Some of the primary explanations of anxiety include biological and neurobiological theories, which explore genetic and physiological factors that may contribute to anxiety and anxiety-related disorders. In contrast, behavioral and cognitive theories consider possible environmental factors that may precipitate the emotion.
Scientific studies have shown that feelings of anxiety are accompanied by physiological activity, also known as arousal, in a person's sympathetic nervous system. This activity or arousal, when moderate, may cause an individual to feel physical tenseness, nervousness or restlessness.
Research into the biology of anxiety has shown that certain parts of the brain, such as the amygdala in the temporal lobe, become activated when an individual experiences anxiety. The health of neurotransmitters, as well, can influence to what extent a person feels anxious or fearful.
Behavioral and cognitive scientists have found that environmental factors can also contribute to the experience of anxiety. For example, more than 70 percent of clinically diagnosed anxiety and panic disorders have been linked to severely stressful life experiences.
While a moderate feeling of anxiety can help a person to prepare for potential problems and to evade possible dangers, a strong feeling of anxiety can sometimes become debilitating. Studies have shown that individuals who experience extreme anxiety have greater difficulty dealing with potentially threatening situations.
Most people experience anxiety as an emotion triggered by the anticipation of potential danger. How and why people experience anxiety, though, is still a matter of debate among psychologists and scientists. Many theories exist as to the contributing factors and primary effects of anxiety, as well as the relationship between everyday anxiety and clinically diagnosed anxiety disorders.