Stress acts on various levels of our being, including the physiological, neurological, psychological, and social levels. All of these levels are interconnected and affect one another, influencing the overall state of one’s well-being. Our brain is the master controller that interprets what is stressful or not, and thus manages the physiological and behavioral responses suitable to that interpretation. An automatic alarm reaction is triggered throughout our body whenever a threat is identified. This reaction activates the body’s sympathetic nervous system, which controls the fight-flight-freeze response.

The fight-or-flight reaction is our body’s way of “clearing the decks” to face immediate danger with defensive or aggressive action. It does this by rapidly signaling a series of biochemical changes and nervous-system firings. Overall, we become more alert, attentive, and prepared to fight for our lives.

While the responses of fight or flight tend to be the most commonly recognized, there is a third physiological response to stress that we occasionally utilize, which has been termed as the freeze response.

When faced with an inescapable stressor, our body responds by releasing endogenous opioids (otherwise known as endorphins or our body’s natural morphine). These neurotransmitters have an analgesic effect and thus serve to numb pain–both physical and emotional–when death or harm seems inevitable. In humans, this response often manifests as dissociation, immobility, or “shutting down.”

While the brain is the manager of the stress response, it too can fall victim to its consequences. Researchers have found extensive evidence of how widespread the effects of stress are across various brain regions. For example, the limbic system, which plays a significant role in emotional processing, becomes activated when an individual is stressed to help the body process and prepare for a response. In cases of chronic stress, however, the prolonged activation of the limbic system may contribute to irrational decision-making and exaggerated emotional reactions to daily stressors. When a person feels threatened by a stressor the rapid limbic system reacts before the slower prefrontal cortex has a chance to evaluate the stimulus. Usually, the prefrontal cortex modulates limbic activity and helps to inhibit inappropriate responses, but extreme stress interrupts this usual flow so that the body can respond as quickly as possible, although the response may not be rational or well thought-out in the moment. Excessive stress hormones also impair the functioning of the prefrontal cortex. In situations of chronic or excessive stress, these hormones are overproduced and can cause physical harm. Exposure to large amounts of hormones can damage the central nervous system, hippocampus, and several other organs of the body. It can also age brain cells more rapidly, build fat around the body’s midsection, and cause learning deficits.