I'd go with a Confusion effect myself, except that half the results of the Confused condition involve attacking people, and while that might be appropriate for someone out of their head on PCP, LSD mostly incapacitates you, and isn't the sort of thing that drives one to violence. People on LSD get really introspective, disassociated, and sometimes have personality crises. Also, they dance in a really characteristic way that lets you spot the acid-heads at a party.
That's why I went with Fascinated instead of Confused. Less Helter-Skelter, more navel-gazing.