Suicide prevention is critical in regions with high suicide mortality rates, such as Akita Prefecture, Japan, requiring effective tools for identifying suicidal ideation. The 15-item Interpersonal Needs Questionnaire (INQ-15) measures perceived burdensomeness (PB) and thwarted belongingness (TB). The statistically derived cutoff scores for the Japanese version (INQ-15J) remain unexamined. To determine cutoff scores for the INQ-15J to identify individuals with suicidal ideation and evaluate screening accuracy based on population data. A total of 1,650 residents aged 20–79 years (response rate: 33.0%) completed the INQ-15J. Receiver operating characteristic analyses identified cutoff scores for PB and TB for suicidal ideation in the past month and lifetime. Multiple logistic regression assessed the independent associations of PB and TB with suicidal ideation. Screening performance was further examined using parallel (high-PB or high-TB) and serial (high-PB and high-TB) applications. The statistically derived cutoff scores (PB = 21; TB = 34) showed moderate accuracy for identifying suicidal ideation in the past month. PB and TB were independently associated with suicidal ideation. The parallel application increased sensitivity, whereas the serial application increased specificity. The INQ-15J offers a practical, indirect approach for identifying individuals with suicidal ideation in community settings. Combining PB and TB cutoff scores allows flexibility depending on whether sensitivity or specificity is prioritized. Further validation in diverse populations is warranted. Not applicable.
Miyamoto et al. (Sat,) studied this question.