Warning: The following contains spoilers for Immortal Hulk #26 by Al Ewing, Joe Bennett, Ruy Jose, Paul Mounts, and VC's Cory Petit, on sale now.
The Hulk has always twisted the personality of the individual who transforms into the gamma-irradiated figure. But a new theory floated in the pages of Immortal Hulk suggest that mental instability might be more severe than anyone realized.
The mental problems behind all the Hulk transformations may be coming directly from Bruce Banner.
HULK SYNDROME, EXPLAINED
The issue is centered around the fallout of Bruce Banner releasing a manifesto video outlining his plans to bring down people who commit major global crimes in the name of profit. While Amadeus Cho is speaking with Bruce, he mentions something known as "Hulk Syndrome". The theory, as Doc Samson reveals to Doctor McGowan, is that because all of the gamma energy that's granted to people like She-Hulk, the energy may have taken some elements of Banner's psyche as well.
Banner was suffering from Dissociative Identity Disorder long before he became the Hulk, leading to figures in his mind that would later inform beings like the Hulk. The blast of gamma radiation that transformed him into the Hulk allowed the other parts of Banner's mind to break loose, taking over his body and mind. These are the various Hulk personas like Joe Fixit, Professor Hulk and the Green Scar. As Samson explains, the hypothesis behind "Hulk Syndrome" is that receiving powers from Banner brings elements of Dissociative Identity Disorder as well. This could be the explanation for changes to the personalities of those transformed by gamma energy.
This could also explain why people who become Hulks seem to have new personalities emerge. Cho believes this was the reason his own inner darkness took on the shape of the Hulk inside his mind, while Samson concedes that it would explain some of the personality changes recently seen in Jennifer Walters when she becomes the more fearsome and savage version of the She-Hulk in Avengers. Even Samson was briefly evil during the "Fall of the Hulks" event, his mind clouded and personality changed. It's a compelling theory and would suggest that the instability of being a Hulk is a consistently contagious ailment for people afflicted with these powers.
THE HULK'S VIRAL PERSONALITIES
Samson briefly mentions a more frightening idea though: Immortal Hulk has been exploring the connection between the Hulk and the One Below All, an all-powerful and monumentally evil being. It was connected to the Hulk in his moment of creation and has been trying to push him towards becoming a terrible and all-consuming beast known as the World-Breaker. Samson suggests that Banner might also be suffering from Hulk Syndrome on top of his earlier Dissociative Identity Disorder, which would mean that the major changes to his psyche over the years were made worse when he was infected by the gamma energy. If Banner's not the source of Hulk Syndrome, it could be connected to the One Below All instead. It could even be manipulating Banner to create a darker chain of events across the Marvel Universe.
This would not only mean that the One Below All is the being responsible for all the different Hulk personas over the years, but it would mean Banner has been spreading an infection connected to the One Below All to other heroes. Cho, Walters, and Samson might be susceptible to that evil as a result, all because of their connection to Bruce Banner. Banner might be unknowingly spreading the influence of the Marvel Universe's greatest evil, inadvertently becoming the threat he always tried to say he wasn't.