Psychiatric outcome in patients with a psychogenic movement disorder: a prospective study.

OBJECTIVE: To assess psychiatric outcome in patients with an established diagnosis of a hyperkinetic (i.e. tremor, dystonia, myoclonus) psychogenic movement disorder.
BACKGROUND: Longitudinal studies of patients with psychogenic movement disorders (PMD) have to date suffered from small sample size, lack of sample homogeneity (psychogenic movements grouped with other somatoform disorders, mixed hyper and hypokinetic movements), the absence of structured psychiatric interviews, and a failure to adequately address the extent of psychiatric co-morbidity by adopting a hierarchical approach to diagnosis.
METHODS: A sample of 88 patients with documented PMD according to the criteria of Fahn and Williams were followed up on average 3.2 years (sd = 2.2; range 1-7 years) after first being assessed at a tertiary referral clinic for patients with movement disorders. The detailed psychiatric assessment included the Structured Clinical Interview for Axis (SCID-I) and Axis II (SCID-II) DSM-IV disorders which generated diagnoses with respect to major mental illness (SCID-I) and personality disorders (SCID-II) respectively.
RESULTS: Of 88 subjects initially seen in clinic, three had died (one by suicide), two were in nursing homes (Alzheimers disease, terminal cancer) and three had emigrated. Of the remaining 80 subjects, 42 (52.5%) agreed to be interviewed. There were no demographic or illness-related differences between those who agreed or refused participation. At follow-up, the mean age of subjects was 48.6 (13.3) years, 62.7% were female and 75% were unemployed. An Axis I diagnosis of mental illness was made in 40 (95.3%) subjects. The PMD had remitted in four subjects, but had been replaced in two of them by a different mental disorder. Thirty-eight percent of subjects with PMD had developed additional unexplained medical symptoms at follow-up. Point and lifetime prevalence rates for other Axis I diagnoses were: major depression 19.1% and 42.9%; anxiety disorders 38.2% and 61.9%; co-morbid major depression and anxiety disorders 11.9% and 28.6%. Personality disorders were present in 45% of the sample. No subject viewed their PMD as primarily psychiatric in origin. Poor outcome with respect to the abnormal movements was associated with long duration of symptoms, insidious onset of movements and psychiatric co-morbidity on Axis I diagnoses.
CONCLUSIONS: Follow-up data of patients with PMD revealed a persistence in abnormal movements in more than 90% of subjects. Prevalence rates of mental illness in excess of those found in the general population and in neurologic disorders plus an inability to acknowledge the essentially psychologic nature of their condition characterized the outcome picture and carries a poor longer term prognosis.