The Martha Mitchell effect is the process by which a psychiatrist, psychologist, or other mental health clinician mistakes the patient's perception of real events as delusional and misdiagnoses accordingly.
According to Vaughan Bell, "Sometimes, improbable reports are erroneously assumed to be symptoms of mental illness," due to a "failure or inability to verify whether the events have actually taken place, no matter how improbable intuitively they might appear to the busy clinician."
Quoting psychotherapist Joseph Berke, the authors note that "even paranoids have enemies." Any patient, they explain, can be misdiagnosed by clinicians, especially ones with a history of paranoid delusions.
Psychologist Brendan Maher named the effect after Martha Beall Mitchell. Mrs. Mitchell was the wife of John Mitchell, Attorney-General in the Nixon administration. When she alleged that White House officials were engaged in illegal activities, her claims were attributed to mental illness. Ultimately, however, the relevant facts of the Watergate scandal vindicated her and hence attracted to her the title of 'Cassandra of Watergate'.
In late October 1991, I complained to senior managers at the law firm where I worked, Akin, Gump, Strauss, Hauer & Feld, that I believed I was a victim of harassment by coworkers and others at the firm. A few days later I was terminated. The firm said it had investigated my complaint and could not substantiate my claims. In a later legal proceedings, the firm alleged that it had contacted two "consultants" -- including the internationally known psychiatrist Gertrude R. Ticho, MD! -- who said that my belief system was a sign of delusional thinking and that I posed a risk of violent behavior. It was an instance of the "Martha Mitchell effect."