Drug Discov Ther. 2026;20(3):235-244. (DOI: 10.5582/ddt.2026.01019)

Seasonality of psychiatric symptoms in older adults in long-term psychiatric care

Tomoki K, Yuma S

The annual periodicity of psychiatric symptoms in older adults within long-term care remains under-explored. This exploratory, single-center, retrospective pilot study investigated seasonality in agitation/aggression, depressive symptoms, and hallucinations/delusions among 28 older Japanese inpatients (mean age 74.1 ± 9.1 years) over a one-year period to inform the chronobiological optimization of pharmacotherapy. Generalized Linear Mixed-effects Models (GLMMs) with trigonometric terms were used to assess periodicity based on daily clinical records. A possible seasonal pattern, with the model-estimated peak in March and nadir in September, was observed for agitation/aggression (Incidence Rate Ratio [IRR] = 1.50, p = 0.037) and depressive symptoms (IRR = 1.08, p = 0.041). Hallucinations/delusions showed no significant periodicity. These findings suggest that older adults in long-term care retain sensitivity to seasonal environmental changes, with spring representing a potential period of circadian vulnerability. These findings may help identify periods requiring closer clinical monitoring and medication review, although prospective studies are needed before seasonally guided dosage adjustments can be recommended.

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