Overactive Crown & 3rd Eye Chakra
When you have an overactive Sahasrara/Crown chakra and Ajna chakra/ 3rd eye you become susceptible to sickness of the mind. This is why spiritual gifts are often written off as mental illness. They can easily spiral out of control if you don't have the proper skill to ground yourself in reality. For example...
People with an overactive Crown chakra often experience existential despair. These people may have psychotics breaks and dissociate, or experience dissociative seizures if the mind is unable to handle the sheer vastness of the universal energies flowing in. If you have experienced having an overactive Sahasrara you may have "delusions of grandeur" ; a "chosen one" complex, a sense of being separately and uniquely "special" or uniquely "enlightened".
The Ajna Chakra is a little different as it governs intuition, perception, and inner vision that gives you the discernment to see beyond illusion. When overactive it causes a sort of psychic flux to occur, or abnormal discharge in other words. So your intuition is running wild hungry cheetahs. This will quickly cause one to become overwhelmed, with mental overactivity, from constant stimulation. The lines between intuition and delusion become indistinguishable, which can get even more tricky if you're someone who trusts yourself more than anyone else. You will become overwhelmed by visions which you'll need to proper wisdom to interpret. People with an overactive 3rd eye may also become very paranoid. Unseen energies, sylphs, and hidden truths are everywhere, but you may start to see them in places they are not.
