Epidemiology and risk factors for (tardive) dyskinesia.

Dyskinesia can develop in patients with schizophrenia in the course of the disease with or without the use of antipsychotics.In patients with psychiatric disorders other than schizophrenia Tardive Dyskinesia (TD) can develop in patients treated with antipsychotics or other drugs with dopamine D2 blocking properties. Spontaneous Dyskinesia in antipsychotic naive patients with schizophrenia ranges from 4 to 40%, depending on the age and duration of the illness. Moreover, siblings of patients with schizophrenia have higher prevalence rates of dyskinesia than matched controls. Incidence rates of TD due to dopamine blocking properties vary due to the sample population and the affinity for the dopamine blocker to the D2 dopamine receptor. Once developed, TD seems very persistent, the course of TD might be mediated by the affinity for the dopamine D2 receptor. Risk factors for TD in the literature are numerous, in this chapter only replicated and risk factors from longitudinal studies will be reported limiting the amount of risk factors. Furthermore only meta-analyses on genetic factors related to TD will be discussed due to inconsistency of genetic effects because of sample heterogeneity, small effects of multiple genes, (epi)genetic interactions,pleiotropy and small sample size. Finally the concept "Tardive Dyskinesia" will be discussed and the influence hereof on the above mentioned factors.