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OBJECTIVE: Describe the development and psychometric validation of a brief scale (the Sleep Condition Indicator (SCI)) to evaluate insomnia disorder in everyday clinical practice. DESIGN: The SCI was evaluated across five study samples. Content validity, internal consistency and concurrent validity were investigated. PARTICIPANTS: 30 941 individuals (71% female) completed the SCI along with other descriptive demographic and clinical information. SETTING: Data acquired on dedicated websites. RESULTS: The eight-item SCI (concerns about getting to sleep, remaining asleep, sleep quality, daytime personal functioning, daytime performance, duration of sleep problem, nights per week having a sleep problem and extent troubled by poor sleep) had robust internal consistency (α≥0.86) and showed convergent validity with the Pittsburgh Sleep Quality Index and Insomnia Severity Index. A two-item short-form (SCI-02: nights per week having a sleep problem, extent troubled by poor sleep), derived using linear regression modelling, correlated strongly with the SCI total score (r=0.90). CONCLUSIONS: The SCI has potential as a clinical screening tool for appraising insomnia symptoms against Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) criteria.

Original publication




Journal article


BMJ Open

Publication Date





Psychiatry, Sleep Medicine, Adult, Female, Humans, Linear Models, Male, Middle Aged, Psychometrics, Reproducibility of Results, Severity of Illness Index, Sleep, Sleep Initiation and Maintenance Disorders, Sleep Wake Disorders, Surveys and Questionnaires, Young Adult