(2) is often how heavy use of SSRIs presents.
Many Western countries average 0.3 pills a day per capita.
NPCs are mostly made, not born.
Discussion
Hmmmm
Messing with hormones and trauma during gestation (and early childhood) creates NPC-behavior, sudden violence, suicides, homosexuality, etc... in just about every animal model you can think of.
So, though not in your "nature", you can be born NPC and it might just be the most crucial determining period. Thank god humans are so adaptive and can regenerate in like one generation.