It's certainly helped me.
I've had a bit of a fear of heights for many years now, which I first experienced the first time I went up to the top of the Eiffel Tower nearly 30 years ago when I was in my late teens on a college trip. Since then it got gradually worse to the point where just climbing up a ladder would make me feel quite nervous. Anything where I felt "at risk" of falling or anything like that. It got quite irrational, fearing that buildings might suddenly collapse or the balcony I was stood on might suddenly break away from the building etc. I remember about 10 years ago going up the Spinnaker Tower in Portsmouth thinking that it wouldn't be so bad, and when I got to the top the height just hit me. It felt as if the ground was tilting up to face me. Very weird and super stress inducing, having to try and suppress panic attacks. Flying hasn't been too bad for me as I'd got used to that. Although where I hadn't flown for a few years back in my early 20's, by the time I went up again when I was about 30, the first few flights were quite stressful for me. Now my main problem with flying is the often cramped conditions.
Anyway onto VR. My first time in VR was using my mates Vive (even though I'd had my Rift on pre-order for ages by that time), and scenes in VR with heights just sent my stress levels soaring. I could stand there and consciously tell myself that it wasn't real and that I was standing in my mates livingroom, but my brain just wasn't having it. The flight or fight instincts kicked in as did the panic and fear responses and it made my first few times in VR very stressful and exhausting. I remember things like the menu section in Call of Starseed where you're stood up on this floating rock above a sort of void like space, I found just reaching out to use the menu screen near the edge of the platform really hard to do. As for Windlands, wow! That was just crazy! To my credit I got as far as getting the grapples and got across to two little islands but couldn't get to the next check point as by that time my nerves were just frazzled.
I think the more you use VR the more you brain gets used to the idea that this space isn't actually real or a threat to you, and so that impact begins to gradually lessen quite considerably. Which in some ways is a bit of a shame as the whole VR experience now feels less real to me than it did when I first used it. When I first got my Rift, things like that Batman style city scape in the Dream Deck where you're stood at the top of that skyscraper, were still very vertigo inducing. I kept going back to it though and exposing myself to it a bit at a time and also I found that experiencing it seated made me feel much more safer, comfortable and grounded in a way that standing didn't. I also got Windlands and started to play that seated and got used to it. Some of the heights and jumps in Windlands are still quite heartstopping, but I'm kind of glad of that, as in away I think that's part of the game. Subnautica, oddly I never had a problem with. I think that's because you're submerged in water and so there's no fear of falling because you're floating in a fluid. Adrift was quite acro and agoraphobia inducing, but again, the more I played it the more I became used to it and began to enjoy the vast views and the feeling of floating in space above the Earth.
Now in VR, practically nothing like that fazes me anymore. In real life too my fear of heights has much improved as a consequence. On a holiday to Malta last year, I was quite happily going out onto the small balcony of my hotel room several floors up and looking out over the edge of it and from the roof top bar and pool area, looking down to the street below and the sea front. I certainly would not have felt comfortable doing that previously. I definitely feel a lot more confident with heights now than I did before, that's for sure, and I have no doubt that exposure to heights in the safe environment of VR has helped me with that.
All of which kind of makes me feel that after playing Doom 3 in VR, that with a bit of body armour and a pump action shotgun, I'll be ready to take on the demonic hordes should a hellgate ever open here on Earth.