You feel fear when you anticipate harm or danger from something, or as a reaction to a specific event. This emotion triggers the brain to issue a warning signal when danger approaches. The feeling of fear is activated through one of the senses (hearing, sight, touch, or smell). The nerves connected to that sense send a signal to a brain region called the thalamus, which then relays the signal to the amygdala.
The amygdala responds by releasing neurotransmitters made of chemicals called glutamate. These transmitters send signals to two other brain regions. The first is the periaqueductal gray, which is responsible for the automatic reactions such as freezing or jumping when scared—reactions that are hard to control. The second is the hypothalamus, which activates the autonomic nervous system and prepares the body for the “fight or flight” response. This leads to the adrenal glands releasing the hormones adrenaline and cortisol, which raise heart rate, blood pressure, and other symptoms associated with fear.
Fear causes automatic physiological changes. For instance, your heart rate and breathing speed increase, and in some cases, fear leads to shortness of breath. Blood vessels expand to send more oxygen to vital organs, and blood is pumped to the muscles to prepare them to act. Goosebumps—tiny hairs standing upright—are another clear sign of the body’s reaction to fear.
Your body also stores up energy, increasing glucose levels in the blood, as well as levels of calcium and white blood cells. Here are some effects of fear, especially when it is chronic or pathological:
Fear doesn’t only affect your body—it has a significant impact on your mental health as well. Over time, it becomes more difficult to regulate and cope with fear. This results in constant, unjustified worry and tension.
Fear also interferes with how emotions are processed in the brain, leading to poor decision-making and irrational behaviors. It heightens emotional reactions and, over the long term, can contribute to psychological disorders like depression, post-traumatic stress disorder (PTSD), and anxiety disorders.
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