An example of this situation would be an individual who has a fear of mice but lives in an area without mice. Even though the concept of mice causes marked distress and impairment within the individual, because the individual does not usually encounter mice, no actual distress or impairment is ever experienced. It is recommended that proximity to, and ability to escape from, the stimulus also be considered. As the phobic person approaches a feared stimulus, anxiety levels increase, and the degree to which the person perceives they might escape from the stimulus affects the intensity of fear in instances such as riding an elevator (e.g. anxiety increases at the midway point between floors and decreases when the floor is reached and the doors open). The DSM-V has been updated to reflect that an individual may have changed their daily activities around the feared stimulus in such a way that they may avoid it altogether. The person may still meet criteria for the diagnosis if they continue to avoid or refuse to participate in activities they would involve possible exposure to the phobic stimulus. Specific phobias
A specific phobia is a marked and persistent fear of an object or situation. Specific phobias may also include fear of losing control, panicking, and fainting from an encounter with the phobia. Specific phobias are defined concerning objects or situations, whereas social phobias emphasize social fear and the evaluations that might accompany them. The DSM breaks specific phobias into five subtypes: animal, natural environment, blood-injection-injury, situational and other.
Mechanism
Limbic system
Beneath the lateral fissure in the cerebral cortex, the insula, or insular cortex, of the brain has been identified as part of the limbic system, along with the cingulated gyrus, hippocampus, corpus callosum, and other nearby cortices. This system has been found to play a role in emotion processing, and the insula, in particular, may contribute to maintaining autonomic functions. Studies by Critchley et al. indicate the insula as being involved in the experience of emotion by detecting and interpreting threatening stimuli. Similar studies monitoring insula activity have shown a correlation between increased insular activation and anxiety.In the frontal lobes, other cortices involved with phobia and fear are the anterior cingulate cortex and the medial prefrontal cortex. In the processing of emotional stimuli, studies on phobic reactions to facial expressions have indicated that these areas are involved in the processing and responding to negative stimuli. The ventromedial prefrontal cortex has been said to influence the amygdala by monitoring its reaction to emotional stimuli or even fearful memories. Most specifically, the medial prefrontal cortex is active during the extinction of fear and is responsible for long-term extinction. Stimulation of this area decreases conditioned fear responses, so its role may be in inhibiting the amygdala and its reaction to fearful stimuli.The hippocampus is a horseshoe-shaped structure that plays an essential part in the brains limbic system. This is because it forms memories and connects them with emotions and the senses.