The song you're thinking of is True Faith by New Order.
True Faith was released in 1987, and was the fourteenth single by British new wave/synthpop band, New Order. It's one of their most famous songs, alongside Blue Monday and Temptation, and was used in one of the nightclub scenes in American Psycho.
The general consensus is that the song is about drug abuse and/or dependency, a theory supported by the fact that the line "Now that we've grown up together, they're all taking drugs with me" was replaced with "They're afraid of what they see" (although the original line is still usually sung live). True Faith has been covered and remixed by many artists and bands since its release, including George Michael, Anberlin and The Boo Radleys.
About New Order
With the addition of Gillian Gilbert, New Order consists of the surviving members of Joy Division. After the suicide of Joy Division's singer Ian Curtis in early 1980, the band reformed as New Order, as they'd agreed that, if any member was to leave, the remaining members would continue under a different name. New Order went on to enjoy greater commercial success than the original band; however, Joy Division developed iconic cult status after Curtis' suicide.
You can listen to the song here: