Objective The illness perceptions of the relatives of patients with functional neurological symptom disorders (FNSD) and the relation to patients' illness perceptions have been little studied. We aimed to compare illness perceptions of relatives of patients with FNSD to those held by patients themselves. We used control pairs with neurological diseases (ND) to examine the specificity of the findings to FNSD.

Method Patients with FNSD (functional limb weakness and psychogenic non-epileptic seizures) and patients with ND causing limb weakness and epilepsy, and their relatives, completed adapted versions of the Illness Perception Questionnaire Revised (IPQ-R).

Results We included 112 pairs of patients with FNSD and their relatives and 60 ND patient and relative pairs. Relatives of patients with FNSD were more likely to endorse psychological explanations and, in particular stress as a causal factor than patients with FNSD (p<.001). Relatives of FNSD patients were also more pessimistic about the expected duration of the disorder and perceived a greater emotional impact than patients themselves (p><.001). However, the latter two differences between patients and relatives were also found in ND pairs.

Conclusion The main difference in illness perceptions between relatives and patients with FNSD was a tendency for relatives to see psychological factors as more relevant than patients. Some other differences were observed between FNSD relatives and patients but the same differences were also seen in ND pairs. These other differences were therefore not specific to FNSD. Discussion about possibly relevant psychological factors with patients suffering from FNSD may be helped by including relatives.