text: what kind of head trauma causes loss of intelligence?   almost any unresolved mental trauma will reduce the brain's ability to function. most people can remember only recent traumas, but these are often related to stuff that can be years old & lost to conscious memory, but the brain is still trying to deal with it.  think of it like your computer running a whole load of unnecessary software. it slows down performance. the difference with the brain is that anything similar to the unresolved issue goes straight into the "i can't handle it" area.  unresolved stuff still goes round in the memory & takes up capacity as the brain tries to come to terms with it. once you're able to face meories of the trauma without it causing fear, then it is resolved & will release memory capacity & function again.   counselling clients have completely changed as a result of resolving past traumas, childhood stuff often gets stuck there. i've seen a guy who had a 40 year old incident resolved & suddenly he could do normal stuff he'd only dreamed of.