Demon Possession --
unclean spirits = evil spirits = demons
demon oppression = demon possession
That evening at sundown they brought to him all who were sick or oppressed by demons. And the whole city was gathered together at the door. And he healed many who were sick with various diseases, and cast out many demons. And he would not permit the demons to speak, because they knew him.
And the scribes who came down from Jerusalem were saying, “He is possessed by Beelzebul,” and “by the prince of demons he casts out the demons.”
Disabling spirits may be a type of evil spirit
Demons are spiritual parasites, forces that feed off of the spirits of the living, whether human or animal (remember Legion?)
Note the similarity between a person with Parkinson's Disease and the woman in Luke 13:11-13:
And behold, there was a woman who had had a disabling spirit for eighteen years. She was bent over and could not fully straighten herself.
When Jesus saw her, he called her over and said to her, 'Woman, you are freed from your disability.' And he laid his hands on her, and immediately she was made straight, and she glorified God.