Siblings of nonaffective psychosis patients at increased risk for movement disorders
MedWire News: Results from a Dutch study show that the unaffected siblings of patients with nonaffective psychosis are at increased risk for movement disorders.
"Movement disorders such as dyskinesia and Parkinsonism (resting tremor, bradykinesia, rigidity, and postural instability) have been reported in patients with psychosis or schizophrenia since long before the introduction of antipsychotic medication and might possibly be regarded as one of the core features of the illness," explain Jeroen Koning (Psychiatric Centre Symfora Group, Amersfoort) and team.
"Furthermore, there is evidence that these hyper- and hypokinetic movement disorders also occur in populations that are at risk for schizophrenia or other nonaffective psychoses, such as adolescents with schizotypal symptoms, children of patients with schizophrenia, and first degree relatives of schizophrenia patients," they explain.
To investigate further, the team studied 42 nonpsychotic siblings of patients with nonaffective psychosis and 38 mentally healthy controls without a first- or second-degree relative with psychosis or schizophrenia.
All of the participants, who were aged between 18 and 45 years, were assessed for the presence of dyskinesia and Parkinsonism using the Abnormal Involuntary Movement Scale (AIMS), Guy, 1976 E. Guy, Abnormal Involuntary Movement Scale, ECDEU assessment manual for psychopharmacologyNational institute of mental Health, U.S. Department Health and Human Services (1976).and the Unified Parkinson Disease Rating Scale (UPDRS), respectively. They also underwent mechanical instrument measurement, which is considered more sensitive to subtle motor signs than observation-based clinical rating scales.
Using the clinical rating scales, the researchers found no significant differences between siblings and controls regarding the prevalence of dyskinesia (AIMS item score ≥2) and Parkinsonism (UPDRS item score ≥2), at 7% and 0% versus 3% and 0%, respectively.
However, using mechanical instrument measurement, the team found that siblings showed significantly more signs of dyskinesia and Parkinsonism than controls, at 21% and 30% versus 5% and 6%, respectively.
Koning and colleagues conclude: "Our study shows that movement disorders are significantly more prevalent in nonpsychotic siblings of patients with a nonaffective psychosis than in controls when measured with mechanical instruments, but not when assessed with clinical rating scales.
"This suggests that motor signs could be markers of vulnerability for psychosis or schizophrenia."
They add: "Since mechanical instrument measurement of movement disorders is more sensitive than assessment with clinical rating scales, it may be of value in screening programs for populations at risk for psychosis."
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By Mark Cowen