No, it's not another drug he's taken. There is no exaggerating to it; protracted benzo withdrawal can affect many people for years after they quit taking them. The benzodiazepines actually rewire your neurons and it can take a long time to get it back to normal. It's science now that we know the withdrawal can take years, or rather,the reconstruction of your brain. Flumazenil can help supposedly.
Protracted withdrawal is no exaggeration,it's accepted as a very horrible thing.