Help, what type of mental illness is it to think that everybody is against you?

Paranoid symptoms : Paranoid and persecutory thinking is primarily symptomatic of Psychotic disorders, but it also can be a manifestation of certain personality disorders such as paranoid and Borderline PD. it also can be a manifestation of Dementia with psychotic features good luck and feel better

Varies: Many psychotic disorders can cause persecutory paranoia, most commonly schizophrenia. Some severe forms of depression can be associated with similar paranoia. Some people's paranoia is a personality trait, some so severe that it qualifies as a personality disorder. All can benefit from treatment.