Robin, your thought are interesting. I would point out to you, however, that AS can develop in childhood. I know I was showing early signs by the time I was 14. I ate an extremely healthy diet, was active and young. And at the chiropractor for the pain in my back. Other members here developed it at a younger age, as well. It is genetic, don't forget, and tends to run in families. As does the Crohn's Disease that I also live with. Both come down my mother's line, AS on on her father's side and Crohn's on her mother's side.
I do think there is a gut link involved, but I could hardly have been showing signs of that at age 14. When I say 'healthy' I mean 'uber-healthy'. No refined anything, very small amounts of red meat, lots of fresh veg and fruit, no cakes, no cookies, no potato chips, no candy, no pies, unless it was a special occasion. There was no 'trigger' for my Crohn's as there were aspects of that that I experienced as a young child (recognised in hind sight, which we all know is 20/20); although I did slip on black ice when I was twelve and landed on my tailbone, which I've often wondered was the trigger for the AS.
As to ibuprofen ... again, in my own case, I was not using high levels of pain killers of any kind as a child and young adult. That didn't start on a regular basis until I was in my late thirties. Not that I didn't need them; just didn't take them on a regular basis. I already had both Crohn's and AS fully blown by the time I was in my early 20s, but it flared then backed off. As a student of performance and dance, I injured myself all the time. I put my pain down to that. You have to be taking a lot of ibuprofen for quite some time for the gut to be impacted. I am sorry to hear that you feel it triggered your psoriasis. It can happen that way, I've read.
Considering that the ratio of male cases to female cases of AS is about 7:5 at this point, I'm wondering about your comment on pregnancy -- I do realise you were having a bit of a joke, but it indicates that you think pregnancy is a trigger? It might be for some, I suppose. But I've never been pregnant, so it doesn't apply to all.
And there is my cautionary note. Your case of AS, its progression, its triggers, is yours - nobody else's. Sadly, my triggers cannot be 'removed'. The AS and Crohn's are with me to stay. I have never achieved full remission, despite everything I've done to help myself. Some people do. Perhaps you will be one of those and I hope so.
Love and light.