Cause & Development
From an evolutionary point of view, the “fight-or-flight” dichotomy suggests that both hostility & avoidance are naturally occurring responses to fear. Both are thought to be based on anxiety evoked by the presence of a feared stimulus object or situation. However, avoidance can co-vary with fear, vary inversely or vary independently (Rachman & Hodgson, 1974). Therefore, avoidance behavior seems to be more complex than ís accountable for by the simple presence of fear or anxiety. What appear to be purposeful hostile reactions to others, for example, may be indicative of highly complex psychological processes.
It ís commonly believed that biological factors, including heredity & prenatal maternal factors, set the foundation for personality & personality disorders, while environmental factors shape the form of their expression (Millon & Everly). In the case of avoidant personality disorder, the evidence of major biogenic influences ín íts etiology & development ís speculative & weak (Millon & Everly). However, there ís some evidence that a timid temperament ín infancy may predispose individuals to developing APD later ín life (Kaplan & Sadock, 1991). While shyness appears to indicate underactivity, Kagan believes that this inherited tendency to be shy ís actually the result of overstimulation or an excess of incoming information. Timid individuals cannot cope with the excess of information & so withdraw from the situation as a self-protective measure. The inability to cope with this information overload may be due to a low autonomic arousal threshold (Venebles, 1968). The same mechanism may also be responsible for the avoidant’s hypervigilence. However, ít ís generally believed that these biological substrates exist within the avoidant personality as a biological foundation for the emergence of the disorder itself & that full development of APD ís likely due to significant environmental influences (Millon & Everly).

As the individual gets older there are fewer mandatory (like school) activities that will force them to engage in the world. Their social connectedness can become more and more limited. Their avoidance behaviors can have severe consequences on their social and occupational functioning.