Tardive dyskinesia (TD) _{^{[ rough translation 'late onset faulty movements' ]}} is a condition featuring involuntary repetitive body movements, which are caused by the long-term use of some anti-psychotic medications such as Haloperidol, Chlorpromazine, Risperidone and Metoclopramide.(which is also used as an anti-emetic).

These drugs - classed as 'typical anti-psychotics' - were developed in the 1950s to treatSchizophreniaplugin-autotooltip__plain plugin-autotooltip_bigSchizophrenia

"Schizophrenia is a mental disorder characterized by abnormal social behavior and failure to understand what is real. Common symptoms include false beliefs, unclear or confused thinking, auditory and visual hallucinations, reduced social engagement and emotional expression, and a lack of motivation.", and are dopamine-receptor blocking agents (also referred to as neuroleptics).

( Note that there is a long list of other drugs which have also been shown to cause TD, ref )

The condition was first described in 1957 - and was originally called 'paroxysmal dyskinesia'. It was frequently mis-diagnosed ; with medical practitioners wrongly assuming the repetitive movements were a symptom of psychiatric disorder - whereas in reality they were being caused as a side-effect of prescription drugs.

The symptoms typically appear after several months of medication use. They sometimes go after the drugs are withdrawn, but occasionally persist permanently. There is currently no explanation for any of these effects. There are at least five major theories, but none has general acceptance (see link below).

It's also not known why some people develop the condition and others do not. It's estimated that as many as 70% of patients taking 'typical anti-psychotics' long term (i.e. decades) develop symptoms of TD.

Further (technical) reading : Tremor Other Hyperkinetic Movements (N Y). 2013; 3: tre-03-161-4138-1.