Healthy Brain, Happy Life (27 page)

I continued, “ But I want to change it. My goal is make the rest of the time that you have in the lab (he had about eighteen more months of funding left), the best and most productive time that you have ever had. That’s
my
goal, but I need to know from you what I can do to help make that shift. Can you tell me what you would like me to change about the way I do things that would help you be more productive in the lab?”

Just like my doorman, he was stunned. I remember his mouth was hanging open in surprise. But to his great credit, he managed to collect his composure and say, “Well, one thing is, I feel like you don’t give me enough credit for what I do in the lab.” I thought about this and agreed with him. One of his positive traits was that he liked to help everyone else so much, which was part of the reason he didn’t get what I asked him to do done. Instead of being grateful for his service to the lab and providing any kind word or acknowledgment, I remained annoyed at him because he was not getting his own work done. I told him he was absolutely correct and from now on I would be sure to acknowledge his contributions, and I did. There was a major change in our relationship after that conversation. Without even saying anything, he starting meeting his deadlines and making serious progress on this project. It was like another little miracle!

The amazing thing that happened was that not only did my relationship with that student change that day but the entire lab (a team of eight at the time) seemed to breathe a huge and simultaneous sigh of relief. I realized that our bad relationship had not only been stressful on the two of us but it had undeniably affected the entire lab. We all breathed easier after this conversation, and I eliminated a huge dose of daily stress that I knew was there but had no idea was so pervasive. After that conversation, it felt like there was more space, more light, and more laughter in the lab. Yes, stress is at its worst when you are not aware how deeply it’s affecting you and those around you.

RESILIENCE

A large body of research has confirmed that long-term exposure to high levels of stress is associated with higher levels of mood, anxiety, and addiction disorders. But what about those shining examples of human resilience that survive horrific conditions relatively unscathed? People like Louis Zamperini, the former Olympian and prisoner of war survivor, and John McCain, who also survived long-term imprisonment as a prisoner of war? Studies done primarily in animals have started to reveal strategies and biological responses present in resilient individuals that appear to protect them from the terrible effects of stress. These responses include the following:

•  Early life or adolescent exposure to chronic unpredictable stress helps buffer individuals from stress later in life. This phenomenon is called stress inoculation and suggests that there may be a critical period for stress exposure that helps build our antistress mechanisms. Thus there might be an optimum level of exposure for stress (typically moderate amounts of stress) at a young age that could be key to developing strong resilience as an adult.

•  In animals, stress inoculation also increases the volume of a particular part of the prefrontal cortex (ventromedial prefrontal cortex—important for emotional regulation and decision making). This is the same part of the prefrontal cortex that has been shown to shrink in both humans and rodents that have experienced excessive stress.

•  Studies in animals have identified a number of specific genes that are activated in resilient individuals in response to stress and antidepressants activate some of these same genes. This raises the possibility that we might find a wider range of ways to activate the resilience genes and better protect people against stress.

It’s an exciting time for the neurobiology of resilience and this research in animals is providing exciting new directions for both treatment for and protection from the debilitating effects of stress.

HOW EXERCISE PROTECTS AGAINST STRESS

I have just told you that stress damages the hippocampus and prefrontal cortex and shrinks hippocampal volume by damaging dendrites, decreasing neurogenesis, and ultimately killing hippocampal cells. Given all we know about the positive, enhancing effects of exercise on the anatomy, physiology, and function of the hippocampus as well as the behavioral evidence from humans that exercise enhances attention functions dependent on the prefrontal cortex, it comes as no surprise to learn that research in rodents shows that exercise not only protects the hippocampus from future stressful situations but helps reverse the damage caused by long-term stress.

These studies are typically done by exposing animals to stress, exercise on a running wheel, or both and then assessing their responses on tasks designed to elicit stress/anxiety. I’ll call it a rat stress test. For example, a number of studies have shown that rats given access to a running wheel for three to four weeks exhibit less overall anxiety than nonrunning rats on one of these rat stress tests. In other words, exercise seems to protect the rats from stressful situations that come their way. Other studies show that voluntary exercise seem to keep the rats calm and cool in a stressful situation in which nonexercised rats exhibited high levels of stress and anxiety behaviors (in rats, freezing is a typical measure of stress/anxiety).

