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What is mental illness?

A mental illness is a medical condition where a person’s thought, mood, perception or memory is significantly disturbed. Some examples are:

  • depression
  • schizophrenia
  • anxiety disorders.

What is not mental illness?

A person is not mentally ill just because:

  • of their political, religious, philosophical activities or beliefs
  • of their sexual preference, gender identity or sexual orientation
  • they engage in illegal conduct
  • they engage in a certain pattern of sexual behaviour
  • they engange in conduct that is contrary to community standards of acceptable conduct’
  • they have an intellectual disability
  • they have an anti-social personality or behaviour
  • they belong to a particular economic, social, cultural or racial group
  • they have previously been treated for a mental illness
  • they are experiencing or have experienced psychological distress
  • they have previously been involved in family conflict.

A person is not described as being mentally ill just because they take drugs or alcohol. However, if a person's mind or body is seriously affected by taking drugs or alcohol this could be taken as a sign that they are mentally ill, whether the effect is permanent or temporary.

Note: People with intellectual disabilities are covered by the Victorian Disability Act 2006 (link below).

See s. 4(2)—Mental Health and Wellbeing Act 2022 (Vic)(opens in a new window).

Being diagnosed with a mental illness

Only a doctor can decide whether a person has a mental illness and only after a proper assessment. Once a person has been diagnosed with a mental illness they can be offered treatment.

Voluntary patients

A person with a mental illness can be treated as a 'voluntary' (or informal) patient.

Most people with a mental illness are treated voluntarily. A voluntary patient can be treated as an out-patient, either by their local general practitioner, a psychologist, a psychiatrist or seek treatment at a local community mental health centre. People can also be admitted to hospital as voluntary patients, but are free to refuse treatment and leave whenever they want.

Note: A psychologist is not a medical doctor and cannot prescribe medication.

Compulsory patients

A person with a mental illness can also be treated as a compulsory (involuntary) patient if certain criteria are met. This means they can be detained in hospital and treated against their will. They can also be treated as an involuntary patient in the community if they are subject to a community treatment order.

See Assessment process (being diagnosed with a mental illness)

More information


Mental Health and Wellbeing Act 2022 (Vic)

  • s. 4—Meaning of mental illness
  • s. 4(2)—behaviours that do not indicate that a person is mentally ill

See Mental Health and Wellbeing Act 2022 (Vic)(opens in a new window).

Disability Act 2006 (Vic)

  • s. 4—aims to reinforce the human rights of people in Victoria who have a disability
  • s. 6—applies specifically to people who have an intellectual disability

See Disability Act 2006 (Vic)(opens in a new window)