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The vicious physiology of stress
One of my favorite parts of this job is stalking busy scientists researching different aspects of stress.
I recently tracked down the brilliant Dr. Rajita Sinha, director of the Yale Stress Center, and spoke to her about what she’s working on. In this first part of our conversation, we discussed the physiology of stress and its connection to maladies, ranging from addiction to chronic disease, diabetes and obesity.
How did you come to study stress?
Early on I was working with different types of emotions - anger and sadness - and how they affect the body and change our responses to different stimuli in the environment. One of the things I observed was that generally people don’t have pure emotions, like anger or fear.
They mostly have mixed emotions. If you ask them about it, they will say they’re stressed and upset. I wanted to understand how emotions work together - both to protect us and to feed into things that wear us down.
Is there such a thing as good stress?
Think about good stress in terms of adaptation. Every time you overcome a challenge and learn something from it, it leads to cognitive and behavioral adaptation. It’s like skill building. When a challenge is frustrating but within our ability to handle it, you are talking about a good stress. It’s stress that is sustained, uncontrollable and overwhelming, where people can’t figure out options to solve their problems, that is damaging.
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Can you tell me about the link between stress, chronic disease and addictive behavior?
We’ve known about the link between stress and addiction, and increased susceptibility to chronic diseases for a long time. But we have not fully understood the biological mechanism until recently.
When we experience something threatening or stressful, two things happen immediately. The first thing is what we call the "fight or flight" arousal response. The whole body is gearing up to move quickly to get out danger. And the second thing is that the body releases the stress hormone cortisol. The body gears up immediately in the face of stressful stimuli. It goes to our energy stores, and releases glucose and insulin so that our muscles have the energy to deal with the stress.
Here’s where the rubber hits the concrete, in terms of our choices. Drugs like alcohol, nicotine and cocaine, and also high-fat, high-calorie comfort foods, are powerful modifiers of the stress system. They will change our stress pathways and affect the way our body is able to control our stress response. And so, after a period of bingeing, your body’s stress system eventually just wears out.
Your adrenal gland, which is responsible for releasing the stress hormone, becomes weak or sputters out. Then it doesn’t signal properly to help us cope. That, in turn, starts to affect us adversely - not just our biology, but also our emotional response.
Can you reinvigorate worn-out adrenals?
There is evidence that you can reinvigorate your adrenals. Once alcohol dependents start recovering, after some time has passed, you start seeing adrenals returning to normal. We know less about how long it takes.
The problem, though, is that while your adrenals are still recovering, you are more likely to be stressed. And stress affects abstinence and increases chances of a relapse. So then you are caught in a vicious cycle of quickly degenerating health because both the stress and the substances are working together to wear down your body systems—your stress axis, your liver, kidney, heart, blood pressure.
Then you get a double whammy in terms of risk for heart disease and certain types of cancer. It’s what we call the feed-forward effect. It’s not going to happen immediately, but it does become a vicious cycle.
Which comes first, the stress or the addictive behavior?
We don’t really know which comes first, but we do know that these are all complex multi-factoral diseases. That means they don’t have one single factor that leads to the disease state. And there are factors that can make a person even more vulnerable to stress-related diseases and addiction: early trauma suffered in childhood, cumulative adversity, socio-economic status, education and also things like genetics and personality traits.
Which aspect of your research are you most excited about right now?
We’re about to release a paper about how cumulative adversity - the number of bad things happening in one’s life - appears to have an effect on the size of the brain’s prefrontal cortex.
What does that mean? Is that a good or bad thing?
It means the higher number of bad events, the smaller the size of the prefrontal cortex. And our animal studies show that less volume in the prefrontal cortex is not good behaviorally. Neurons start shrinking and lose their branches and dendrites. Those animals don’t do well in different kinds of cognitive tasks. So what that means is that higher levels of adversity affect our ability to respond to acute stress situations.
It has two effects: There is less brain volume and the regions that help us adapt and cope are underactive.The more lifetime adversity, the higher amount of chronic stress that a person feels. Then the risk for stress-related disorders go up: heart disease, diabetes, certain types of cancer, psychiatric and neuropsychiatric disorders like depression, anxiety and addiction.
Well, that’s depressing for those of us who’ve been through a lot in life through no fault of our own.
An interesting follow-up is that the brain is very dynamic and there may be potential for normalizing or regrowth. The studies we did are with people between 18 and 50. These are our most generative years, so we hope we can intervene, through treatments, to turn the course.
How can we train ourselves to respond better to stressors?
We live in a society where there are multiple demands on us almost all the time. We need to put greater emphasis on protective factors like sitting down with the family or exercising or putting away all the electronic devices.
I am also a big believer in mindfulness. I think we need to be able to turn things down and off, and build in protections so that we don’t get overwhelmed - even something as simple as a hobby.
I was on a show once where someone had joined a drumming class to relieve stress. It’s a matter of taking the time to build in positive aspects to our life, our actions and our exposure. That’s like money in the bank. |
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发表于 2017-8-5 22:03:21