White Matter Alterations in Depressive Disorder

Summary & key facts

This paper is a short review of studies that look at how depressive disorder is linked with changes in the brain’s white matter. White matter is the brain’s wiring made of nerve fibers wrapped in myelin, and researchers find differences on brain scans, blood tests, and animal experiments. The review says several things could explain those differences: reduced blood flow in parts of the brain, poor ability to regulate that blood flow, a leaky blood-brain barrier that lets inflammatory molecules in, higher inflammation, and a mix of genes and life experiences. The authors also note that white matter differences relate to how severe depression is and to treatment response, but we do not yet know which comes first or exactly how these changes cause symptoms.

Key facts:

• White matter means the brain’s bundles of nerve fibers covered in a fatty layer called myelin, and many studies find that people with depressive disorder often show changes in that white matter on brain scans.
• Lower blood flow in certain white matter areas has been found in people with depression compared with people without depression, and scans also show that more visible white matter damage is linked with lower blood flow.
• Depression seems to weaken the body’s systems that keep brain blood flow steady, and worse regulation of blood flow is linked with worse white matter structure.
• Many people with depression have higher levels of inflammatory molecules in their blood, and some studies link higher inflammation to more white matter damage and to lower measures of white matter integrity on scans.
• Research in animals and some human studies suggest the blood-brain barrier can become more permeable in depression, which could let inflammatory factors into the brain and damage white matter.
• Genes and environmental factors both play a role. Twin and family studies suggest depression is about 30% to 40% heritable, and some gene-related changes are linked with white matter differences in depressed people.
• The review finds that white matter changes are associated with clinical features such as diagnosis, severity, and how people respond to treatment, but it does not establish that white matter changes cause depression or that fixing them will cure symptoms.

Abstract

Depressive disorder is the most prevalent affective disorder today. Depressive disorder has been linked to changes in the white matter. White matter changes in depressive disorder could be a result of impaired cerebral blood flow (CBF) and CBF self-regulation, impaired blood-brain barrier function, inflammatory factors, genes and environmental factors. Additionally, white matter changes in patients with depression are associated with clinical variables such as differential diagnosis, severity, treatment effect, and efficacy assessment. This review discusses the characteristics, possible mechanisms, clinical relevance, and potential treatment of white matter alterations caused by depressive disorders.

Topics

Functional Brain Connectivity Studies Stress Responses and Cortisol Tryptophan and brain disorders

Categories

Biological Psychiatry Life Sciences Neuroscience

Tags

Cerebral blood flow Cognition Depression (economics) Economics Internal medicine Macroeconomics Magnetic resonance imaging Major depressive disorder Medicine Psychiatry Psychology Radiology White matter

Conditions & symptoms

Depression Difficulty focusing Lack of energy or motivation Poor sleep Sadness or low mood