Hello
The collective unconscious is a huge subconscious ' reservoir ', straight fed by the instincts ( reproduction, instinct of self-preservation..Etc...) It contains the entirety of subconscious emotions. It allows the personality to be unified, via some important symbols.
The collective unconscious is never sick too. Why ? Because it is impersonal, it is not a part of the individual experience. The repressions, inhibitions, complexes etc.. are never in it so, but are in the personal unconscious.
The collective unconscious is formed by the psychic images, they are as an alive sediment / deposit. We can say the collective unconscious is a ' superior ' unconscious. It is a mental heritage common with the whole manking.
Thus of all human eternity, the ' deep life ' is stayed the same, regardless of the ethnicity / race, religion, intelligence.
Our collective unconscious manifests itself to us across the archetypals and the symbols. ( our dreams are made by symbols). An archetypal is a condensed emotion that lives in the collectif unconscious.
Carl Jung has enormously studied the collective unconscious.
Catherine
( sorry for my bad english, but I hope I helped)