Vulnerability or lack of capacity – how to spot the difference?

Have you ever wondered why some people with full decision-making ability still face serious risks — while others who lack capacity might not? That’s the crucial difference between vulnerability and mental capacity. 

Mental Capacity and Vulnerability are two concepts that often appear together.

Whilst they are two very distinct concepts, practice tells us that they are often confused and conflated – which can lead to poor outcomes for the individual’s concerned. 

What is Vulnerability? 

One of the problems is that there seems to be a multitude of different definitions for Vulnerability – depending on the sector you work in. 

The Solicitors Regulator Authority defines vulnerability as “Someone is vulnerable if they are at a higher risk of harm because they face barriers to participating effectively in court proceedings. People can be vulnerable because of: Permanent or long-term vulnerabilities including deafness, learning difficulties and age-related conditions”.

Whereas the Care Act 2014, defines a Vulnerable Adult as someone aged 18 or over who needs care and support, is experiencing or at risk of abuse or neglect, and is unable to protect themselves as a result of their care and support needs. 

We also have the FCA defining a vulnerable customer as someone who, “due to their personal circumstances, is especially susceptible to harm, particularly when a firm is not acting with appropriate levels of care”. This susceptibility can stem from various factors, including poor health, significant life events, low financial resilience, or limited ability to understand financial matters. 

However, whilst they all seem to have a different viewpoint and emphasis, there is one underlying feature – that of risk of harm. 

What is Mental Capacity? 

This is different to Mental Capacity which relates to a person’s ability to make a specific decision. It is clearly defined in the Mental Capacity Act (2005) and associated guidance, which inform us it is related to a person’s ability to understand, retain, weigh up and use and communicate relevant information. 

In short then:

Vulnerability = Risk of Harm 

Mental Capacity = A person’s ability to make a decision 

And it is possible to lack capacity and not be vulnerable and vice versa for example Jane, aged 82, lives alone and struggles to afford heating — she has full mental capacity but is vulnerable due to financial hardship. Meanwhile, Peter, aged 45, has a brain injury and cannot understand or weigh up tenancy agreements however, he has a deputy that takes care of that for him — he lacks capacity but isn’t currently at risk because his housing is secure. 

Practical Advice: What to Do in Practice 

My advice would always be to start by determining if a person has capacity in relation to the specific decision or situation at hand. If they don’t then the Mental Capacity Act and associated guidance provide us with a clear pathway as to how to proceed. 

If they have capacity but are also vulnerable then it is about determining what they are at risk from, the level of risk they are exposed to and working with the individual to best help them manage this. 

Why the Distinction Matters 

Distinguishing between vulnerability and lack of capacity isn’t just an academic exercise — it has real-world consequences for the people we support.

Confusing one for the other, can lead to unnecessary restrictions, missed safeguarding opportunities, or failing to uphold someone’s autonomy.  

Mental capacity is a legal construct centred on decision-making ability, while vulnerability is about exposure to risk — with or without impaired capacity. Recognising the difference helps practitioners provide proportionate, ethical, and lawful support.  

When in doubt, lead with a capacity assessment, and if capacity is present, explore the extent of the risk and it’s cause, and manage appropriately.