But most of us are not sitting around waiting for stress to happen to us. We are currently in the middle of all kinds of stressful situations in our lives. What we really want to know is if we can help reverse the negative effects of ongoing stress. One of my favorite studies that addresses this question examines a particularly severe form of stress experienced by rat pups when they are separated from their mothers. When this happens, the pups exhibit stress-related responses, significant memory impairments, decreased hippocampal neurogenesis, and increased cell death in the hippocampus. However, if you put the maternally separated rat pups on a voluntary exercise regime after their separation and after they have already started to exhibit stress, you see the memory impairment go away, a reduction of the depressive behaviors, and a reinstatement of hippocampal neurogenesis.

But the key question here is,
Why
exactly is exercise relieving the detrimental effects of stress? One possible answer has to do with a theory that is gaining support called the adult neurogenesis theory of major depressive disorder. According to this theory, a decreased rate of neurogenesis is an important contributor to the depressed mood in patients with major depressive disorder. This idea is consistent with the findings that the size of the hippocampus in these patients and patients with PTSD is smaller than usual. This theory is also supported by the surprising finding that one of the initially unappreciated effects of some of the most common antidepressants is that they stimulate hippocampus neurogenesis. Not only that, but if you block the ability of the antidepressants to stimulate neurogenesis in experimental animals, the drugs don’t improve mood. This means that the ability of antidepressants to stimulate neurogenesis is an important key to their effectiveness. It also shows the importance of hippocampal neurogenesis in regulating mood in general. This gives yet another perspective on the mood-boosting power of exercise. It’s not enhancing mood only by enhancing levels of serotonin, noradrenaline, dopamine, and endorphins but also by stimulating adult neurogenesis. Incidentally, we now know that one of the previously unappreciated functions of serotonin is to stimulate neurogenesis in the hippocampus.

The adult neurogenesis theory of major depressive disorder helps us make some key links. For example, one key link is that the hippocampus is not just important for declarative learning and memory, as H.M. taught us, but also plays a key role in mood and is highly sensitive to stress. It makes sense that in rodents there is strong evidence that exercise improves memory function and decreases stress. In humans there is strong evidence that exercise decreases symptoms of depression, though the evidence for an improvement of declarative memory function is still quite weak. This means that with exercise you are getting two for one: With one activity (exercise) you get both stress reduction and cognitive improvement. And it seems to be doing both functions through the same mechanism: adult hippocampal neurogenesis.

This knowledge changed the way that I viewed exercise. At first it was something I needed for the general area of well-being in my life, something I should do if my mood and my time allowed. Now I think of it as an invaluable life tool, on the order of importance of my smartphone or my tablet. Just like my smartphone, I use exercise to make me smarter, more attentive to what I need to be attentive to, and to reduce the stress in my life. As I’ve described before, we still don’t know all the answers to exactly how exercise is improving memory or attention or mood, but you can bet that I now know how I best benefit from it in my own life. If I’m too stressed, I take an exercise break. If I have a big talk or presentation coming up, I make sure I’m feeling good, rested, and well exercised. If I don’t have time for a regular workout, I use one of my own exercise Brain Hacks or one of my favorite short workouts: the
New York Times
seven-minute workout. I now treat exercise like a tool to improve my life, and the more I learn about the neurobiology of the mechanisms at work, the more refined my prescription gets.

THE NUTS AND BOLTS OF MY NEW AND IMPROVED APPROACH TO STRESS

When I look back on how my current approach to stress developed, I have to say it started with my experience with physical exercise itself. When I was a stressed-out assistant professor working like mad to get tenure, it was exercise that first got me out of my head and got me to feel my body for the first time in a long time. It helped me regain my mind-body connection. In any exercise class, it’s difficult to focus on anything other than getting through the workout. This automatically forces you to focus on the present moment. I see now that the exercise classes were not only getting my body in shape but giving me little bursts of present-moment awareness before I went back to work and started worrying about what deadline I needed to meet or how well I wrote that last e-mail. No wonder exercise felt so good to me. It’s only in focusing in the present moment that you can really start to appreciate life as it is happening. I had too little of this in my own life and at first, these exercise sessions (which also often included a little meditation at the end) gave me my first regular taste of present-moment awareness. I have also used meditation to keep me focused on the present (see Chapter 10).

What is the key to mastering the stressful situations that I dealt with in my life? In retrospect, I believe that I was in the process of knowing myself better, knowing what I perceive as stressful (because stress is highly subjective), and becoming aware of how I deal with it or not. Part of what I was becoming aware of as I continued the process of rebalancing my life was that I no longer tolerated stagnant, chronically stressful relationships. I was actively seeking less stress and more joy in my life and was taking actions to make that intention a reality. My relationship with my doorman, with boyfriends who didn’t work out, even my previously not-so-close relationship with my parents were all stressors that I was working hard to fix, one by one.