Well usually adolescence to young adulthood is when personality disorders actually develop....but usually there are factors that effected them growing up that lead to the personality disorder. Also though having a personality disorder is not the same thing as turning into a sociopathic monster, there are lots of different personality disorders and its mostly anti-social personality disorder that is associated with aggressive sort of behavior, then there is avoidant personality disorder where the person avoids a lot of things due to anxiety/insecurity feelings so it is kind of complex.
Also personality disorders do not stop once you get past your 30's they are usually more life-long, however people with them can sometimes get help with it and it can become less problematic for them....but that varies on individuals.
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