My best guess would be worms since that is the most common although most doctors don't think so. Your panic attacks could be from anything but I'm just letting you know that parasites(worms) have the ability to cause a panic attack. They can attack the Central Nervous System and create a number of different problems, panic attacks being one of them. Panic attacks can also be psychological so don't be giving yourself panic attacks because now you think you have worms!
When parasites feel threatened by something like Wormwood they won't go down without a fight. Attacking the Central Nervous System is on way of them fighting for their life.