Mental Health and Writing a Will: Understanding Testamentary Capacity in Australia

If you or a loved one live with a mental health condition such as bipolar disorder, dementia, or depression, you may be wondering: Can I still make a valid Will? The answer is yes — in many cases, individuals with mental health conditions can legally write a Will, as long as they meet the legal requirements for testamentary capacity.

What Is Testamentary Capacity?

Testamentary capacity is the legal term for the mental ability required to make a valid Will. It ensures that the person making the Will (called the testator) understands:

• The nature and effect of making a Will,
• What assets and property they own, and
• Who might reasonably expect to benefit from their estate (e.g., family members, dependants).

This concept protects both the testator and their loved ones by ensuring that the Will reflects true, considered intentions.

Does Mental Illness Disqualify Someone from Making a Will?

Not necessarily. Having a mental health condition — such as bipolar disorder, schizophrenia, dementia, or depression — does not automatically mean a person lacks testamentary capacity. The key question is whether the illness has significantly impaired the person’s understanding and judgment when writing their Will.

How Is Capacity Assessed?

In most Australian jurisdictions, lawyers and courts use a functional test to determine testamentary capacity. The person must be able to:

1. Understand the nature and effect of making a Will,
2. Know the extent of their estate (what they own), and
3. Appreciate the claims of those who might reasonably expect to benefit from their estate.

If someone meets these criteria, even if they have a diagnosed mental health condition, they are legally able to make a Will.

What Role Do Medical Professionals Play?

A medical practitioner — often a general practitioner, geriatrician, or psychiatrist — can be asked to assess a person’s cognitive abilities and give an opinion about whether they have testamentary capacity. This can be especially helpful if the Will is later challenged in court. Importantly, this kind of assessment is different from assessing capacity for healthcare or financial decisions.

At MuslimWills, we encourage families to consider obtaining such an assessment if there are concerns about a loved one’s mental state.

Challenging a Will Based on Capacity

If a beneficiary or eligible person believes that the testator lacked capacity at the time of writing their Will, they may legally challenge it. The court will then consider:

• Medical evidence,
• Witness testimony,
• The presence of a prior valid Will, or
• If no Will exists, the rules of intestacy (how estates are distributed when there is no valid Will).

This is why it is so important for individuals with mental health conditions to write a Will while they are well and lucid, and to consider medical documentation as part of the process.

When Should You Seek Legal Advice?

If you are concerned that a loved one may not have full testamentary capacity, or if they are in early stages of a condition like dementia, it is best to:

• Act early while they still have clarity,
• Consult a legal professional, and
• Consider a formal medical assessment to support the validity of the Will.

Legal advice is essential if there’s a risk of disputes or family tension around the person’s estate.

Final Thoughts

A mental health condition does not disqualify someone from writing a Will — capacity depends on their ability to understand what they’re doing, not the diagnosis itself. If you’re unsure, it’s always best to seek legal guidance and proceed with compassion and clarity.