Importance: Standardized diagnostic interviews (SDIs) are structured assessments based on established criteria to improve the consistency and reliability of diagnoses. The pooled test-retest reliability of SDIs for adult psychiatric disorders is unknown.

Question: What is the pooled test-retest reliability of standardized diagnostic interviews for common adult psychiatric disorders, including groups of mental disorders and substance use disorders (SUDs), and which factors explain between-study variation?

Findings: In this systematic review and meta-analysis of 57 studies, the overall test-retest reliability of standardized diagnostic interviews was moderate and highly heterogeneous, with significantly higher reliability for SUDs than for mental disorders. Only diagnostic criteria partially explained between-study variation in SUDs.

Meaning: The finding that standardized diagnostic interviews, although regarded as the gold standard of psychiatric disorder classification, had moderate and highly variable test-retest reliability highlights the need for careful selection and use.