Longitudinal Clinical and Functional Outcomes in Adult-Onset Delusional Disorder and Schizophrenia: A 10-Year Prospective Comparison Study
Year: 2026
Type: article
Study design: Observational Study
Abstract: BACKGROUND AND HYPOTHESIS: The distinction between delusional disorder (DD) and schizophrenia (SZ) remains debated, and onset age is an often-overlooked prognostic factor. We hypothesized that SZ would show greater diagnostic stability than DD, while functional and cognitive outcomes would be broadly comparable, with clinical differences emerging over time. STUDY DESIGN: Diagnostic stability over a decade was examined in an age-matched first-episode DD and SZ cohort (n = 142). 10-year clinical, functional, and cognitive outcomes were then compared among participants who retained their original diagnosis throughout follow-up (n = 111). Missing data were addressed using multiple imputation, with sensitivity analyses conducted in complete cases (n = 82) and deceased-excluded cases (n = 100). STUDY RESULTS: Over 10 years, 41% (29/71) of participants initially diagnosed with DD transitioned to SZ, compared with 3% (2/71) of those initially diagnosed with SZ who experienced a diagnostic shift. Among participants who retained their original diagnosis throughout follow-up (n = 111), SZ was associated with more relapses (B = 1.27, P = .012), hospitalizations (B = 0.47, P = .050), hallucinations (B = 3.35, P = .012), and perseverative errors on the modified Wisconsin Card Sorting Test (B = 4.31, P = .040), whereas DD showed poorer insight (Scale to Assess Unawareness of Mental Disorder: B = -1.38, P = .002). Sensitivity analyses yielded consistent results. CONCLUSION: These findings support a psychosis-spectrum model in which stable DD and SZ show substantial longitudinal overlap in functioning and cognition, despite differences in diagnostic stability and selected clinical outcomes.
Source: Schizophrenia Bulletin
Authors: Christy Lai Ming Hui, Charlie Cheuk Lam Wong, Nicole Cai Lin Yang, Evie Wai Ting Chan, Yi Nam Suen, Edwin Ho Ming Lee, Sherry Kit Wa Chan, Wing Chung Chang, Charles Wai Hong Chan, Wai Song Yeung, Man Wah Siu, Eric Wai Ching Yan, Lap Tak Poon, Pui Fai Pang, Alison Wai Fan Lo, Wing King Lee, Mindi Wing Yan Chiu, Jenny Pik Ho Lam, Simon Sai Yu Lui, Yip Chau Wong, Eric Yu Hai Chen
Language: English
Subfield: Psychiatry and Mental health
Field: Medicine
Domain: Health Sciences
Open Access status: green
Funder: Health and Medical Research Fund
OpenAlex ID: W7224112771