Demons are the spirits of the hybrids and nephilin, they are the spirits of every creature God did not created, like hybrids, offspring of the fallen angels, etc.
Most of the so called mind enfermities are demonic possessions or opressions. Depression, adction, anger, all of these are signs.
If your voice changes and you start saying things that you do not want, this is also a big sign.
The authority of Jesus Christ can cast out any demon, just use it.
This happened to me during puberty. Demon confirmed.