Cyber-sickness: What happens when you stick too much Cyberware in your body? You get sick. Sometimes real sick, other times it’s like a summer cold, but it’s almost omnipresent with a Essence of less than 1.0 and it get worse the less Essence you have remaining. The lesser degrees of it can be handled strictly with role playing the "summer cold" symptoms, but for the more drastic degrees we want a mechanic.

In basis if you have 1.0 Essence or higher you never need to make any rolls to avoid the effects. If, on the other hand, you are a more normal kind of guy in my Shadowrun games and have .0035 essence left, you’ve got problems.

For every full .2 essence under 1.0 that you have there is a single die rolled against a target number of 4, for every success there you have a +1 modifier to social skills die rolls if you do not remove them with a Willpower check with the same target number. That means that if you are about to roll any kind of social skills check you have the roll to worry about. As an example let’s take a guy with 0.15 essence remaining. He has to roll 4 dice against a target number 4 to determine how badly his twitching, or dead eyed stare or obvious cyber limb (or, heaven forbid, all of the above) bothers the person he is interacting with. Say he rolls a 4,2,1,5 on those dice. Two successes minus what ever he gets on a Will Power T#4 check are added to his target numbers for that check. Usually this won’t amount to much, but… �

Alphaware equal to ½ or more of the total essence use the person has decreases the penalty number suffered by 1, Betaware will decrease it by 2. Conversely if ½ or more is cheap or second hand Cyberware increase the penalty by 1, or by 2 if all of it is cheap or second hand stuff. Thus a guy with a ton of Betware would never have more than a +2 and usually nothing at all…meaning you really can’t tell he’s a near cyber-zombie most of the time. On the opposite side a guy who has loaded himself down with parts scavenged from corpses he created will sometimes have as much as a +6 modifier and as even if he has fractionally more essence, he really looks more the cyber-zombie part.

So then comes the question of why would the loss of essence affect your social rolls or make you insane? A person who has lost his legs in a car crash and has them replaced by mechanical ones in order to be able to walk again would hardly develop some manic symptoms but would be happy to be able to walk again. Some can cope with such and some not. That's why in CP2020 you had to roll it to reflect the difference of people being able to cope with it, but as in SR it's a constant, I see it more on the how much "flesh" there is left for the human soul to still hold in it's vessel.

On some other thread this was bit discussed on the matter of riggers. Rigger could have a some simple implants (don't have the books with me) and with fairly low essence cost they will become a car or a tank or a plane. That would mess up the mind so much more, would it not? Spend 10 years as a oiltanker vs. have your legs replaced because of injury... which has more negative effect? I'd say let people roleplay such cybernetic mental problems if they wish to do so. Some would without a doubt develop some megalomaniac symptoms if put into a superman's robotic body.

Thus my comment is, no, I wouldn't take such ruling into my games nor would be happy camper to play in a game with such rule

Yes, SR3 Basic Book, p. 93 says that roughly every -2 essence gives +1 to many social interaction tests