Thanks for using healthcare magic.
As far as head injury is concerned,as you do not have any neurological symptoms or residuals, it will not decrease your IQ.benzodiazepine
and alcohol both may impair your cognitive functions. So you should consult your psychiatrist
for detailed evaluation of anxiety.
Doctor may rule out physical causes of anxiety like thyroid dysfunction
. Doctor may also identify the type of anxiety or ther eason behind having anxiety if any.
Depending upon that, doctor may prescribe antidepressant drugs having anti anxiety properties like peroxetine or escitalopram or non benzodiazepine anxiolytic buspiron.
You may get benefit by doing stress management
and self relaxation therapy
like meditation or yoga.
I hope It will help you.