Youth Experience Tracker Instrument: A self-report measure of developmental antecedents to severe mental illness

Aim: We sought to examine the structure, internal consistency, convergent and criterion validity of the Youth Experience Tracker Instrument (YETI), a new brief self-report measure designed to facilitate early identification of risk for severe forms of mental illness, including major depressive disorder, bipolar disorder, and schizophrenia. Methods: We collected 716 YETIs from 315 individuals aged 8 to 27 with and without familial risk of severe mental illness. The YETI measures six developmental antecedents that precede and predict serious forms of mental illness: affective lability, anxiety, basic symptoms, depressive symptoms, psychotic-like experiences, and sleep. A battery of concurrent questionnaires and interviews measured the same constructs. Results: The best-fitting bifactor model supported the validity of both total score and antecedent-specific subscales. Internal consistency was high for the total score (ω = 0.94) and subscales (ω = 0.80-0.92; ρ = 0.72). The total score captured the majority of information from the 26 YETI items (hierarchical omega ω_h = 0.74). Correlations of YETI subscales with established measures of the same constructs (r = 0.45-0.80) suggested adequate convergent validity. We propose cut-offs with high negative predictive values to facilitate efficient risk screening. Conclusion: The YETI, a brief self-report measure of antecedents, provides an alternative to using multiple longer instruments. Future research may examine the predictive validity of the YETI for the onset of major mood and psychotic disorders.