Although many researchers have brought evidence for a positive role that religion plays in health, others have shown that religious practices and experiences may be linked to mental illnesses of various kind (mood disorders, personality disorders, psychiatric disorders). In 2011, a team of psychiatrists, behavioral psychologists, neurologists and neuropsychiatristsfrom the Harvard Medical School published a research which suggested the development of a new diagnostic category of psychiatric disorders related to religious delusion and hyperreligiosity.

They compared the thought and behavior of the most important figures in the Bible (Abraham, Moses, Jesus Christ and Paul) with patients affected by mental disorders related to the psychotic spectrum using different clusters of disorders and diagnostic criteria (DSM-IV-TR), and concluded that these Biblical figures ~~may have had psychotic symptoms that contributed inspiration for their revelations~~, such as schizophrenia, schizoaffective disorder, manic depression, delusional disorder, delusions of grandeur, auditory-visual hallucinations, paranoia, Geschwind syndrome (Paul especially) and abnormal experiences associated with temporal lobe epilepsy (TLE).

In 1998–2000 Pole Leszek Nowak (born 1962) from Poznań authored a study in which, based on his own history of religious delusions of mission and overvalued ideas, and information communicated in the Gospels, made an attempt at reconstructing Jesus′ psyche with the view of Jesus as apocalyptic prophet. He does so in chapters containing, in sequence, an analysis of character traits of the ″savior of mankind″, a description of the possible course of events from the period of Jesus^^ public activity, a naturalistic explanation of miracles.