I'm no pharmacology expert like others like Mr B and I may make some technical mistakes (forgive me). I think barbs, benzos and booze all work on the same receptors, GABA receptors. Opiates work on my favourite receptors the mu, kappa and delta opiate receptors (mu being the most euphoric). I have always loved for both of these, GABA when I first found alcohol at a young age, and the opiate receptors when I found opiates.
They are both CNS depressants, maybe that's why they're similar to you? It could also be why Mr B stated with that link which I haven't had the time to read.