Fear is an incredibly strong emotion,if something scares us, the body immediately releases endorphins, dopamine, and norepinephrine. Endorphins alleviate pain, dopamine and norepinephrine are performance enhancers. There aren't any direct studies on extreme sports that I'm aware of, but the general scientific thinking is that the more fearful a certain sport makes you, the greater the release of these chemicals. The greater the release of these chemicals, the greater the addiction-like symptoms. Remember, the major component of crack (they won't let me say the name...jeezle) is considered the most addictive substance on earth and it does nothing more than flood the brain with dopamine. Norepinephrine, on the other hand, mimics the second most addictive substance around... methamphetamine. Our neuro-chemicals are not one to one matches for these substances either. In fact, they’re much more powerful. The most common, endorphin produced by the body is 100 times more powerful than morphine. Check out adrenalineaddicts dot org...
Yes after a while some people think they need it so they can function and do certain activities. If they take Adrenaline for a while they may gain that habit. The body gets used to the adrenaline as a source of energy and starts to depend on it. So when that person stops taking that adrenaline the body looses its source of energy and gets weak. They can get this addiction very quickly.
This is often the root cause of different addictions in the first place, a need for a quick rush. It's similar to how the enneagram personality type -- Type 7 -- or the Adventurer has the habit of trying to do fun things as much as possible, to distract themselves from the real problems and insecurities inside them.
To some people yes.