Ian Gotlib is convinced that by learning to spot predictors of depression as soon as possible, psychologists can one day help prevent the disorder.
By Ker Than
Ian Gotlib has spent years compiling a growing catalog of clues that could help to identify children who are at increased risk for developing depression later in life. The list includes everything from size differences in structures tucked deep within the brain to a predilection for sorrowful faces.
The Stanford professor of psychology is convinced that if psychologists can learn to spot these “predictors of depression” early, they may one day be able to prevent a mental disorder that affects more than 16 million Americans every year from happening in the first place.
“The average number of discrete episodes of depression over a lifetime is five or more,” said Gotlib, who is also the David Starr Jordan Professor in Stanford’s School of Humanities and Sciences. “If we can prevent the first episode, we can prevent a significant negative cascade.”
The signs Gotlib seeks are subtle. They are hidden in the children’s brains and bodies, in their genes and the subconscious, or automatic, ways they respond to stress. They also manifest early – often years before the children ever exhibit symptoms that would warrant a clinical diagnosis of depression. No one really knows just how early the signs can appear, so Gotlib’s lab began studying hair from expectant mothers.
Like tree rings or light from a distant galaxy, the strands of hair are time capsules. Each centimeter of hair captures about one month’s average cortisol production. A 4- to 5-centimeter hair sample, collected before a baby is born and once more a few weeks after birth, can provide monthly cortisol levels for a woman’s entire nine-month pregnancy.
Often called the “stress hormone,” cortisol is released by our bodies during times of emotional and physical duress to help regulate our moods, motivations and fears. Gotlib and others have shown that early life stress can alter cortisol levels, which in turn can reduce the size of the hippocampus, part of the brain that plays an important role in learning and memory. A smaller hippocampus has been linked to greater risk of depression, anxiety, suicidal behavior and other mental disorders in later life. A recent study in Developmental Science, led by Kathryn Humphreys, an assistant professor at Vanderbilt University and a former postdoctoral fellow in Gotlib’s lab, found that hippocampal growth is especially sensitive to stress during the first five years of a child’s life.
Gotlib now seeks to understand how maternal cortisol levels during pregnancy affect a developing infant’s brain from in utero to at least 18 months of age by monitoring and measuring their responses in stressful situations.
Researchers in Gotlib’s lab are also assessing whether parental warmth and sensitivity make a difference by recording everything the baby hears. Using software to separate adult speech from baby babble and extraneous noise, they can paint a sonic picture of the parent-child bond. “We can get basic measures of how many adult words are spoken near the infant and how many times the infant vocalized in response,” said Stanford graduate student Lucy King, who is involved in the project.
By combining data about cortisol exposure in the womb, infant neuroimaging and parental behavior, Gotlib’s lab aims to disentangle the complex web of factors that can influence a child’s psychobiological responses to stress and their risk for depression in later life.
“We want to know, what are the relative effects of the pre-birth versus postnatal environments on infant brain development?” King said. “And can enrichment postnatally remediate the effects of a negative prenatal environment?”
In other words, can the actions of a parent or caretaker help assuage the marks of early life stress and shield a child against developing emotional difficulties like depression in adulthood?