Childhood obesity and depression in children may be driven by shared abnormalities in brain regions that process rewards, according to researchers at the Stanford University School of Medicine.

Brain MRI scans of kids ages 9 to 17 who struggled with depressive symptoms and maintaining a healthy weight showed young people who had both conditions had low volumes in two of the brain’s reward-processing areas, the hippocampus and anterior cingulate cortex. The participants’ brain abnormalities also were linked to their level of insulin resistance, itself a precursor to diabetes.

The researchers recruited 42 young participants with a BMI greater than the 85th percentile who also had moderate-to-severe untreated depressive symptoms. Prior to seeking treatment, the children, aged 9 to 17, were assessed with standard clinical tests and questionnaires to evaluate their level of depression, their experience of pleasure and certain eating behaviors, such as uncontrolled eating and emotional eating. They also had their insulin resistance measured while fasting and after consuming a standard dose of glucose, the sugar in our blood. They were then underwent brain scans.

Prior brain-scan research examining childhood obesity or depression linked each condition individually to abnormalities in the brain’s reward centers.

“Independently, in obesity and depression, the same brain networks popped up, and that was curious to us,” said the study’s lead author, Dr. Manpreet Singh, a child and adolescent psychiatrist. “We thought maybe that was a link that would help us understand better why these symptoms coexist.”

The characteristics of the participants’ hippocampus and anterior cingulate cortex correlated to their levels of insulin resistance and also to their degree of depression, with lower volumes of the two brain regions in children and teens who had more insulin resistance or severe depression, or both.

“With this new study, we are trying to understand the earliest age at which this vulnerability begins, and also the earliest time we will be able to intervene when we find the appropriate intervention,” said the study’s senior author, Dr. Natalie Rasgon, a professor of psychiatry and behavioral sciences. “Early intervention is important because, later in life, these are the same brain areas which will ultimately be vulnerable to neurodegenerative processes as well. It’s a double whammy.”

When obesity and depression begin in childhood, they tend to persist throughout life. Depressed youth may experience a cycle of overeating to try to make themselves feel better, followed by weight gain, ongoing depressed feelings and weight-related bullying that further worsens their depression.

Singh’s team is now conducting a longitudinal study of a cohort of children and teens, including the participants from this just-completed study, to assess how their brains and clinical symptoms track together over time.

“We want to help children and families understand that these conditions are brain-based phenomena,” Singh said.

Children and teens who have both conditions often feel stigmatized and may hesitate to pursue treatment, Singh said. “We want to destigmatize these issues. Understanding that there’s a brain basis may help both children and parents be solution-focused.”