It's different from suicide, because at least in that one, you're looking to die. Here, you've got Joe Normal working on an elevator, then falling for one minute knowing he's going to die.
To be a bit morbid, suicides will probably have fluctuating thoughts about whether to carry out their end-game actions or not. It's hard to say[1], but likely that a significant proportion of jumpers get past the "go/no go" uncertainty, make the jump and then while they are falling swing back to the other opinion. Especially with the rush of adreniline and suchlike that they must be experiencing.[2]
Now, assuming that a (properly applied) bullet to the head destroys consciousness (possibly even before any significant amount of the pain gets properly 'experienced'), there's no second thoughts to be had.
Overdoses could be either. At some point you could find yourself past the point of being able to physically accomplish anything yet still awake enough to realise you're heading into the unknown and able to reconsider things. Or (with a properly chosen set of pharmaceuticals) maybe you're beyond caring before even the LD50 point.
Sorry, depressing subject. I honestly don't have any tendencies that way (despite life not being
particularly fun at the moment), so I'm no reflecting any serious considerations on my part. And as I tend not to believe in an afterlife/God/etc I'm rather against people dying by their own hands or by other avoidable means, due to the complete loss of a personality from the world. (Not to mention that if there
is some kind of Eternal Judgement, most of the interpretations of such Ineffable Wills tend to suggest they frown on those that take their own lives and relegate them to the less nice suburbs of the hereafter.)
[1] I know of a friend-of-a-friend who lept from a building and landed on wooden 'veranda'-like structure instead of the concreted ground they undoubtedly were aiming for. "Why did I do it?" was (something like) the comment they made to the ambulance crew who had the hopeless task of caring for them while their broken body slowly gave up on them, but it's hard to say if that's a comment on the action or on the way they ended up causing themselves prolonged agony instead of (if you'll forgive the way I put it) just ending in the "splat!".
[2] I was knocked off my bike when I was young. I remember (or remember remembering, which might not be the same thing) being on my ballistic track through the air and extensively wondering if spreading my arms would let me
actually fly. That was a fraction of a second of realtime, before I hit the ground and rolled (my main injury was from my glancing contact with the car's bumper, having swerved to avoid most of the mass of the vehicle that pulled out in front of me) but far, far longer in consciousness.