Since some people respond to drugs/alcohol/etc., clearly the altered response of many others does not tell us immediately what the root cause is. But I think we already have a pretty good but basic idea what the root cause is and how this corresponds to the change in reaction to alcohol and other drugs of many PFS patients.
The altered reaction or non-reaction to drugs/alcohol/etc. of many people here is probably related to altered neurosteroids. We know that our neurosteroid levels are significantly altered compared to a control group, e.g. allopregnanolone was pretty much undetectable in the PFS patient group. There is evidence that the intoxicating reaction to alcohol is related to an increase in neurosteroids, among others the aforementioned allopregnanolone. If you do not respond to alcohol, it’s probably because your allopregnanolone levels are too low. Ironically, Finasteride has been considered to treat alcoholism.
The root cause, however, is a couple of steps further down the chain. The question is, of course, why neurosteroid levels are altered. The neurosteroids in question are metabolised by 3a-HSD which is driven by AR gene expression. In the end, all PFS/PSSD/PAS symptoms can be linked to reduced AR gene expression. And AR gene expression is probably reduced as a result of a negative feedback loop driven by overexpressed AR.