Psychiatric outcome in patients with a psychogenic movement disorder

Objective: To assess psychiatric outcome in patients with an established di agnosis of a hyperkinetic (i.e. tremor, dystonia, myoclonus) psychogenic mo vement disorder. Background: Longitudinal studies of patients with psychoge nic movement disorders (PMD) have to date suffered from small sample size, lack of sample homogeneity (psychogenic movements grouped with other somato form disorders, mixed hyper and hypokinetic movements), the absence of stru ctured psychiatric interviews, and a failure to adequately address the exte nt of psychiatric co-morbidity by adopting a hierarchical approach to diagn osis. 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 cli nic for patients with movement disorders. The detailed psychiatric assessme nt 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 su icide), 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 betw een those who agreed or refused participation. At follow-up, the mean age o f 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. Th e PMD had remitted in four subjects, but had been replaced in two of them b y a different mental disorder. Thirty-eight percent of subjects with PMD ha d developed additional unexplained medical symptoms at follow-up. Point and lifetime prevalence rates for other Axis I diagnoses were: major depressio n 19.1% and 42.9%; anxiety disorders 38.2% and 61.9%; co-morbid major depre ssion and anxiety disorders 11.9% and 28.6%. Personality disorders were pre sent in 45% of the sample. No subject viewed their PMD as primarily psychia tric in origin. Poor outcome with respect to the abnormal movements was ass ociated with long duration of symptoms, insidious onset of movements and ps ychiatric 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 fou nd in the general population and in neurologic disorders plus an inability to acknowledge the essentially psychologic nature of their condition charac terized the outcome picture and carries a poor longer term prognosis.