Does Dementia Mean Someone Lacks Mental Capacity?

No. A dementia diagnosis on its own never proves someone lacks capacity, and the law is explicit about this. Capacity is assessed decision by decision, not diagnosis by diagnosis, and a person can have dementia while still having full capacity to make many of their own choices. The same goes for decisions others see as unwise. Making a choice that worries the family is not, in itself, evidence that someone cannot think it through.

In this post:

• Why a diagnosis and a capacity assessment are two different things
• Why an “unwise” decision is protected, not proof of incapacity
• How fluctuating capacity is managed in real assessments
• How I structure an assessment to protect rights and stand up to scrutiny
• What happens next if capacity genuinely is in doubt

Families come to me at some of the hardest points in a relative’s life, often after a diagnosis has just landed and everyone is trying to work out what it means for the decisions ahead. Two assumptions come up in nearly every conversation I have. The first is that a diagnosis of dementia settles the question of capacity. The second is that if someone makes a choice the family disagrees with, that choice must be the illness talking. Neither is true, and getting this wrong early on tends to cause more harm than the situation it was meant to prevent.

A Diagnosis Is Not a Capacity Assessment

Dementia affects people unevenly. Someone in the early stages of vascular dementia might struggle to manage a bank account but still be entirely capable of deciding where they want to live. Someone with more advanced dementia might lose the ability to weigh up a complex financial decision while retaining a clear, consistent view on their day to day care.

The Mental Capacity Act 2005 treats capacity as specific to the decision and the moment it is being made. A person is assumed to have capacity unless it is shown, through a proper assessment, that they do not. This presumption exists precisely because conditions like dementia do not remove capacity evenly or all at once.

I have carried out COP3 assessments (a standard form used to record a formal capacity assessment, often for the Court of Protection) where a person could not safely manage a large sum of money but could talk through the pros and cons of moving nearer their daughter with real clarity. Both findings came from the same visit. Treating a diagnosis as a blanket answer misses that nuance entirely, and it can strip someone of decisions they are still perfectly able to make.

“Ashley carried out the Mental Capacity Assessment with great care, clarity and respect. His approach was compassionate yet precise, which gave us real confidence in the reliability of the report.”
Inna Marston

An Unwise Decision Is Not Evidence of Incapacity

The right to make a decision other people think is a bad idea is written into the Mental Capacity Act. A person with full capacity can refuse a hospital admission, give money to a relative the family distrusts, or choose to stay in a home that others consider unsafe. None of that, by itself, says anything about whether they have capacity.

What matters is whether they understand the information relevant to the decision, can hold onto it long enough to use it, can weigh it against the alternatives, and can communicate what they’ve decided. If someone can do all four, the decision is theirs, however much it worries the people around them.

In my experience, families rarely raise a capacity question because they doubt someone’s thinking. They raise it because they are frightened for their relative and want a way to intervene. That instinct is understandable, but using a capacity assessment to override a choice someone is entitled to make sits outside what the law allows, and a properly conducted assessment will say so.

Capacity Can Change From One Day to the Next

Capacity is not fixed. Infections, fatigue, pain, medication changes and time of day can all affect how someone presents, particularly with dementia. Someone who cannot follow a conversation at 4pm after a difficult day might manage the same conversation clearly the next morning.

This is why a single bad afternoon should never be treated as the final word. Good practice means assessing the decision at the point it actually needs to be made, and where possible, giving someone the best chance to engage with it: the right time of day, a familiar environment, enough breaks, information presented simply.

Where capacity fluctuates significantly, I record that pattern rather than treating one snapshot as definitive. A decision made on someone’s worst day is not necessarily the decision that reflects their actual capacity, and a robust assessment has to account for that rather than paper over it.

How I Structure an Assessment to Respect Both Rights and Risk

Every assessment I carry out starts from the presumption that the person has capacity for the decision in question. My job is to test that, not assume the opposite and go looking for confirmation.

I use the two-stage test set out in the Act: first, whether there is an impairment of the mind or brain, and second, whether that impairment means the person cannot understand, retain, weigh up or communicate a decision about this specific matter, at this specific time. Both stages have to be met before a finding of incapacity is safe to make.

I give the person every practical chance to be involved before concluding otherwise. That might mean simplifying language, using pictures or written prompts, involving a trusted family member to help communication, or returning at a time of day when they’re more alert. Where I do conclude someone lacks capacity for a particular decision, I document exactly why, referencing what I observed against each of the four elements, so the assessment can be scrutinised by a solicitor, the Court of Protection, or the family themselves.

Because I am independent of the local authority, my findings are not shaped by a service’s resources or an organisation’s risk appetite. I report what the evidence shows, whichever direction that points.

“Ashley approached my relatives with real compassion, taking the time to listen to them properly, something other professionals hadn’t done. His assessment was thorough and clearly reasoned. I’d recommend him without hesitation.”
Rebecca

What Happens When Capacity Is Genuinely in Doubt

If, after all of that, someone does not have capacity for a specific decision, any choice made on their behalf has to follow the best interests principles in the Act: it must reflect their known wishes and values as closely as possible, and it must be the least restrictive option available. Losing capacity for one decision does not mean losing it for every decision, and it never removes someone’s right to be consulted and involved in what happens next.

This article sets out general principles under the Mental Capacity Act 2005 for England and Wales. Every capacity situation has its own facts, and this is not a substitute for a formal assessment of a specific person’s circumstances.

Every family I work with is dealing with a different mix of diagnosis, relationships and worry, and there’s rarely a neat answer that fits all of it. If you’re trying to work out whether a capacity assessment is needed, or you’re unsure whether a decision already made was handled properly, get in touch and we can talk through where you stand.

Straight Answers to the Questions Families Actually Ask