It might not be ONE thing that caused your adrenal fatigue. Stress is cumulative.
If you are a chronic worrier, who exercises excessively, who plays a lot of video games, who looks at p 0 r n o g r a p h y frequently, who has anger issues, who has an inability to rest or relax, who stays up late at night, etc, etc.......
it all adds up. Throw in a couple of serious infections, or severe pain from injury.....and you are on this forum ;)
Maybe your friends that drank coffee are more laid back, not type-A people, didn't work out excessively, etc.