Akathisia, or acathisia, is a syndrome characterized by unpleasant sensations of "inner" restlessness that manifests itself with an inability to sit still or remain motionless (hence the word's origin in Ancient Greek: from καθίζειν - kathízein - "to sit" with a privative a as prefix expressing negation or absence; literally meaning inability to sit).
Akathisia may range in intensity from a sense of disquiet or anxiety, to severe discomfort, particularly in the knees. Patients typically pace for hours because the pressure on the knees reduces the discomfort slightly; once their knees become fatigued, they sit or lie down.
High-functioning patients have described the feeling as a sense of inner tension and torment or chemical torture.
Jack Henry Abbot (1981),a convicted murderer and author, described the effects of akathisia produced by antipsychotic drugs when given without the necessary medication for side effects (e.g. procyclidine) as may occur in prison and even sometimes hospitals:
These drugs, in this family, do not calm or sedate the nerves. They attack. They attack from so deep inside you, you cannot locate the source of the pain ... The muscles of your jawbone go berserk, so that you bite the inside of your mouth and your jaw locks and the pain throbs. For hours every day this will occur. Your spinal column stiffens so that you can hardly move your head or your neck and sometimes your back bends like a bow and you cannot stand up. The pain grinds into your fiber ... You ache with restlessness, so you feel you have to walk, to pace. And then as soon as you start pacing, the opposite occurs to you; you must sit and rest. Back and forth, up and down you go in pain you cannot locate, in such wretched anxiety you are overwhelmed, because you cannot get relief even in breathing.
—Jack Henry Abbot, In the Belly of the Beast (1981/1991). Vintage Books, 35–36. Quoted in Robert Whitaker, Mad in America (2002, ISBN 0-7382-0799-3), 187.