How common are religious delusions found among persons with psychotic disorders? Prevalence rates depend on the particular psychotic disorder and the location in the world where the person lives. In less religious areas of the world, for example, one study showed that only 7% of 324 Japanese inpatients had delusions of persecution and religious guilt (Tateyama et al., 1998). This rate is similar to those from a nation-wide study of hospitalized patients with schizophrenia in Japan involving 429 patients, where the prevalence of religious delusions was 11% (Kitamur et al., 1998).
In the United States, a number of studies have examined religious delusions in patients with schizophrenia or bipolar disorder. The first of these reported results of a small study of 41 psychotic patients in New York City, finding that 39% of those with schizophrenia and 22% of those with mania had religious delusions (Cothran & Harvey, 1986). In a much larger study of 1,136 psychiatric inpatients in the mid-western and eastern United States, 25% of patients with schizophrenia and 15% of those with bipolar disorder had religious delusions (Appelbaum et al., 1999). Compared to other delusions, religious delusions appeared to be held with greater conviction than other delusions. Finally, Getz and colleagues (2001) compared the frequency of religious delusions across religious denomination in 133 inpatients (74% schizophrenia) at the University of Cincinnati Medical Center. Religious delusions were documented in 24% of 33 non-religious patients, 43% of 71 Protestant patients, and 21% of 29 Catholic patients.
In Europe and Great Britain, one study of 251 inpatients with schizophrenia in Austria and Germany reported a prevalence rate of 21% for religious delusions (Tateyama et al., 1998). One of the most detailed studies to date from Great Britain found that 24% of 193 patients with schizophrenia had religious delusions (Siddle et al., 2002a). Patients with religious delusions had more severe hallucinations and bizarre delusions, had poorer functioning, a longer duration of illness, and were taking more anti-psychotic medication than other patients. Thus, in studies of patients with schizophrenia, religious delusions are present in 7-11% of Japanese patients, 21-24% of Western European patients, and 21-43% of patients in the United States.