Fear is a human emotion that is triggered by a perceived threat. It is a basic survival mechanism that signals our bodies to respond to danger with a fight or flight response. As such, it is an essential part of keeping us safe.
However, people who live in constant fear, whether from physical dangers in their environment or threats they perceive, can become incapacitated.
Fear prepares us to react to danger. Once we sense a potential danger, our body releases hormones that slow or shut down functions not needed for survival (such as our digestive system) and sharpen functions that might help us survive (such as eyesight). Our heart rate increases, and blood flows to muscles so we can run faster. Our body also increases the flow of hormones to an area of the brain known as the amygdala to help us focus on the presenting danger and store it in our memory.
Once the fear pathways are ramped up, the brain short-circuits more rational processing paths and reacts immediately to signals from the amygdala. When in this overactive state, the brain perceives events as negative and remembers them that way.
It also stores all the details surrounding the danger—the sights, sounds, odors, time of day, weather, and so forth. These memories tend to be very durable, although they may also be fragmented.
Later, the sights, sounds, and other contextual details of the event can become stimuli themselves and trigger fear. They may bring back the memory of the fearful event, or they may cause us to feel afraid without consciously knowing why. Because these cues were associated with previous danger, the brain may see them as a predictor of threat. This often happens with post-traumatic stress disorder (PSTD). For example, a soldier who experienced a bombing on a foggy day might find himself panicking when the weather turns foggy—without knowing why.
Fear can impair formation of long-term memories and cause damage to certain parts of the brain, such as the hippocampus. This can make it even more difficult to regulate fear and can leave a person anxious  most of the time. To someone in chronic fear, the world looks scary and their memories confirm that.
Moreover, fear can interrupt processes in our brains that allow us to regulate emotions, read non-verbal cues and other information presented to us, reflect before acting, and act ethically. This impacts our thinking and decision-making in negative ways, leaving us susceptible to intense emotions and impulsive reactions. All of these effects can leave us unable to act appropriately.
Other consequences of long-term fear include fatigue, clinical depression , accelerated ageing, and even premature death.
So whether threats to our security are real or perceived, they impact our mental and physical wellbeing .