Hypnosis had become quite popular in attempting to treat many psychological conditions. I don’t think anyone really understood what they were dealing with, or how it worked, but the results looked promising. Unfortunately it was a time bomb waiting to go bang.
For millennia farmers had practiced selective breeding to shape the plants and animals to better suit their needs. Then science came up with genetic engineering to achieve better results faster. It seems to be working.
Dissociative identity disorder is difficult to treat, often taking 8 to 16 years to achieve results. So some therapists came up with a new treatment in which they used hypnosis to directly access the subconscious mind and rearrange it to suit their needs. Unfortunately their method had side effects.