Nervous System

How can ongoing stress affect your memory?
Answered by Jennifer Horton and Science Channel
  •  Jennifer Horton

    Jennifer Horton

  • Science Channel

    Science Channel

  1. Ever noticed how you seem to conveniently forget key pieces of information during tense moments? If you've ever forgotten an interviewer's name during an important interview or been unable to remember basic math during a standardized test, you're certainly not alone. A number of studies show your brain's response to stress, while helpful if you're being attacked by a bear or fending off a burglar, isn't exactly the greatest when it comes to memory formation and retrieval.

    While a number of mechanisms may be responsible for the effects of stress on memory, one of the key players is a class of steroid hormones called glucocorticoids, more commonly known as cortisol. During stressful events, your body's adrenal glands pump out cortisol like there's no tomorrow. Although a certain amount of cortisol is normal and maybe even helpful, too much can prevent the formation of new memories or the retrieval of old ones. Cortisol also interferes with your brain's neurotransmitters, preventing communication between brain cells. Since memory is a team effort, having your brain's communication lines down is like having a single electric wire knocked down in a thunderstorm.

    Yet another side effect of all these stress hormones is the diversion of mass amounts of energy to exercising muscles. As previously mentioned, this is great if you need to outrun a massive bear, but it also means less energy is available to the brain's hippocampus, a key component in learning and memory. Without enough energy, the hippocampus has trouble forming new memories, perhaps explaining why many people who have experienced trauma can't recall the event.

    Sometimes the effect of stress on memory is only temporary -- the high levels of cortisol simply make memories inaccessible for a short period of time. But long-term stress can set off a cycle that's hard to stop. This is because sustained stress damages the hippocampus, which is responsible for telling the hypothalamus to stop releasing cortisol when it reaches a certain level. A damaged hippocampus can't tell the hypothalamus to cool it, so the cortisol keeps flowing, which in turn damages the hippocampus even more, which in turn … you get the idea. One study showed older people had lost 20 to 25 percent of the cells in their hippocampus [source: Franklin Institute].

    The bottom line: Be good to your hippocampus. Take yoga, meditate, do whatever you can to prevent the little things from getting to you. Because when they get to you, they also get to your memory.

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  2. Alcohol abuse can destroy brain tissue; information doesn't get absorbed easily into long-term memory, so learning takes longer. In addition, excessive drinking often causes disorientation or blackouts, periods of amnesia in which memories are prevented from forming. Smoking affects the brain differently than heavy drinking. As a result of continuous smoke inhalation, less oxygen reaches the brain, causing confusion and memory loss. Studies show that smokers score lower on standardized memory tests than nonsmokers.

    Stress also is tied to addiction and to memory loss of its own. So for some people, managing overuse of alcohol and tobacco also boils down to managing stress. Stressors such as work or unemployment, financial strain, child-care issues and interpersonal conflicts can increase likelihood of developing bad habits such as overeating, smoking and drinking too much. Many women report that stress makes it harder to quit smoking. Evidence now shows that stress not only affects some memory functions in our brains, but that it can disrupt chemical functions that normally would help with our self-control and decision making [Yale Stress Center].

    Although moderate stress can increase your adrenaline levels and keep you focused and alert, ongoing stress is detrimental. Stress releases glucocorticoid hormones, which aid brain function. But prolonged high levels of glucocorticoids can harm the hippocampus, the section of the brain responsible for explicit memories like facts and events. For example, you might not remember where you placed your car keys. Overexposure to glucocorticoids during a high-stress period can actually shrink the hippocampus, permanently inhibiting your ability to concentrate and access long-term memories. A Yale University professor isolated an enzyme that works on the neurons in the prefrontal cortex. Stress produces an abundance of these enzymes that break down the neurons, damaging the brain's emotional and impulse controls, along with the ability to think analytically [source: Boston].

    The good news is that unless you have chronic stress or anxiety, your brain can recover if you put a stop to the stress. Unfortunately, the long-term effects of smoking on the brain aren't necessarily reversible; quitting only halts any further damage [source: NeuroLogic].

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