SherkSilver's planner reckons Stimulant only has Hold, Immobilise, Sleep and Disorient/Stun, i.e. the usual four.
However I'm not sure it's 100% correct - while I was levelling my EM/Elec with a friend's SS/Elec brute we both had Stimulant as pre-req for Aid Self and I recall us using it on each other before engaging succubus bosses, so I have a feeling it has Confusion protection as well.
I'll have to check the next time I log-in.
I recently dusted off my necro/dark, trying a few sirens call missions to get back in the swing. Sheesh! those longbow just hit my poor zombies with multiple grenades and send them flying all over the room like puppets in a hurricane (maybe not grenades, but some sort of kb aoe). Does stimulant have KB protection? Given how often longbow turn up later in the game it would be well worth taking.
My MA IDs:
Fiend Space: 211464