As a psychiatrist, I’ve long wondered why some people get ill in the face of stress and adversity — either mentally or physically — while others rarely succumb.
We know, for example, that not everyone gets post-traumatic stress disorder after exposure to extreme trauma, while some people get disabling depression with minimal or no stress. Likewise, we know that chronic stress can contribute to physical conditions such as heart disease and stroke in some people, while others emerge unscathed. What makes people resilient, and is it something they are born with or can it be acquired later in life?
New research suggests that one possible answer can be found in the brain’s so-called central executive network, which helps regulate emotions, thinking and behaviour. In a study published last month, Dr Gregory Miller, a psychologist at Northwestern University, and colleagues there and elsewhere used MRI to study the brains of a racially diverse group of 218 people, ages 12 to 14, living in violent neighbourhoods in Chicago. They reported that the youths who had higher levels of functional connectivity in the central executive network had better cardiac and metabolic health than their peers with lower levels of connectivity.
What Miller and his colleagues discovered was that when neighbourhood homicide rates went up, the young people’s cardiometabolic risk — as measured by obesity, blood-pressure and insulin levels, among other variables — also increased, but only in youths who showed lower activity in this brain network. This was true even when the researchers controlled for other factors, like psychological distress, economic status, race or ethnicity. No link was found between brain connectivity and cardiometabolic health for youths in neighbourhoods with low levels of violence.
One plausible explanation is that greater activity in this network increases self-control, which most likely reduces some unhealthy behaviours people often use to cope with stress, like eating junk food or smoking.
What’s curious is that the more medically hardy young people were no less anxious or depressed than their less fortunate peers, which suggests that while being more resilient makes you less vulnerable to adversity, it doesn’t guarantee happiness — or even an awareness of being resilient.
Of course, this is an observational study, so it cannot prove that the correlation between brain connectivity and health is causal. (It is possible, for example, that baseline cardiometabolic status affected brain connectivity, but it would be hard to understand why this would be observed only in high-violence areas.)
Still, there is good reason to believe the link may be causal because other studies have found that we can change the activity in the self-control network, and increase healthy behaviours, with simple behavioural interventions. For example, mindfulness training, which involves attention control, emotion regulation and increased self-awareness, can increase connectivity within this network and help people to quit smoking.
In one study, two weeks of mindfulness training produced a 60 per cent reduction in smoking, compared with no reduction in a control group that focused on relaxation. An MRI following mindfulness training showed increased activity in the anterior cingulate cortex and prefrontal cortex, key brain areas in the executive self-control network.
Clearly self-control is one critical component of resilience that can be easily fostered. But there are others.
Dr Huda Akil, a neuroscientist at the University of Michigan who studies the biology of stress and resilience, said in a recent speech: “Active resilience happens when people who are vulnerable find resources to cope with stress and bounce back, and do so in a way that leaves them stronger, ready to handle additional stress, in more adaptive ways.”
Akil discovered that there are brain molecules that endow us with resilience. For a paper published in 2011, she and, she and colleagues studied the brains of depressed patients who died. They found that the most disrupted genes were those for growth factors, proteins that act like a kind of brain fertiliser.
“We came to realise that depressed people have lost their power to remodel their brains. And that is in fact devastating because brain remodelling is something we need to do all the time — we are constantly rewiring our brains based on past experience and the expectation of how we need to use them in the future,” Akil said.
Once again, it seems resilience is related to brain connectivity.
Akil and colleagues at the Pritzker Neuropsychiatric Disorders Research Consortium found that one growth factor that is depleted in depressed brains, called fibroblast growth factor 2, also plays a role in resilience. When they gave it to stressed animals, they bounced back faster and acted less depressed. And when they gave it just once after birth to animals that had been bred for high levels of anxiety and inhibition, they were hardier for the rest of their lives.
Another growth factor, BDNF, promotes neurogenesis in animals and may enhance resilience in humans. The good news is that we have some control over our own brain BDNF levels: Getting more physical exercise and social support, for example, has been shown to increase BDNF.
There is much still to learn about the science of resilience. Perhaps someday we might be able to protect young people exposed to violence and adversity by supplementing them with neuroprotective growth factors. We know enough now to help them by fortifying their brains through exercise, mindfulness training and support systems. And of course we should do all we can to makes these stressful environments less harmful.
Some people have won the genetic sweepstakes and are naturally tough. But there is plenty the rest of us can do to be more resilient and healthier.
-New York Times News Service