Protect your brain from stress

Stress management may reduce health problems linked to stress, which include cognitive problems and a higher risk for Alzheimer's disease and dementia.

 Image: © iMrSquid/Getty Images

It's not uncommon to feel disorganized and forgetful when you're under a lot of stress. But over the long term, stress may actually change your brain in ways that affect your memory.

Studies in both animals and people show pretty clearly that stress can affect how the brain functions, says Dr. Kerry Ressler, chief scientific officer at McLean Hospital and professor of psychiatry at Harvard Medical School. Scientists have seen changes in how the brain processes information when people experience either real-life stress or stress manufactured in a research setting. (For the latter, researchers might challenge subjects to perform a difficult task, such as counting backward from the number 1,073 by 13s while being graded.) Either type of stress seems to interfere with cognition, attention, and memory, he says.

Stress affects not only memory and many other brain functions, like mood and anxiety, but also promotes inflammation, which adversely affects heart health, says Jill Goldstein, a professor of psychiatry and medicine at Harvard Medical School. Thus, stress has been associated with multiple chronic diseases of the brain and heart. In addition, it can affect men and women differently, she says.

Stress and the brain

To understand why stress affects thinking and memory, it's important to understand a little about how the brain works. Your brain isn't just a single unit, but a group of different parts that perform different tasks, says Dr. Ressler. Researchers believe that when one part of your brain is engaged, the other parts of your brain may not have as much energy to handle their own vital tasks, he says. For example, if you are in a dangerous or emotionally taxing situation, the amygdala (the part of your brain that governs your survival instincts) may take over, leaving the parts of your brain that help to store memories and perform higher-order tasks with less energy and ability to get their own jobs done. "The basic idea is that the brain is shunting its resources because it's in survival mode, not memory mode," says Dr. Ressler. This is why you might be more forgetful when you are under stress or may even experience memory lapses during traumatic events.

The effect that stress has on the brain and body may also differ depending on when it occurs in the course of someone's life, says Goldstein. Certain hormones, known as gonadal hormones — which are secreted in large amounts during fetal development, puberty, and pregnancy and depleted during menopause — may play a role in how stress affects an individual, says Goldstein. "For example, reductions in the gonadal hormone estradiol during the menopausal transition may change how our brain responds to stress," she says.

Long-term brain changes

There is evidence that chronic (persistent) stress may actually rewire your brain, says Dr. Ressler. Scientists have learned that animals that experience prolonged stress have less activity in the parts of their brain that handle higher-order tasks — for example, the prefrontal cortex — and more activity in the primitive parts of their brain that are focused on survival, such as the amygdala. It's much like what would happen if you exercised one part of your body and not another. The part that was activated more often would become stronger, and the part that got less attention would get weaker, he says. This is what appears to happen in the brain when it is under continuous stress: it essentially builds up the part of the brain designed to handle threats, and the part of the brain tasked with more complex thought takes a back seat.

These brain changes may be reversible in some instances, says Dr. Ressler, but may be more difficult to reverse in others, depending on the type and the duration of the stress. While stressful childhood experiences seem to take more of a toll on the developing brain, some research has found that people who demonstrate resilience in the face of past childhood trauma actually appear to have generated new brain mechanisms to compensate. It's thought that these new pathways help to overcome stress-related brain changes that formed earlier in life, he says.

Is all stress created equal?

While the effect of stress on the brain is well documented, it's less clear exactly what type of stress will prove damaging and raise the risk of memory problems later in life. Do brain problems occur when you are under a small amount of stress or only when you experience long-term stress?

"That's a tough question, because stress is a broad term that is used to describe a lot of different things," says Dr. Ressler. The stress you might experience before you take a test is likely very different from the stress of being involved in a car accident or from a prolonged illness. "Certainly, more stress is likely worse, and long-term stress is generally worse than short-term stress," says Dr. Ressler.

But there are additional factors that make stress more harmful, he says. In particular:

• The stress is unpredictable. Animal research shows that animals that could anticipate a stressor — for example, they received a shock after a light turned on — were less stressed than animals that received the same number of shocks randomly. The same is true in humans, says Dr. Ressler. If a person can anticipate stress, it is less damaging than stress that appears to be more random.

• There is no time limit on the stress. If you are stressed about a presentation at work or an upcoming exam, the stress you are experiencing has an end point when you know you will get relief. If the stress has no end point — for example, you are chronically stressed about finances — it may be more challenging to cope with.

• You lack support. If you feel supported during your stress, you are likely to weather it more successfully than if you don't.