Insight vs Understanding: Clarifying the Distinction in Mental Capacity Assessments

The concept of insight is frequently used in clinical settings, yet its meaning—and its role in mental capacity assessments—is often a source of confusion and debate.

Recent legal judgments have prompted renewed attention to how we use the term, especially in the context of assessing decision-making capacity under the Mental Capacity Act 2005. 

The Legal Context 

In Re Thirumalesh (Dec’d) [2024] EWCA Civ 896, the Court of Appeal clarified that a person’s apparent disbelief or rejection of the information they are given, does not automatically mean they lack capacity to make a decision. Capacity must be assessed based on the threshold of understanding, not on whether the person agrees with or accepts a diagnosis or prognosis. 

Building on this, in CT v London Borough of Lambeth & Anor [2025] EWCOP 6 (T3), Theis J further added to the debate on the use of the term insight in capacity assessments. In this judgement it was emphasised that: 

"Insight is a clinical concept, whereas decision-making capacity is a legal concept. Capacity assessors must be aware of the conceptual distinction and that, depending on the evidence, a person may be able to make a particular decision even if they are described as lacking insight into their general condition... If a lack of insight is considered to be relevant to the assessment of capacity, the assessor must clearly record what they mean by a lack of insight in this context and how they believe it affects, or does not affect, the person’s ability to make the decision as defined by the statutory criteria—for example, to use or weigh relevant information." 

In other words, the term insight may have clinical utility, but it cannot be used as a substitute for the legal test of capacity. 

What Do We Mean by "Insight"? 

One of the challenges is that insight is used differently across professional disciplines. While it is a familiar concept in mental health, its meaning varies depending on context and profession: 

• A psychiatrist or mental health nurse may use lack of insight to describe someone who does not accept that their hallucinations are part of a mental illness. 

• A social worker might say someone lacks insight when the person is unaware of the risks associated with their behaviour or environment. 

• A neuropsychologist may define it as “the ability to understand and apply information to inform a rational outcome.” 

  
  

These differing perspectives illustrate why relying on insight as a blanket term can be problematic in a legal context. Unless clearly defined, it risks creating confusion. 

Insight vs Understanding: What’s the Difference? 

So how do insight and understanding differ? 

A review of the literature and practice suggests that the key distinction lies in the depth and application of knowledge: 

• Understanding is typically about factual knowledge—the “what”. For example, “I have diabetes and I need to manage it with medication and diet.” 

  
  

• Insight, by contrast, incorporates an evaluative and reflective element—the “why”. It might involve understanding how diabetes affects the body, why management is necessary, and the consequences of non-compliance. 

Insight and Mental Capacity 

A good illustration of this in practice is the ruling of LBX v K & Ors [2013] EWHC 3230 (Fam). In this ruling the following information as relevant to the decision of care 

• What areas P needs support with  

• What sort of support they need  

• Who will provide such support  

  
  

It then also identified what is not relevant to an assessment of capacity as to care:  

• How care is funded  

• How overarching arrangements for monitoring and appointing care staff work;  

  
  

There is clearly a difference in the depth of what the courts expect us to understand.  

I can’t help thinking this brings us back to ‘What would we expect the average person on the Clapham omnibus to understand?’ 

Insight and Mental Capacity 

It’s important to emphasise that insight is not excluded from capacity assessments. The decision in CT v Lambeth does not prohibit the use of the term.

Rather, it urges clarity. If you reference lack of insight in your assessment, you must explain exactly what you mean by it, and how it relates to the person’s ability to meet the criteria set out in the Mental Capacity Act—particularly their ability to use or weigh relevant information. 

Final Thoughts 

Insight and understanding are not interchangeable terms. They represent different levels of awareness and application, and their roles must be carefully delineated in any assessment of capacity. As professionals, we must avoid relying on vague or discipline-specific language when legal standards require precision. 

Rather than abandoning the term insight, we should aim to define it clearly, contextualise it clinically, and translate its relevance into legal terms—namely, how it affects a person’s ability to understand, retain, use or weigh information, or communicate a decision.