An increase in adrenaline causes one's heart and breathing to accelerate, muscles tighten and sweat glands to activate, it also triggers a release of stored sugar, increased metabolic rate and inhibited digestion. While it may have made sense for me to have this sort of reaction to spiders if I was living thousands of years ago, nowadays it makes my life more difficult. Although scientists are not sure as to exactly what causes phobias, many believe that they are caused by a combination of environmental and genetic factors. Phobia can be caused by a traumatic event- if someone almost drowns then they may develop a fear of water. Yet this would only explain certain kinds of specific phobias, and not social phobia or Agoraphobia.
Some therapists believe that phobias are learned, and can therefore be unlearned.
This theory is the basis for some treatment in which one is gradually exposed to the thing that she fears, forcing her to confront the fear and recognize that it is, in fact, not rational. With the invention of virtual reality, this type of therapy has become easier, because one does not have to actually ever leave the room to experience her phobia. It is not clear, however, whether this is as effective. Another way of treating phobias and other Anxiety disorders is to take medication. Seratonin re-uptake inhibitors such as Paxil or Luvox, which can also be used to treat clinical depression, are sometimes effective in curbing Anxiety disorders.