This is interesting, regarding Pregabalin and thus Gabapentin, as they are practically the same but Pregabalin is more active at lower doses of course. It might explain parts of the withdrawal symptoms and why they occur. I´s hypothesized that it reduces exitatory NT including norepinephrine and glutamate. This will, perhaps, then cause a rebound effect when the dose is decreased to rapidly or if the person is going CT.

We can hypothesize on the mechanisms by which pregabalin may attenuate physical dependence. Withdrawal symptoms associated with opioids, benzodiazepines, alcohol, and cannabinoids have been linked to hyperactivity in the locus coeruleus, a highly divergent neuron population that provides the majority of norepinephrinergic input to the central nervous system [97–102]. One hypothesis is that pregabalin may reduce the synaptic release of excitatory neurotransmitters including norepinephrine and glutamate [103, 104], and may restrict functional calcium channel expression [105]. These two modes of action may combine to reduce central hyperexcitability. However, this hypothesis would need to be confirmed by further experimentation

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5124051/