Childhood depression may result in abnormal brain development and lifetime mental health problems, according to a new study published in JAMA Psychiatry.

Children's brain development may begin in utero, but neuroscientists are increasingly interested in how the brain develops during school-age and early adolescence. Evidence shows our experience (negative moods, parental abscence) can have an adverse impact on brain growth and development, like decreased cortical gray matter. Yet very few longitudinal studies have been focused on finding links between an experience like early childhood depression and altered brain development.

For the study, researchers used data from 193 children participating in an 11-year longitudinal of preschool depression from September 2003 to December 2014; 90 were diagnosed as preschoolers. Participants underwent clinical evaluations as they got older, getting assessed on everything from their behavior to demographic, psychosocial (stress and traumatic life events), and developmental characteristics. These assessments included magnetic resonance imaging at three points throughout a child's life — ages 6 to 8 and 12 to 15.

"If we had only scanned them at one age or stage, we wouldn't know whether these effects simply were present from birth or reflected an actual change in brain development," said co-investigator Dr. Deanna M. Barch, head of Washington University's department of psychological and brain sciences, in a press release. "By scanning them multiple times, we were able to see that the changes reflect an actual difference in brain maturation that emerges over the course of development."

Of the 193 participants, 90 had lifetime major depressive disorder (MDD). Barch and her team found "marked bilateral decreases in thickness of cortical gray matter" and in volume of the right hemisphere associated with mean level of depressive symptoms and MDD diagnosis from preschool to school age. Put it another way: Children with depression experienced greater reduced volumes of gray matter at almost twice the rate of children who did not have depression. Cortical thickness also decreased at a more rapid rate than those not diagnosed with early depression.

"We speculate that changes in cortical gray matter related to childhood depression may reflect experience-dependent neuroplasticity," researchers wrote. "However, the study was not designed to definitively inform whether the cortical changes were related to depression-based experience-dependent plasticity vs. other genetic or psychosocial processes. Nonetheless, the current findings are consistent with an experience-dependent process given the fact that a family history of depression, a putative marker of family genetic risk, was not related to trajectories of cortical gray matter."

Gray brain matter contains most of the brains cells and it’s involved in muscle control and sensory perception, such as seeing, hearing, memory, and emotions. We develop more gray matter as we grow, until we hit puberty and trigger a process called pruning, Barch explained; the unnecessary cells die off. In children with depresison, there seemed to be "a much steeper drop-off, possibly due to pruning." These findings may be able to explain why both children and adults have trouble regulating their moods and emotions.

"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," said first study author Dr. Joan L. Luby, whose research established that children as young as 3 can experience depression. "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."

Next, researchers want to conduct brain scans on even younger children and determine whether early intervention might shift the trajectory of brain development. As is, they believe their study signals the need for greater public health attention and screening for early childhood depression.

Source: Luby JL et al. Early Childhood Depression and Alterations in the Trajectory of Gray Matter Maturation in Middle Childhood and Early Adolescence . JAMA Psychiatry. 2015.