Both dissociative disorders and somatoform disorders involve a type of dissociation or detachment, wherein there are breakdowns in the functioning of normal mental processes of memory and consciousness. Both of these disorders were once viewed as forms of hysteria, wherein the uterus of the individual (who is frustrated with sexual desires, especially the desire to have a child) dislocates, causing problems in its new location. New speculation about the etiology of these disorders was later offered by Sigmund Freud and Pierre Janet. Both Freud and Janet believed that the dissociation between emotional conflicts and physical symptoms was caused by an initial traumatic event that required unconscious coping mechanisms in addition to normal coping efforts. Janet viewed this disassociation as an abnormal process, whilst Freud, who used the term synonymously with repression, did not. Freud later went even further, saying that these unconscious coping mechanisms were a defense against unacceptable id, or unconscious, impulses.

Questions concerning the epidemiology of dissociative disorders center on the concept that these disorders, since they are so culture-specific, may indicate the presence of a Western popular trend. Others, such as Nicholas Spanos, are skeptical, seeing these disorders as a type of role-play between the individual and the therapist. Studies tend to give conflicting evidence concerning the existence of these disorders because of the lack of information available about them and therefore a greater chance of misdiagnosis.

Except for hypochondriasis, which is equally common across genders, somatoform disorders are more common among females than males. These disorders are also more prevalent among the poor and uneducated, African- Americans, and individuals who have recently lost a spouse through separation, divorce, or death. Again, although we know that these disorders are rare, exact figures are difficult to ascertain due to the great probability of misdiagnosis of these disorders. Hypochondriasis and somatization disorders have both been found to be especially comorbid with depression and with anxiety disorders. Possible explanations of these links indicate that both somatoform disorders and depression may be caused by a third variable, such as a stressful or traumatic event. Similarly, both anxiety disorders and somatoform disorders share common defining categories. Evidence also indicates that somatization disorder may be the female version or expression of antisocial personality disorder.