or the side effects of antipsychotic medication. The patient may have tics (involuntary but quasi-purposeful movements or vocalizations) which may be a symptom of Tourette's syndrome. There are a range of abnormalities of movement which are typical of catatonia, such as echopraxia, catalepsy, waxy flexibility and paratonia (or gegenhalten). Stereotypies (repetitive purposeless movements such as rocking or head banging) or mannerisms (repetitive quasi-purposeful abnormal movements such as a gesture or abnormal gait) may be a feature of chronic schizophrenia or autism. More global behavioural abnormalities may be noted, such as an increase in arousal and movement (described as psychomotor agitation or hyperactivity) which might reflect mania or delirium. An inability to sit still might represent akathisia, a side effect of antipsychotic medication. Similarly, a global decrease in arousal and movement (described as psychomotor retardation, akinesia or stupor) might indicate depression or a medical condition such as Parkinson's disease, dementia or delirium. The examiner would also comment on eye movements (repeatedly glancing to one side can suggest that the patient is experiencing hallucinations), and the quality of eye contact (which can provide clues to the patient's emotional state). Lack of eye contact may suggest depression or autism. Mood and affect The distinction between mood and affect in the MSE is subject to some disagreement. For example, Trzepacz and Baker (1993) describe affect as "the external and dynamic manifestations of a person's internal emotional state" and mood as "a person's predominant internal state at any one time", whereas Sims (1995) refers to affect as "differentiated specific feelings" and mood as "a more prolonged state or disposition". This article will use the Trzepacz and Baker (1993) definitions, with mood regarded as a current subjective state as described by the patient, and affect as the examiner's inferences of the quality of the patient's emotional state based on objective observation. Mood is described using the patient's own words, and can also be described in summary terms such as neutral, euthymic, dysphoric, euphoric, angry, anxious or apathetic. Alexithymic individuals may be unable to describe their subjective mood state. An individual who is unable to experience any pleasure may have anhedonia. Affect is described by labelling the apparent emotion conveyed by the person's nonverbal behavior (anxious, sad etc.), and also by using the parameters of appropriateness, intensity, range, reactivity and mobility. Affect may be described as appropriate or inappropriate to the current situation, and as congruent or