In this Act:
"mental illness" means a condition that seriously impairs (either temporarily or permanently) the mental functioning of a person in 1 or more areas of thought, mood, volition, perception, orientation or memory, and is characterised by—
(a) the presence of at least 1 of the following symptoms:
(i) delusions;
(ii) hallucinations;
(iii) serious disorders of streams of thought;
(iv) serious disorders of thought form;
(v) serious disturbance of mood; or
(b) sustained or repeated irrational behaviour that may be taken to indicate the presence of at least 1 of the symptoms mentioned in paragraph (a).