The power of suggestion can be strong. I once read somewhere that the more a diver was told he would experience narcosis at so and so depth then it was more likely the diver reported symptoms of narcosis at that depth.
Captain, this is likely the study in question:
DAN Divers Alert Network : Anxiety: Is It A Contraindication to Diving?
"A simple thought or association can often start a chain reaction of thoughts:
"I have on too much weight — What if I sink too fast? — I could burst an eardrum — No one would be able to reach me in time — I could go to the bottom, and it drops to over 800 feet off the coral wall — I could be crushed — I’m going to drown — PANIC!"
"Interestingly, we can “talk ourselves into” feeling more anxious over a given situation. Expectation, negative imagery, worrying all can trick us into experiencing a situation more negatively than we should, usually before the situation is even encountered."
"Author Bret Gilliam described a 1965 study conducted by Tom Mount, a pioneer in U.S. cave diving, and Dr. Gilbert Milner. They studied the effects of “anticipated behavior modeling” with respect to perceived and observed (subjective vs. objective) effects and the probability of experiencing nitrogen narcosis."
"In this experiment, three groups of divers received information regarding the topic of nitrogen narcosis:
* Group 1 was told that there was a high probability of experiencing the effects of nitrogen narcosis — in fact, they were told that everyone experienced severe symptoms at 130 feet / 40 meters.
* Individuals in Group 2 were informed that there was such a state as nitrogen narcosis, but that this was relatively rare and only a few people experienced symptoms at depth.
* The final group received a lecture regarding the recognition of symptoms, risks and dangers, but were told that persons with a strong will were able to resist and / or overcome symptoms of narcosis."
"In test dives between 130 and 240 feet (40 and 73 meters), the group who expected to experience symptoms of narcosis actually experienced these symptoms with greater frequency and severity than did persons in the other groups."
I have found that diving for example the same wreck in up to 150 ft of cold darkish water produces varying amounts of narcosis depending on my state of mind, how recently I was diving, how well rested I am, how cold I am, etc. And if I've been diving all through the winter, then my first deep boat dive after the ice is gone is less likely to provide a strong narcosis than if I'd stayed out of the water from January to May.
