From the book The Cybergypsies, by Indra Sinha - here he’s talking about life on the game Shades, an early MUD:

Jarly has tried many times to stop, to break his modem habit. He’s tried everything he can think of but, lying on his narrow bed, he knows that sooner or later he will succumb to the whispering of the little mouth in the wall. He describes to me the self-hatred and sweetness of the inevitable moment of surrender, of giving in, letting go, of busy fingers conjuring a fix, the buzz of the modem coming to life, the whistle of connection sliding like a needle into his brain, and the rush of relief as he floats into the game.

 ‘It isn’t like a drug. It is a fucking drug. The pleasure chemicals that happen when you do drugs, Bear? Well, the same fuckers are triggered by the modem.’