Friday, August 24, 2018

Lower White Matter Density at Age 14 May Signal Future Depression

Adolescents with a lower density of white matter—the nerve fibers that connect different brain regions—are at higher risk of developing depression, according to a report in AJP in Advance.

Previous research has shown that adolescents with depression have reduced white matter density. This new study shows that these structural changes predate the onset of depression, suggesting they may represent a biomarker of depression vulnerability.

Researchers with Europe’s IMAGEN Consortium took brain scans of 96 14-year-olds with subthreshold depression and 336 age-matched healthy controls. The participants were categorized as having subthreshold depression if they had experienced at least three depressive symptoms, including at least one core symptom (abnormally depressed, irritable mood, or loss of interest) in the past four weeks, without fulfilling criteria for a DSM-IV major depressive episode. The adolescents then had a follow-up assessment at age 16 to screen for depression and other psychiatric disorders (no brain scans were taken during follow-up).

The investigators used a technique called fractional anisotropy to measure the density of nerve fibers in the brains of the adolescents. They found that on average those with subthreshold depression at age 14 had lower fiber density, particularly in two regions: the corpus callosum (the band of nerves that joins the two hemispheres of the brain) and the nerve fibers that connect the corpus callosum to the anterior cingulate cortex (a brain region that mediates behaviors such as attention and reward anticipation).

This reduced nerve fiber density was more pronounced in the adolescents who developed depression by 16. The researchers developed an algorithm that identified adolescents who developed depression with about 75% accuracy.

Previous studies have suggested that white matter changes may be associated with other psychiatric disorders in adolescents, including generalized anxiety disorder and attention-deficit/hyperactivity disorder, the authors wrote. According to their analysis, reduced nerve fiber density “did not predict higher risk for any diagnosis other than depression at follow-up,” the authors noted.

They confirmed the association between reduced nerve fiber density and depression risk in an independent set of 686 adolescent brain scans (all from adolescents without psychiatric disorders at baseline) that were part of the IMAGEN database. “[O]ur imaging findings appear to be specific to increased risk for depression,” they wrote.

For more information on depression in adolescents, see the Psychiatric News article “Brains of Teen Girls Resilient to Depression Differ From Brains of Others.”

(Image: iStock/wenht)


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