The present study introduces and validates the Self-Identity Lifelessness Scale (SILS), a novel instrument designed to measure a unique form of identity disturbance termed the Lifeless Self Syndrome. This syndrome is conceptualized as a chronic condition characterized by emotional lifelessness, identity diffusion, and internalized guilt, hypothesized to emerge from symbolic role substitution following early familial loss - particularly the death of a sibling. Based on theoretical modeling, psychobiographical analysis, and qualitative input from five focus groups (N = 278), a 30-item scale was developed and psychometrically tested.

Exploratory factor analysis revealed a four-factor structure - (1) Emotional Derealization and Loss of Authentic Self, (2) Identification Splitting and Substitutive Existence, (3) Dependent Self and Relational Insecurity, and (4) Introjected Guilt and Compensatory Identity—explaining 59.73% of the variance. The scale demonstrated strong internal consistency and construct coherence.

Nonparametric tests were conducted due to non-normal distribution. Mann–Whitney U tests showed significantly higher SILS scores among individuals born after a deceased sibling, particularly on dissociation and guilt-related subscales (p < .05). Kruskal–Wallis analyses further confirmed that sibling loss in conscious life is associated with the highest levels of identity disturbance across all factors. The findings provide initial empirical support for the Lifeless Self construct and underscore the psychological impact of early symbolic loss. The SILS offers a promising tool for identifying individuals at risk of deep-seated identity pathology linked to unresolved mourning and familial role imposition.