John Medina's Brain Rules

Entry 025: Of Allergies and Personalities

Timmy is NOT allergic to orange juice.

I know that sounds boring, but if you knew Timmy, you might find this fact anything but anodyne.

Timmy suffers from something that used to be called Multiple Personality Disorder. It’s now termed DID, short for Dissociative Identity Disorder, a condition where separate “personalities” appear to inhabit a single individual. Timmy’s case is famous. He was even mentioned in an old New York Times article. At the time of newspaper’s publication (1988), Timmy had a dozen other residents claiming squatting rights to his brain.

And some of them WERE allergic to orange juice.

If one of these sensitive personalities muscled his way to the main stage of Timmy’s brain, then drank the beverage, the skin became reddened and swollen and the body developed fluid-filled hives. This is good old contact dermatitis, a classic immune response to orange juice.

But that’s not the whole story. If Timmy’s non-allergenic personality somehow bumped one of these allergic strangers off the cognitive stage, the hives would disappear. So would the itching and the redness. Incredibly, the body Timmy time-shared with his other personalities was no longer allergic to orange juice. You could toggle poor Timmy’s shared immune system on and off like a light switch.

This has some truly staggering implications. It appears the brain, under the right circumstances, can selectively control major components of your immune response.

OUR NEXT SERIES

We are about to embark on another strange voyage atop the Brain Rules ocean. Our topic concerns the ability of the brain to exert “forces” over certain processes we had no idea it was capable of controlling. We will explore territory ranging from familiar placebo effects to less familiar somatic symptom disorders. The strange symptomology of DID is a great example of the direction we’re going.

Perhaps a few details about the disorder are worth exploring as we set sail.

The research world characterizes Dissociative Identity Disorder this way:

“The main diagnostic criterion for DID is the perceived presence of two or more distinct identities, accompanied by a marked discontinuity in the sense of self and agency, and alterations in affect, behavior, consciousness, memory, perception, cognition, and/or sensory-motor functioning.”

You should know that DID is controversial in some quarters. Objections range from the perceived sloppiness of the diagnostic description to an outright dismissal of the phenomenon. It hasn’t helped much that the entertainment media got involved, making movies like the Oscar-winning Three Faces of Eve and the Emmy-winning TV mini-series Sybil.

Controversy notwithstanding, the distress associated with legitimate DID is agonizingly real. People who experience the disorder have usually suffered severe child abuse, and they are susceptible to self-injury and suicide. Indeed, one of the hallmark characteristics of DID is its heartbreaking mortality rate.

Dear Readers, there is SO much we don’t know about how these brains of ours work. Timmy makes a useful starting point for this series, but we obviously have a great deal more to discuss.

REFERENCES

Goleman, D. "Probing the Enigma of Multiple Personality." New York Times https://www.nytimes.com/1988/06/28/science/probing-the-enigma-of-multiple-personality.html (1988).

Utomo, Y.P. et al. "Understanding Dissociative Identity Disorder: A Literature Review." Arch Psych Res 59, no. 2 (2023): 305-10.

Bachrach, N. et al. "Schema Therapy for Dissociative Identity Disorder: A Case Report." Fron Psych 14 (2023): doi.org/10.3389/fpsyt.2023.115187