Definitions of terms within the Act

Apart from the broad definition of mental disorder, a specific diagnosis is not required for detention under Sections 2, 4 or 5. The Mental Health Act specifies four specific categories of mental disorder for detention under other sections of the 1983 Act; Mental Illness, Mental Impairment, Severe Mental Impairment & Psychopathic Disorder

Mental Illness
The Act does not define mental illness and leaves this as a matter for clinical judgement.
The Department of Health provided a guide to the symptoms associated with mental illness in the consultation document that came before the 1983 Act: mental illness means an illness having one or more of the following characteristics:

  • more than a temporary impairment of intellectual functions shown by a failure of memory, orientation, comprehension and learning capacity
  • more than a temporary alteration of mood of such a degree as to give rise to the patient having a delusional appraisal of his situation, his past or his future, or that of others or to the lack of any appraisal
  • delusional beliefs, persecutory, jealous or grandiose
  • abnormal perceptions associated with delusional misinterpretations of events
  • thinking so disordered as to prevent the patient making a reasonable appraisal of this situation or having reasonable communication with others
  • the mental illness should be of a nature or degree to warrant the detention of the patient in the interest of his health or safety or for the protection of others.

Mental Impairment
 means a state of mind (not amounting to severe mental impairment) which includes significant impairment of intelligence and social functioning and is associated with abnormally aggressive or seriously irresponsible conduct'

Severe Mental Impairment
means a state of arrested or incomplete development of mind which includes severe impairment of intelligence and social functioning and is associated with abnormally aggressive or seriously irresponsible conduct'

The distinction between severe mental impairment and mental impairment is one of degree. The assessment of the level of impairment is a matter for clinical judgement.

Psychopathic Disorder
 means a persistent disorder or disability of mind (whether or not including significant impairment of intelligence) which results in abnormally aggressive or seriously irresponsible conduct'

Treatability
 When a person is described as having a mental impairment or a psychopathic disorder the treatment sections of the act, Sections 3, 37, 47 and 48, can only be used when the doctors can confirm that the treatment the person will receive is likely to alleviate a deterioration of their condition.

Substance use and Mental Disorder
The phrase more than a temporary impairment of intellectual functions will exclude mental disorder that is caused by substance use and which ends when the substance passes out of the body, eg being drunk.