Little is known about Self-Injurious Thoughts & Behaviors and Non-Suicidal Self-Injury in firefighters in two East Coast United States metropolitan fire departments based on fire service tenure.

• Study comprised of two parts, a survey and a questionnaire, both conducted online. Using the Computer Adaptive Test–Suicide Scale

• The only computer-based adaptive mental and behavioral health assessment clinically validated worldwide.

• Validated against face-to-face structured clinician-led assessment.

• Participants received a unique identifier and hyperlink allowing them access and confidentiality.

• Study was completed on participants' personal electronic devices, on their own time, at their own pace.

A single-factor or One-Way ANOVA tested for a significant relationship between the variables and the four tenure groups simultaneously. Time of administration averaged 86 seconds, with a median of eleven questions.

The C-SSRS identified six participants triggering suicide alerts. One in the early-career category and five in the late-career category. The CAT-SS identified one participant as high-risk and 33 participants for suicidality. One participant in the early-career category.

Early-career and late-career firefighters have more self-injurious thoughts and behaviors and mid-career firefighters have the least.