I remember, when I was taking 3 x the max dose on Benadryl,
and Unisom...I only started with 1, but tolerance grew,
and grew. I was not drinking or doing drugs at this point, but I was out of control on these things.
Anyway, one day I just decided it was enough, and never took another one since..about 4-1/2 years ago. It took me 6 weeks to back to normal sleeping.
So, to an extent, anything can be addictive if you abuse it for other than it's original purpose.