The Mental Health Act 2007 introduced a
single definition of mental disorder.
Before the introduction of this definition,
the 1983 Act required clinicians to place
patients subject to the Act into one of
four categories of mental disorder,
namely mental illness, mental impairment,
psychopathic disorder and severe mental
impairment. Some provisions in the 1983
Act did not apply to people in some of
these categories. This led to difficulties as
some mental disorders did not fall
obviously into any of the categories