# Borderline personality disorder symptoms moderate the effect of risk-legitimizing beliefs on risky motorcycle riding among Thai university students

## TL;DR

This study shows that borderline personality disorder symptoms can increase risky motorcycle riding when combined with beliefs that justify such risks, especially among Thai university students.

## Contribution

The study reveals that BPD symptoms moderate the effect of risk-legitimizing beliefs on risky motorcycle riding behavior.

## Key findings

- BPD symptoms and risk-legitimizing beliefs independently predict risky motorcycle riding.
- The interaction between BPD symptoms and risk-legitimizing beliefs significantly increases risky riding behavior.
- The model explains 38.1% of the variance in risky riding behavior.

## Abstract

Motorcycle crashes remain a significant public health concern in Thailand, particularly among young adults who frequently engage in risky riding. Cognitive justifications—termed risk-legitimizing beliefs (RLBs)—may normalize unsafe behaviors, whereas borderline personality disorder (BPD) symptoms could intensify such tendencies. This study examined whether BPD symptoms moderate the association between RLBs and risky motorcycle riding.

A cross-sectional online survey was conducted among 247 university student motorcyclists in Northern Thailand. Participants completed validated Thai versions of the Motorcycle Rider Behavior Questionnaire (MRBQ), a 13-item RLBs scale, and the Screening Instrument for Borderline Personality Disorder (SI-Bord).

Approximately 23.5% of the participants scored above the SI-Bord cut-off (>7), indicating that clinically relevant BPD symptoms were relatively common in this sample. Hierarchical regression analyses tested whether BPD symptoms moderate the association between RLBs and risky riding, adjusting for demographic and behavioral covariates. Both RLBs (β = 0.246, p < 0.001) and BPD symptoms (β = 0.293, p < 0.001) independently predicted higher risky riding, and their interaction was significant (β = 0.212, p < 0.001). The complete model explained 38.1% of the variance.

Cognitive rationalizations and personality vulnerability jointly contribute to unsafe motorcycle riding. Preventive efforts should identify riders with elevated BPD symptoms and combine belief modification, emotion-regulation training, and peer-norm interventions to reduce motorcycle-related risks among young adults, especially in low- and middle-income settings.