Abstract

Substance use disorder (SUD) is a global public health crisis, with Northeast India exhibiting disproportionately high prevalence rates. Traditional socio-ecological models often emphasize familial and environmental factors in SUD etiology. This cross-sectional study investigated the interplay between self-reported triggers, family history, and pathological personality traits among N=62 male residents across three rehabilitation facilities in Jorhat, Assam. Utilizing the Personality Inventory for DSM-5 Brief Form (PID-5-BF), findings revealed that Disinhibition and Antagonism are the primary neuro-behavioral drivers of early onset, severe polysubstance use, and opioid endorsement. Contrary to socio-ecological assumptions, familial indicators (parental education and substance use) did not independently predict severity. However, a significant diathesis-stress interaction emerged: parental substance use exacerbated polysubstance severity exclusively among highly disinhibited individuals. Furthermore, comorbid gambling strongly aligned with intrapsychic triggers and a psychopathy-spectrum profile (high Detachment/Antagonism, low Negative Affect), indicating under-stimulation rather than distress. These results highlight the necessity of personality-targeted interventions, demonstrating that systemic family vulnerabilities catalyze severe SUD primarily in the presence of underlying personality pathology.