According to Bell et al., "Sometimes, improbable reports are erroneously assumed to be symptoms of mental illness (Maher, 1998)", 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". Examples of such situations are: * Pursuit by organized criminals * Surveillance by law enforcement officers * Infidelity by a spouse * Physical issues Quoting psychotherapist Joseph Berke, the authors report that, "even paranoids have enemies". Delusions are "abnormal beliefs" and may be bizarre (considered impossible to be true), or non-bizarre (possible, but considered by the clinician as highly improbable). Beliefs about being poisoned, followed, marital infidelity or a conspiracy in the workplace are examples of non-bizarre beliefs that may be considered delusions. Any patient can be misdiagnosed by clinicians, especially patients with a history of paranoid delusions. Patients may be diagnosed as delusional when their grievances concern health care workers and/or health care institutions, even when the patient has no history of delusion. "A patient arriving claiming to have been injured by another health care professional is regarded as a crazy person who potentially could ruin the career of an innocent colleague."
Martha Mitchell effect
Bouba/kiki effect
Hook effect
Baskerville effect
Whitten effect
Ceiling effect 
Roseto effect
Flynn effect