Early childhood depression is associated with marked alterations in cortical gray matter in late school age and early adolescence, a newhas found
Researchers from Washington University School of Medicine, St Louis, Missouri, USA analysed data from 193 children aged three to six years involved in an ongoing 11-year longitudinal study. Ninety of the children have a diagnosis of major depressive disorder.
The team, led by Professor Joan L Luby MD, performed clinical evaluations on the children several times as they aged. They also conducted MRI scans at three points in time as each child got older. The first scans were performed when the kids were six to eight years of age; the final scans were taken when they were 12 to 15. A total of 116 children in the study received all three brain scans.
The researchers found that that childhood depressive symptoms were associated with decline in volume and thickness of cortical gray matter even after accounting for other key factors known to affect this developmental process. They also found that the more depressed a child was, the more sever the loss in volume and thickness.
‘What is noteworthy about these findings is that we are able to see how a life experience — such as an episode of depression — can change the brain’s anatomy,’
Professor Luby said.
‘Traditionally, we have thought about the brain as an organ that develops in a predetermined way, but our research is showing that actual experience — including negative moods, exposure to poverty, and a lack of parental support and nurturing — have a material impact on brain growth and development.’
Gray matter is made up mainly of neurons, along with axons that extend from brain cells to carry signals. It processes information, and as children get older, they develop more of it. Beginning around puberty, the amount of gray matter begins to decline as communication between neurons gets more efficient and redundant processes are eliminated.
‘Gray matter development follows an inverted U-shaped curve,’
Professor Luby explained.
‘As children develop normally, they get more and more gray matter until puberty, but then a process called pruning begins, and unnecessary cells die off. But our study showed a much steeper drop-off, possibly due to pruning, in the kids who had been depressed than in healthy children.’
The study concludes:
‘These findings of markedly increased rates of cortical volume loss and thinning across the entire cortex underscore the importance of attention to childhood depression as a marker of altered childhood cortical brain development. Whether these early alterations serve as an endophenotype of risk for later depressive episodes or chronic course is a question of interest as the study sample is followed up through adolescence. The study findings signal the need for greater public health attention and screening for depression in young children.’
Professor Luby added:
’The experience of early childhood depression is not only uncomfortable for the child during those early years,” she said. ‘It also appears to have long-lasting effects on brain development and to make that child vulnerable to future problems. If we can intervene, however, the benefits might be just as long-lasting.’