Mixed-methods analysis of formulations in functional neurological disorder

Functional Neurological Disorder (FND) is a relatively common neuropsychiatric condition characterised by disabling or distressing, but potentially reversible, neurological symptoms. There are no well-validated treatments, despite emerging evidence for several psychotherapies. A formulation is a set of explanatory hypotheses answering the question ‘why does this patient suffer from this problem at this time?’ This study examined the formulations of adults with FND who were treated with Shared Individual Formulation Therapy (SIFT). SIFT uses clinical history-taking and hypothesis-refinement over several sessions to collaboratively formulate how symptoms have emerged in the context of the patient’s life experience, to identify relevant vulnerabilities and coping strategies. A shared individual formulation is co-written and verified with each participant to ensure it represents their experience accurately. Our objective was to explore the patterns and associations in these formulations. We extracted the formulations from twenty-four letters generated during a prospective, open-label trial of SIFT for FND. Framework analysis was used to identify the key features (‘exposures’, ‘schemas’, ‘activations’ and ‘mechanisms’) within each formulation. Subgroups identified using hierarchical clustering were compared statistically across characteristics, therapy ratings and outcome scores. Three clusters were identified. Two were characterised by overvigilance and body focus ( n = 10), and one was characterised by dissociation and other directedness ( n = 14). There was some indication of possible differences in treatment response, but numbers were too small to draw firm conclusions. Findings support the psychological heterogeneity of adults with FND. Analysis of formulations can be used to identify clinically distinct subgroups.