Malingering and factitious disorder.

Although exaggeration or amplification of symptoms is common in all illness, deliberate deception is rare. In settings associated with litigation/disability evaluation, the rate of malingering may be as high as 30%, but its frequency in clinical practice is not known. We describe the main characteristics of deliberate deception (factitious disorders and malingering) and ways that neurologists might detect symptom exaggeration. The key to establishing that the extent or severity of reported symptoms does not truly represent their severity is to elicit inconsistencies in different domains, but it is not possible to determine whether the reports are intentionally inaccurate. Neurological disorders where difficulty in determining the degree of willed exaggeration is most likely include functional weakness and movement disorders, post-concussional syndrome (or mild traumatic brain injury), psychogenic non-epileptic attacks and complex regional pain syndrome type 1 (especially when there is an associated functional movement disorder). Symptom amplification or even fabrication are more likely if the patient might gain benefit of some sort, not necessarily financial. Techniques to detect deception in medicolegal settings include covert surveillance and review of social media accounts. We also briefly describe specialised psychological tests designed to elicit effort from the patient. © Author(s) (or their employer(s)) 2019. No commercial re-use. See rights and permissions. Published by BMJ.