Depression can be debilitating. Considered the leading cause of disability by the World Health Organization the disease is felt by an estimated 350 million people around the world—and does not just affect adults.

A new study published today in JAMA Psychiatry, has highlighted that the mental disorder can be experienced by children as young as 3-years-old, with devastating cognitive affects: Depression actually alters the way a child’s brain develops.

A team of researchers out of Washington University School of Medicine in St. Louis studied 193 kids as they went through adolescence. Close to half had been diagnosed with depression in preschool. Three MRI scans were conducted starting when the children were between the ages of 6 and 8, and ending in their early teenage years.

The scans showed that the children who had depression also had lower volumes of gray matter in their brains as they grew up.

Gray matter is an important brain tissue, made mainly of neurons, that help connect and process information. It is used for seeing, hearing, memory, and processing emotion. Healthy children build gray matter in the brain until puberty. At that point, neurons no longer need the tissue to efficiently make cognitive connections and pruning begins—a process that enables the brain to slough off the unnecessary cells.

But for kids who were depressed, pruning begins much sooner—and the problem gets proportionately worse with how severely depressed the child was. The researchers found that those kids struggled to regulate their emotions later in life.

“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 lead researcher Joan L. Luby, in a statement released with the study. “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.”

Luby’s study isn’t the only to focus on how life experience can change cognitive development. Research out of Columbia University shows similar results from stressors caused by low socioeconomic status.

A team lead by pediatrician and neuroscientist Kimberly Noble found that kids growing up in poverty had much different brain structures than wealthier children. These differences correlated with problems in reading, vocabulary, memory, and problem solving.

“We found that family income and parental education were associated with the size of the circle on top—that’s the surface area that results from all the nooks and crannies of the surface of the brain,” Noble explains in an interview with science magazine Nautilus. She emphasized the importance of early-intervention to help mitigate the effects of inequality.

Luby has also called for better strategies to target depression in children. She and her team plan to conduct more scans to identify whether or not treatment will help revert the negative effects, but says that their findings highlight the importance of counteracting the condition.

“The experience of early childhood depression is not only uncomfortable for the child during those early years,” she says. “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.”