I suspect that the conflict (not "imbalance") between the hemispheres causes the anxiety related symptoms, the problems of SELF-CONTROL. What Anni experiences with the ball, PTSD sufferers experience constantly with the resembles of the trauma, feelings, thoughts, impulses, without a final decision. They totally lose control over themselves.
For example if you've been raped, when it happened, while it happened, your right brain fired the commands to your body to fight of flight at all costs, while the left brain simply saw that there's no chance to escape or fight, because the abuser was stronger, he'd have killed you, he's your father etc. That conflict can't be resolved, until you gain cognitive power over your rightish, strong instincts. You have to accept that the possibility of being raped is real.
If you don't accept it, you have to pay the price: the hemispheric conflict may cause anxiety problems (uncontrollable fear, panic, thoughts, feelings etc.), autism, ADHD, stuttering, ticking, epilepsy, ambidexterity, left-handedness, addictions etc. etc. etc. - because your natural brain functioning is upset, and you can't do important activities properly (stutterers for example use their right hemisphere to speak!).
That's why it helped LRS gaining leftish control over a previously rightish activity.