People who rape are mentally ill or psychotic
For decades, a commonly accepted myth has been that all rapists are psychotic, insane, or otherwise mentally ill. Similar to the myth that only "bad"women are raped, the belief that all rapists are mentally ill provides a false sense of security that "normal" people cannot commit such atrocious crimes. The vast majority of rapes are committed by people who do not suffer from a severe mental illness. In one of the most comprehensive studies analyzing psychiatric diagnoses of 535 rapists from a Swedish prison, it was determined that only 2.6% suffered a personality disorder and only 1.7% were deemed clinically psychotic (Langstrom, Sjostedt & Grann, 2004).
Despite these findings, there is a tendency, especially in the U.S. among forensic mental-health specialists, to use the residual, paraphilia-not-otherwise-specified (PNOS) diagnosis in assessing and recommending treatment for convicted rapists. Given that a psychiatric diagnosis is required for civil commitment of rapists, such residual diagnoses have been used to detain rapists beyond their sentences (Frances, Sreenivasan & Weinberger, 2008). A great deal of controversy surrounds the notion of "inventing diagnoses" as a basis for further confining rapists when the research does not support it (Zander, 2008).