I had disabling sciatica for a year and I thought a break from work would do me good; perhaps 3 months of exercise, no slouching over a computer, no deadlines, etc. would improve the situation. Nothing worked. In desperation, I consulted many, many specialists, even chiropractors, but nope, no change.

Alas, I had banked on _something_ changing in 3 months, so I had planned a walking holiday in Western Ireland (Dingle) before rejoining work. I wasn't prepared to cancel the tickets, so I went anyway. I took along a plywood board to help me sit angled on the seat to avoid having to sit at right angles!

Started the walk on The Dingle Way in a dubious frame of mind. I knew I was doing it only because I was too cheap to cancel tickets. Then magic happened. The place is so exquisitely beautiful that I walked 25 kms on the first day, even sharing a backpack with my wife. That evening, everything was hurting, but not in the usual places I had been conditioned to expect. The sciatica was GONE! I couldn't believe it, but it didn't recur the next morning. It has been 20 years now.

It is possible mine was a simple case that just required a structural realignment. But I had tried walking before, and many other strategies to improve posture etc. In hindsight, the only difference is that my brain in Ireland was fully engaged in the beauty of the place and people, and disengaged from the pain. Perhaps exercising my back without being focused on a cure is what worked. Who knows? Perhaps this anecdote is of some value to your friend.

Thank you, Ireland!

My situation was unusual, so I'm not sure my solutions would generalize. Sciatica in teens is very unusual. The cause, likely, was a series of fairly involved surgeries I had had as a young child combined with overuse. None of the orthopedists I saw were particularly sure about the cause, nor were the physical therapists.

The long term solution was to avoid triggers and increase core strength. The short term solution was NSAIDs and correcting sleep posture (getting an 8-9 hour reprieve from loading the muscles that spasm remains very helpful).

Long-distance running was a trigger for me (particularly running slowly, oddly enough), so I haven't run in basically a decade. I used to run 5 days a week. It was pretty clearly part of my identity.

Years later, I picked up rock climbing (2-3 days a week) and my problems incidentally went away. Whenever I stop climbing for a while, I get periodic minor flare-ups. Fortunately, the short term fixes can nip this in the bud, particularly if I start exercising again.

I don't know the details of their situation, but I would encourage them to seek out a physical therapist. And to change therapists if it doesn't work. It took me a while to find someone that could actually help. I have no idea why the first therapists did not suggest improving sleep posture.

Not the OP, but I also had sciatica as a teen. In my case, it was caused by a chair whose seat was not level; it tilted slightly to the side. It went on for a year or two, I think. Eventually I realized what the cause was, got rid of the chair, and the pain gradually got better until it went away completely.