Family studies not only indicate a strong genetic influence in the development of anxiety disorders, but also support the current classification system used by the DSM-IV. There is a high rate of panic disorder and depression among the families of individuals with panic disorder, leading to the conclusions that some individuals inherit a genetic predisposition to panic disorder, and that panic disorder and depression share some etiological considerations. Furthermore, family studies indicate that there is an increased risk that specific types of anxiety disorders will be genetically transmitted. This means that if there is a history of generalized social phobia in a family, an individual has a greater chance of inheriting social phobia (but not any other type of anxiety disorder). OCD is the only form of anxiety disorder where there is a predisposition to inherit an anxiety disorder and not OCD specifically. Twin studies indicate that anxiety disorders are moderately heritable. Although the concordance rates of monozygotic twins were higher than that of dizygotics, the numbers were relatively low, except for agoraphobia. The evidence from twin studies point to several interesting conclusions concerning the genetic risk for anxiety disorders. The genetic risk factors for these disorders are neither highly specific nor non-specific; one genetic factor was found which associated generalized anxiety disorder with depression, and another associated panic disorder with social phobias.

Finally, not only do unique environmental factors play a role in the etiology of these disorders, but also some environmental risk factors were specific to certain disorders. Neurological studies have found that there is increased activity in the anterior portion of the temporal lobe, an area associated with fear and emotions, in individuals suffering from panic disorder. Similar studies have also found that some patients with panic disorder also exhibit dysfunctions in the regulation of their norepinephrine system--but these results are mixed. Hormonal shifts, such as in the production of estrogen and progesterone, seem to play a role in the strength of the expression of OCD. There may also be a genetic link between Tourette's syndrome and OCD, and OCD and trichotillomania. Lastly, PET scan studies have discovered an over-activity of cingulum bundles, associated with the severity of the disorder, in the orbital prefrontal cortex. Support for this comes from the fact that symptoms can be alleviated through a surgical procedure known as cingulotomy, which destroys the axons connecting the prefrontal and cingulate cortex with the limbic cortex of the temporal lobe.