I should also add that Lindsey has said that he wasn't as much into cocaine as others. He just didn't say it in the context of why he left in 1987.
But yeah he's said it. He said he never bought cocaine himself, because it was too expensive. He said that he liked marijuana.
Mick and Stevie have also said that Lindsey didn't do cocaine as much as the rest of them.
Lindsey certainly admits to doing some drugs, though. In his solo shows he has long joked with Neale and Brett about not remembering much of the past, because they were all hurting themselves back then.