Pineal Gland Volume, Sleep Quality, and Psychiatric Disorders: A Systematic Review and Meta-Analysis
Abstract
Introduction: Disturbances in sleep and circadian rhythms are features of several psychiatric disorders. The pineal gland regulates these rhythms via melatonin, with pineal gland volume (PGV) serving as a structural proxy. We conducted a meta-analysis to synthesize evidence on differences in PGV between patients with psychiatric disorders and healthy controls and the association between PGV and sleep outcomes.
Method: Systematic searches of PubMed, Embase, Scopus, and Web of Science were performed (August 2025). Study quality was assessed using the Newcastle-Ottawa Scale. Random-effects meta-analyses using restricted maximum likelihood (REML) estimation were conducted for correlation and group-comparison outcomes. Subgroup analyses were performed by diagnostic category.
Results: Fourteen studies compared PGV between psychiatric patients and healthy controls, and seven studies examined associations between PGV and sleep outcomes. PGV was significantly lower in patients with psychiatric disorders compared with healthy controls (1055 patients, 712 controls, Hedges' g = -0.54 [-0.68, -0.41], p r = 0.18 [-0.08, 0.43], p = 0.136), with substantial heterogeneity (I2 = 82%), likely reflecting variability in sleep assessment and study populations.
Conclusion: Across psychiatric disorders, PGV is reduced relative to healthy controls, with the largest and most consistent reductions observed in schizophrenia spectrum disorders. In contrast, evidence for an association between PGV and…
How strong is the evidence?
Evidence Hub reads this as a meta-analysis, done in people. Its evidence level is 1 of 5 (Highest · pooled evidence). Pooled evidence from several studies sits at the top of the evidence pyramid. Reported size: 1,055 participants or records.
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