Clinical and demographic associations of recorded feigning in functional neurological disorder.

Although functional neurological disorder (FND) is common, increasingly recognized, potentially disabling, and treatable, it remains stigmatized, and concerns about feigning persist among clinicians. We examined the prevalence of malingering and factitious disorder diagnoses in individuals with FND, their associated demographic and clinical characteristics, and evidence of clinician bias in the diagnosis of feigning. In this retrospective cohort and case-control study using the international TriNetX electronic health record network, we analysed diagnostic codes (International Classification of Diseases, Tenth Revision) for FND, malingering and factitious disorder to assess their prevalence and overlap. We then compared rates of malingering and factitious disorder following a diagnosis of FND with those in cohorts of patients with multiple sclerosis and with depression, used as comparison conditions. We also examined demographic characteristics and comorbidities of FND cases with and without records of feigning, as well as temporal trends in the proportion diagnosed with malingering. Between 2015 and 2024, 143 471 individuals were diagnosed with FND, 54 685 with malingering and 5215 with factitious disorder. 2.2% of individuals with FND also received a record of malingering or, less commonly, factitious disorder, or both. Following diagnosis, FND was associated with higher rates of malingering (1.36%) and factitious disorder (0.62%) compared to multiple sclerosis (0.17%, odds ratio 7.97, 95% confidence interval 7.17-8.87; and 0.03%, odds ratio 20.47, 95% confidence interval 16.15-25.94, respectively) and depression (0.42%, odds ratio 3.23, 95% confidence interval 3.08-3.39; and 0.05%, odds ratio 12.17, 95% confidence interval 11.18-13.31, respectively). Among FND cases, factitious disorder was more prevalent in White individuals, whereas malingering was more frequent in males, Black individuals and seizure presentations. Compared to other FND cases, those with diagnoses of malingering or factitious disorder had more psychiatric, neurological, and medical comorbidities, greater socio-economic adversity and increased mortality. Records of malingering were more likely in FND cases with histories of other stigmatized disorders, such as sexually transmitted diseases, viral hepatitis and HIV. Their proportion declined from 2018 to 2023. Malingering and factitious disorder are more frequently diagnosed in FND than in comparable disorders, although both remain uncommon. Their presence is associated with greater clinical complexity and poorer outcomes. Associations with ethnicity, socio-economic adversity and certain comorbidities suggest possible clinician bias, while declining malingering diagnoses in FND may reflect growing awareness among clinicians.