Full effects of Xanax includes: +250 Energy, +75 Happy, -35% to all fighting stats (for 360-480 minutes)
In chains, people stack multiple Xanax before (so they'll have like 650-1000 e)
Overdose is random - some people overdose after taking 1, some people can take it for a month before overdosing (faction/company (nightclub) specials can reduce this rate)