In Possession (1981) and The Brood (1979) demonic creatures, representing malicious and deranged psychological tendencies, grow as physical entities with the madness. Although these horror films use the creatures as a visual device to portray the horror of the mental states 1/5

2/5 ...and their impact on others, my reaction to the depiction of such states as being related to the influence of external entities is “this but unironically” Traditional cultures always attribute madness, delusion and the like to the influence of spirits, daemons etc...

3/5 ...20th c. psychologists argued madness is the result of traumatic experiences (nurture not nature) but behavioural genetics shows that all mental illness is influenced by genetics, even when related to a traumatic event. How you respond to trauma IS genetically determined...

4/5...The idea of daemons attached to families and people and determining resembles how science shows most traits, from personality to intelligence, are heritable. Whether genes or daemons determine which partners we choose to raise children with, the psychological states...

5/5...we experience precede our individual existences and determine much of how our life plays out.

Forgot to add that only The Brood deals with theme of heritability of mental illness, while Possession is more about the danger or moral relativity

Interesting that in Japan mental illness was seen as the result of the presence of akuma (often translated as devil or demon)