What are the leading causes of adult mental retardation? Possible causes in drop of IQ?

Published July 6, 2010

Question by student: What are the leading causes of adult mental retardation? Possible causes in drop of IQ?
What’re primary causes of retardation, IQ decrease, general stupidness?

Say a person started off very smart. Nature gives that person a lot of mental gift and brain power, what are some causes of retardation for adults? Could it be due to Chemcial inbalance? Substance abuse? Life style factors? Behavioral (OCD, masturbation, nervous habits, behavioral disorders)? Sex abuse? Mental illness? Physical illness? Stress? Depression? Toxins/poisons? Or what? What are signs to watch for for this mental challenges/changes in adults?

Best answer:

Answer by Empanada
A baseball bat to the head might have that effect.

What do you think? Answer below!