Growing Up Poor and Stressed Impacts Brain Function as an Adult
[K. Luan Phan, Professor of Psychiatry] Over the past several decades we’ve learned that childhood poverty confers the risk of the development of negative physical and psychological health consequences throughout life. One of the major theories is that childhood poverty leads to ongoing chronic stress as the child grows up into adolescence and young adulthood, essentially setting up a cascade of increasing risk factors for them to develop these physical and psychological problems as an adult.
Besides this chronic stress model, there’s also a thought that increasing stress would have both cognitive and biological consequences and it’s thought that these cognitive and biological consequences would manifest in terms of problems with brain function.
We also know that the ability to regulate one’s emotions – having that ability – could confer protection against the negative physical and psychological health consequences but it’s unknown how childhood poverty might affect brain function particularly in the context of emotional regulation.
And the prefrontal cortex is most important here because it’s well known to be important in the ability to regulate negative affect and negative emotions and stress and that it develops during adolescence.
So in this study we were lucky to be following a cohort of individuals since the age of nine when they were characterized as being poor or not poor. And this was a longitudinal cohort led by Gary Evans at Cornell and this study is funded by a Grant Opportunity Grant from the National Institutes of Health. The principal investigators being Gary Evans, James Swain and Israel Liberzon. And I was a co-investigator and my main involvement was the contribution of concepts around emotional regulation in the context of these particular participants who are now young adults.
So we had them undergo emotional regulation tasks in a brain function scan, essentially a functional magnetic resonance scan which allows us to look their brain while it’s at work, while they were performing a task that first elicited negative emotions from pictures. And then we asked them to down regulate, or suppress, those negative emotions by using cognitive strategies that we call reappraisal which is the reframing of negative images from negative towards neutral or positive content. This is an index of our day-to-day ability to cope with stress and negative emotions as we encounter them.
So these young adults, now on average at the age of 24, were performing this task we found that how poor they were, as indexed by family income at the age of nine, predicted how well their prefrontal cortex performed while they were trying to regulate negative affect. That’s the first finding.
The second finding is that the amygdule, another region of the brain that is important for anxiety, negative emotions, and negative mood we found the opposite relationship. That low family income predicted high amygdule response during negative affect. So this is the opposite of the prefrontal cortex finding where we found that low family income at the age of nine predicted the adult’s ability to engage these prefrontal regions during affect regulation.
The third, and perhaps the most important finding, was that we found that a marker of chronic stress which we indexed by averaging exposure to multiple physical stressors such as substandard housing, crowding and noise and social stressors such as family turmoil, violence and family-child separation. That chronic stress index mediated the relationship between childhood poverty and prefrontal brain function during emotional regulation, such that that index of chronic stress explained that relationship.
So the take home message of the finding is that childhood poverty could have long lasting effects. First it leads to ongoing burden and ongoing chronic stress throughout adolescence at a time when the prefrontal cortex is developing and gaining ability to regulate negative affect as well as other cognitive functions. And secondly, that childhood poverty can predict, prospectively, the function of the brain in adults while they are trying to regulate their negative affect.
With the bottom line being that the findings highlight that childhood stress affects both the development of prefrontal cortex dysfunction as well as chronic stress, leading to a potential brain mechanism that explains the link between childhood poverty and the well documented health inequalities observed in adults originating back in childhood.