delusion is the sudden loss of judicial conscience or intellect for some time. It is not permanent. In most cases it occurs for a short time. However, in some cases it can be for an indefinite period of time. Head injuries , low blood flow to the brain , neurological problems , neurological disorders , various diseases such as tetanus, can cause high blood pressure. Note that a lot of times when talking to a friend or relative next to him, he suddenly says something contradictory and we laugh that "Kiri is delusional or not ?" This is not a delusion in reality. However, if someone really has a delusion, it is also caught in this way. Illusions , mental retardation and apathy are not the same thing.