methods should be obtained from adolescents with SAs in EDs. In adolescents with multiple SAs, changes in the methods of SAs may be additionally considered.