opiods - possibly.
benzodiazepines - definitely.
How long have your sleep sessions become ever since you started abusing these drugs? The longest time I slept for before drugs used to be 7-8 hours straight. Now it's more like as low as 1 hour to as much as 4 hours tops and sometimes 5 hours if I've been slaving at work. Are you getting rest when you're asleep? Also, when you blackout or OD you don't dream. So you might be mistaking acute overdose or blackouts with sleep. Tonight before bed try to drink some warm milk but not for its sedative effect like many think. Dairy products before bed will make your stomach work overtime while you're asleep digesting and generally results in nightmares. So to test if your lack of dreams is physical or psychological eat a lot or drink milk right before bed. Another suggestion is to kick up your activity level especially if you've been slacking off just to see if it changes your dreamless dilemma. Just because you may be an addict doesn't mean you can't be a functional addict. These are just stabs in the dark, hope it helps. Good luck, man.
P/S/ If you're not an addict then forgive me for saying so.