Is dissociative identity disorder hereditary? My mother has never been diagnosed, but she has wild mood swings, does things that she later denies even when others witnessed them, gets into serious financial trouble (but doesn't seem to care), frequently threatens to kill herself, etc. She will NOT seek help, and she is so irrational that most of our family (including myself) have felt it unfortunately necessary to cut ourselves off from her. This all developed suddenly after the death of her mother five years ago. Meanwhile, I have been battling depression, insomnia, anxiety and mood swings, and plan to seek help. I'm worried that I may have the same problem. Will I have to worry about my son?

K.M.

The exact mechanisms by which people develop dissociative identity disorder (DID), formerly known as multiple personality disorder (MPD), are still under debate. Most understand DID to begin developing in childhood as a way of coping with severe abuse and neglect. While the disorder has been reported sometimes to "run in families," so to speak, that may be due to the repetition of intergenerational patterns of abuse and neglect, coupled with children's modeling their perspectives on self and identity after that of their dissociative parent(s), rather than true genetically based heredity. (Not all DID parents abuse their children, but even a nonabusive DID parent who switches to different aspects of self -- or alters -- frequently in the presence of his or her children might inadvertently teach the children a dissociated model of identity.)

Some clinicians speculate that people may inherit susceptibility to dissociation -- that is, some people may be naturally more "gifted" at dissociating than others -- but that DID develops in people with this capability only if they are subjected to severe abuse and neglect as children. That viewpoint suggests that people without the hypothesized susceptibility to dissociation who are severely abused or neglected might develop conditions other than DID, such as schizophrenia. (This is not to say, however, that all people with schizophrenia have abuse histories.) And people who inherit an hypothesized susceptibility to dissociation who are NOT abused might grow up to have great imaginations, or to be easily absorbed in fantasy. This perspective on an inherent dissociative ability is related to the observation that some people seem to naturally be more easily hypnotizable than others. But not all people with DID are what are called "excellent hypnotic subjects," even though dissociation has sometimes been described as a spontaneous trance state.

I'm glad you're seeking help for both your sake and your son's, but that doesn't necessarily mean you and he are destined to be diagnosed as DID, even if that's what your mother has. (By the way, it's not uncommon for someone with DID to not exhibit many of the symptoms in adulthood -- if they're in a relatively safe environment -- until they experience overwhelming stressors which trigger old wounds and dissociative coping strategies. The death or illness of a parent -- particularly a formerly abusive parent -- can certainly set off such reactions.)

Your best bet is to see a psychologist or other therapist who is experienced in the assessment and treatment of dissociative disorders as well as other conditions, which means he or she will be able to fully evaluate what you might be experiencing. As you may know, some clinicians claim they don't "believe" in DID or MPD, as if such conditions were a matter of faith rather than observation. Sometimes I suspect such clinicians erroneously believe accepting the DID diagnosis means accepting that a person actually has more than one personality. But that's not true; clinicians experienced in treating DID don't believe their clients have more than one personality -- but they understand that THE CLIENT believes that. The experienced therapist views the DID individual as having only one personality, but a fragmented one.

You ask whether you should worry about your son. If he was not abused or neglected as a child or raised by someone with dissociated aspects of self (whether your mother or yourself, if either of you fit that bill), I wouldn't think he'd develop DID. If you want to be sure, consider talking with your own therapist about having him evaluated. One thing's for sure, though -- your son is lucky to have a mother who's concerned about her own and his welfare and is willing to seek help. I wish that had been the same in your case.