Using depressants can cause loss of coordination, slurred speech, confusion, and a slowed heart rate. these symptoms can lead to more serious consequences, such as
a. coma
b. bad grades
c. loss of trust
d. loss of friends

Such as A - coma.

A very extreme side effect or rather end effect of depressants can be, besides the mentioned loss of coordination, slurred speech, etc. also coma. 

This can happen in very extreme cases and also only in a small percentage. Coma as a side effect is usually (And of course) not desired.