Helping kids develop healthy habits
Could stress play an important role in children's health-related behaviours? Katie Haylor caught up with Greg Miller from Northwestern University in Chicago, who looks at how kids who come from families with fewer economic resources tend to have worse health outcomes...
Greg - We're involved in a handful of studies. Some of them are trying to understand questions about why, so, to try to pick apart the biological pathways by which growing up in a low income family, the stressors that are often associated with it, change the brain and change the body. So we bring kids in late childhood or early adolescence into our research centre, we ask them lots of questions about the stressors and the positive features in their life. So how the relationships are with their parents and with their peers, how school is going, whether they face any kind of discrimination or social exclusion or bullying. We're really interested in their day to day lived social experience.
Then, we'll draw blood from them. We'll use the blood to study their cholesterol levels and how their immune cells are functioning. We'll take their immune cells, put them into a test tube with bacteria and viruses and see how they behave. Then, on another day, we might scan their brains to look at how it's developing, what kind of structure it has, how it functions under certain tasks, and we try to put together a picture that connects their day to day social experience with how their brain is functioning and how their heart and their immune systems and their other bodily systems are functioning.
Katie - I think it's pretty well established that stress, which you mentioned just a moment ago, can affect our immune systems. Can stress affects how the brain works? Specifically in the case of kids where their brains are obviously growing?
Greg- Yes, the strongest evidence is from animal studies, but also from human studies, showing that stress does impact the brain's structure and the brain's function. This is not to say that anytime somebody has a bad day or they get into an argument with their parent, that their brain is going to be irreparably changed, but with chronic long term stress, kids can show different kinds of brain development.
Then again, we shouldn't think of this as some kind of permanent brain damage effect. The changes are subtle, consistently observed, but it isn't the case that kids who are exposed, for example, to violence in their families or in their neighbourhoods, necessarily have any kind of permanent brain damage that would preclude them from living a healthy normal life. But those kinds of experiences, if they happen on a regular basis, do lead to changes in the brain's grey matter, the volume of certain regions of the brain like the amygdala, that's involved in responding to threats, the hippocampus, involved in long term memory and regulating stress responses, and also the prefrontal cortex, which is involved in a lot of the things that make us human around regulating our own behaviour and thinking. Stress can change all of those areas, and probably more critically, the way those different regions of the brain talk to each other.
Katie - How does stress do that?
Greg - We know that stress causes fairly substantial changes in the release of hormones to the rest of the body. So, stress related changes in adrenaline, noradrenaline and cortisol, and we're all pretty familiar with the fact that those hormones do things like speed up the rate of your heart, cause your heart to contract more forcefully, so these are metabolic changes and changes in the way that many organs like the heart and the lungs function, that prepare you or allow you to fight or flee more effectively.
Well some of those hormones we also know travel to the brain and can change the way brain cells communicate with each other, there's also a whole set of hormones that are released specifically in the brain under conditions of stress that with prolonged and repeated bouts of stress, those hormones can again change communication between cells, change the structure of networks between different regions of the brain, essentially at a basic level the wiring diagram of the brain.
Katie - So, how does this relate to these everyday, really difficult problems like eating too much, drinking too much, or smoking?
Greg - So many of us recognize that when we have a lousy day, oftentimes we’ll cope with our frustration or sadness or anxiety by doing things that feel good. One of those things is often eating. Oftentimes stress promotes the kinds of unhealthy behaviours you're asking about by changing activity in parts of the brain that are involved in decision making, in seeking out rewards, seeking out pleasurable activities. There's a lot of work done in rats and some in monkeys and some in humans, that when you put it all together suggests that stress, especially these long term stresses, definitely change the way that our brain seeks out and responds to pleasurable stimuli. And also changes those decision making regions of the brain in ways that make it harder, potentially, to resist a pleasurable stimulus like a milkshake or a beer.
Katie - And so is part of the motivation for looking at how this works in kids' brains because they are obviously juvenile, so if they have chronic illnesses it's going to be affecting them for an awful long time?
Greg - Yeah. That's part of it. The other part is that the brain and a lot of the other organs in the body have a lot of plasticity in childhood and adolescence, and by plasticity I mean the capacity for change and development. A lot of the more serious health problems don't arise in childhood. They begin in childhood, but they don't manifest clinically until much later. So, the classic example of this would be heart disease, which often shows up in the form of a heart attack or a stroke when people are in their 60s or 70s or 80s, but we know from autopsy studies that heart disease itself begins often in mid to late adolescence.
Katie - If kids' brains have this plasticity in comparison to adult brains, does that mean there’s a bit more hope for interventions?
Greg - Yeah, I think many of us who are developmentalists believe that the return on investment for interventions in childhood is going to be quite high relative to other points in the lifespan. In part, it's because of the plasticity that you refer to, in part it's because any return on investment has a lot of time to compound, and it's in part because kids' health is pretty good so they're not so far down the path to overt disease that an intervention might create some kind of fork in the road, where you wouldn't have an opportunity for that much change in an older adult where, say, the underlying pathophysiology of disease, the amount of plaque, was already pretty significant.
Katie - Have you had any hints at potential interventions?
Greg - Yeah. We've had some luck working with collaborators focusing on building strong family relationships and strong communities. It's tough for kids to make substantial behaviour change on their own. Kids often don't have a lot of flexibility about what they eat, about when they engage in physical activity, a lot of those things are determined by the family they live in, the community they live in, the neighbourhood they live in, the school they go to. And also developmentally it's just hard for kids to enact the kinds of goal setting and follow through that's required for sustained behavioural change.
Working through their families and through their schools and through their communities, we can use older kids as role models and adults, sometimes parents, sometimes extended family members, sometimes teachers, as scaffolds that can help kids make these sort of sustained changes, or find different kinds of meaning in challenges they may face, in ways that help them not necessarily see the stress in their lives as permanent, not to see it as as big of a threat and to reinterpret it and cope with it in a manner that is less likely to cause health problems down the line. So, instead of going and drinking a milkshake after an argument with a friend, to go out and play basketball for an hour or release stress in other, more productive ways.
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