From The Quarterly, May 2016

Over the past decade, it has become clear that even very young children can suffer from clinical depression. Now, research published December 16, 2015 in the journal JAMA Psychiatry suggests that early childhood depression can impact the course of brain development, underscoring the importance of identifying and treating children with the disorder.

According to the study, which followed children diagnosed with major depressive disorder between the ages of three and six, early childhood depression is associated with disruptions in brain development that continue into early adolescence. Periodic brain imaging revealed that in comparison with children unaffected by the disorder, children who had suffered from depression in their preschool years had lower volumes of gray matter—which contains the neural connections through which brain cells communicate—in the cortex of their brains. This change may have a lasting effect on emotional processing and make a child vulnerable to problems later in life, the researchers say.

Joan L. Luby, M.D., a 2004 and 2008 Independent Investigator and Young Investigator in 1999, now at Washington University in St. Louis, has led research establishing that depression can occur in children as young as three years-old. Like adults with major depressive disorder, preschool-aged children with depression experience changes in sleep, appetite, and activity level and an inability to experience pleasure. These symptoms often continue later in childhood.

In the new study, Dr. Luby and her team, including 2013 Distinguished Investigator Deanna M. Barch, Ph.D., (also a 1995 and 2000 Young Investigator, 2006 Independent Investigator), along with 1997 Young Investigator and 2005 Independent Investigator Kelly N. Botteron, M.D., also at Washington University, wanted to understand whether those early experiences of depression impact brain development.

To find out, the researchers followed a group of 193 children, including 90 diagnosed with major depressive disorder during their preschool years, for up to 11 years. The scientists used magnetic resonance imaging (MRI) to watch how activity in each child’s brain changed as he or she aged. Up to three scans were collected for each child, beginning between the ages of six and eight and with the final scan occurring between the ages of 12 and 15.

The brain’s gray matter begins to form before birth, but continues to develop during childhood, reaching its greatest volume around puberty. After this peak, cells are pruned back to eliminate redundant connections, reducing gray matter volume. The research team observed this normal and expected decline in gray matter in all the children in their study, but it was most dramatic in those who had suffered depression. What’s more, the decline was steepest in those whose depression symptoms had been most severe.

The researchers stress that further research is needed to identify effective ways to treat depression in young children and to determine whether early intervention can restore normal patterns of brain development.