I normally don't comment on these drugs/medical threads, but I've had patients on high doses of gabapentin, with side effects.

On the issue of gabapentin and dementia, here's a full study:

https://pmc.ncbi.nlm.nih.gov/articles/PMC10266423/

Here's a quick summary of another study on gabapentin and dementia:

https://rapm.bmj.com/content/early/2025/07/02/rapm-2025-106577

One thing I've noticed that doctors don't seem to advise patients enough about is that one of the potential side effects of gabapentin, especially at higher dosages, is suicidal ideation. I've run into two patients with such ideations after being prescribed  higher dosages for gabapentin for neurogenic (nerve-based) pain.