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Bipolar disorder is associated with increased cerebrospinal fluid and intracranial volumes compared to controlsBrain structure differences found in people with bipolar disorder

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Key Takeaway
Note that Bipolar Disorder is associated with significantly greater CSF and intracranial volumes compared to controls.

This meta-analysis examines brain regional volumetric alterations in adults with Bipolar Disorder (DSM-IV to DSM-5-TR criteria). The study synthesizes data regarding intracranial structures to identify consistent patterns in the patient population compared to healthy controls.

Key findings indicate that individuals with Bipolar Disorder have significantly greater cerebrospinal fluid (CSF) volume, intracranial volume, and right lateral ventricle volume than controls. Additionally, the analysis found significantly greater variability in both CSF and intracranial volumes among individuals with Bipolar Disorder. These findings suggest that increased volumes may reflect altered intracranial composition or potential reductions in brain parenchymal volume.

The authors note moderate between-study heterogeneity (I2 = 51%) as a limitation of the meta-analysis. While the findings provide a clearer picture of the structural differences in the brains of those with Bipolar Disorder, the clinical implications for specific treatment adjustments are not yet established. The results should be interpreted as associations between the disorder and structural volume rather than direct causal links.

How this fits prior evidence

This meta-analysis addresses a gap in the neuroanatomical profile of Bipolar Disorder. While previous coverage established that individuals with Bipolar Disorder show a significantly higher risk of dementia, this study provides specific data on the structural brain volume differences, such as increased cerebrospinal fluid and intracranial volumes, associated with the condition.

Living with bipolar disorder involves complex changes in the brain. New research looked at how the physical structure of the brain differs in adults with this condition compared to people without it. The study focused on the space inside the skull and the fluids that surround the brain.

Researchers found that people with bipolar disorder had significantly larger volumes of cerebrospinal fluid and intracranial space. They also found larger volumes in the right lateral ventricle, which is a cavity in the brain. These findings suggest that the physical makeup of the brain is different for those managing bipolar disorder.

While these results show clear differences, the data comes from a collection of different studies. This means there is some variation in the results across the board. These findings help us better understand the physical changes in the brain, even if they do not tell us exactly why these changes happen.

What this means for you:
People with bipolar disorder show larger brain fluid volumes and different internal brain structures.

Common questions

What did the study find about brain structure in bipolar disorder?

The study found that adults with bipolar disorder have significantly larger volumes of cerebrospinal fluid and intracranial space compared to others. They also showed larger volumes in the right lateral ventricle. These findings highlight specific physical differences in the brain's structure for people living with this condition.

Are these findings consistent across all patients?

The study noted significant variability in cerebrospinal fluid and intracranial volumes among individuals with bipolar disorder. Because the data came from multiple studies, there was some variation in the results, which is common when looking at complex brain structures across different groups of people.

Study Details

Study typeMeta analysis
EvidenceLevel 1
PublishedOct 2026
View Original Abstract ↓
BACKGROUND: Bipolar Disorder (BD) is a chronic, debilitating mood disorder, yet its structural neurobiology remains incompletely understood. Although prior studies have identified regional brain volumetric differences, many rely on outdated diagnostic criteria, and more recent evidence has not been systematically synthesized. Herein, we aim to meta-analytically synthesize evidence on brain structural alterations in adults with BD using DSM-IV to DSM-5-TR criteria. METHODS: Systematic search of PubMed and OVID databases was conducted from inception to February 20, 2026. Eligible studies examined structural or volumetric brain differences in adults with BD. A systematic review and meta-analysis were conducted to estimate standardized mean differences, and variability was assessed. Effect sizes were pooled using a multivariate random-effects meta-analysis. Risk of bias and heterogeneity were assessed using established methods. RESULTS: BD was associated with significantly greater cerebrospinal fluid (CSF), intracranial, and right lateral ventricle volumes compared with controls, which may reflect altered intracranial composition and potential reductions in brain parenchymal volume. Variability analyses demonstrated significantly greater variability in CSF and intracranial volumes among individuals with BD, while other regions showed no significant differences. Moderate between-study heterogeneity was observed (I² ≈ 51%), and there was no significant evidence of publication bias. CONCLUSION: These findings suggest that specific structural alterations, particularly increased CSF and ventricular volumes which may reflect underlying brain tissue loss, may characterize BD; however, substantial variability exists across individuals and brain regions. This heterogeneity highlights the complexity of BD neurobiology and underscores the need for larger, methodologically consistent studies to better characterize structural changes and their clinical implications.
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