Capacity to consent to medical treatment in Australia

Before most medical treatment, a health professional needs your consent. For that consent to count, you need capacity to consent to medical treatment. That means being able to understand and weigh up the choice in front of you.

Most adults have this capacity. Illness, injury, dementia or a sudden crisis can affect it for some decisions. This guide explains what capacity means, who makes decisions when a person cannot, how the rules differ between states, and when a formal assessment can help.

What valid consent involves

Healthdirect explains that for consent to be valid, you need to:

• give it voluntarily, without being forced
• receive information about your condition and options, including the benefits and risks
• have the legal capacity to consent
• be able to communicate your decision.

Consent is needed for treatments and procedures, except in some emergencies. You can usually change your mind, and you can refuse treatment if you have capacity, even if others disagree.

What capacity to consent means

Capacity is about the decision-making process, not the choice itself. In Victoria, the Office of the Public Advocate (OPA) explains that a person has capacity for a medical decision if they can:

• understand the information relevant to the decision and its effect
• retain that information long enough to make the decision
• use or weigh that information in making the decision
• communicate the decision and their views in some way.

Other states use similar ideas, though the wording differs. Some principles apply across Australia:

• Capacity is presumed. Adults are presumed to have capacity unless there is evidence to the contrary.
• It is decision-specific. A person may be able to consent to a blood test but not to major surgery.
• Support counts. A person has capacity if they can decide with practicable and appropriate support, such as an interpreter, simpler explanations or extra time.
• It can change. Delirium, pain, sedation or intoxication may affect capacity for a while.

OPA notes it is the responsibility of the health practitioner to determine capacity for a specific decision. If the person is likely to regain capacity soon, the decision should usually wait, unless delay would risk a significant deterioration in their health.

Who decides when a person cannot consent

Each state and territory has its own law. Here is how three of the largest states handle it.

Victoria

The Medical Treatment Planning and Decisions Act 2016 began in March 2018. Health practitioners must follow a valid instructional directive in an advance care directive. If there is no directive for the decision, the medical treatment decision maker is the first person on this list who is reasonably available, willing and able:

1. a person the patient formally appointed
2. a guardian appointed by VCAT for medical decisions
3. the first of: a spouse or domestic partner, the primary unpaid carer, an adult child, a parent, or an adult sibling.

Compulsory mental health treatment sits under a separate law, the Mental Health and Wellbeing Act 2022.

New South Wales

Under the Guardianship Act 1987, consent comes from the “person responsible”. The NCAT fact sheet sets out the order: an appointed guardian or enduring guardian with medical powers, then a spouse or partner, then an unpaid carer, then a relative or friend. NCAT itself must consent to some special treatments, and can step in where there is no person responsible or the patient objects.

Queensland

Queensland’s laws include the Guardianship and Administration Act 2000 and the Powers of Attorney Act 1998. If you have not appointed anyone, a statutory health attorney can make most health decisions. This is the first available of a spouse or de facto partner, an unpaid primary carer, or a close friend or relative. The Public Guardian is the last resort.

Other states and territories have their own laws and terms. If you move interstate, check that your documents will be recognised.

Young people and consent

Healthdirect notes that parents or guardians usually consent for children, with some exceptions for young people. A young person under 18 may be able to consent if they have enough understanding and maturity to fully understand what is proposed. This is sometimes called being a “mature minor” or Gillick competent.

Rules vary by state. For example, NSW Health guidance says that for young people aged 14 or 15, their own consent may be sufficient, but a parent’s consent should also be sought unless the young person objects. For 16 and 17 year olds, their consent is sufficient in most cases.

When a formal capacity assessment helps

Most of the time, the treating doctor assesses capacity as part of normal care. A more detailed assessment by a neuropsychologist, psychiatrist or geriatrician can help when:

• the decision is serious, such as major surgery or refusing life-sustaining treatment
• the person has dementia, a brain injury, an intellectual disability or a serious mental illness
• capacity seems to come and go
• family members and the treating team disagree
• a tribunal application is likely.

A neuropsychologist (a psychologist who specialises in how the brain affects thinking) looks at the thinking skills the decision depends on, such as memory, reasoning and insight. They also talk through the actual treatment decision with the person.

For example, a person recovering from a brain injury might understand that an operation carries risks, but be unable to hold the information long enough to compare it with other options. Another person might score poorly on memory tests yet still explain clearly why they do not want a particular treatment. The assessment looks at how the person reasons about this decision, not only at test scores.

If you disagree with a decision

If you are worried about a capacity decision, start by talking with the treating team and asking how capacity was assessed. You can ask for a second opinion. If a disagreement cannot be resolved, tribunals such as VCAT and NCAT can deal with some disputes about medical decisions and substitute decision makers. Getting legal advice early can help.

Planning ahead while you can

You can make it easier for others to follow your wishes by:

• writing an advance care directive that records your values and any treatments you would refuse
• appointing a medical treatment decision maker, enduring guardian or health attorney, depending on your state
• talking with your family and doctors about what matters to you.

Advance Care Planning Australia runs a free national advisory line on 1300 208 582.

How Invictus Health can help

Our neuropsychologists provide capacity assessments for medical, financial, legal and lifestyle decisions. Where there are wider concerns about memory or thinking, a neuropsychology assessment may help. Neuropsychology reports are reviewed by Dr Judy Tang OAM.

We have assessment clinics in every state and territory, and no GP referral is needed for most assessments. Contact us to discuss your situation. This article is general information and is not legal advice or medical advice. Please speak with a qualified professional about your circumstances.