Assessing mental capacity is a recurrent component of psychiatric medicolegal work, and neurodevelopmental disorders like ASD, ADHD, and Intellectual Disability can impact capacity, and the assessment process itself. Let’s begin by revisiting the essential aspects of any mental capacity assessment. 

Firstly, the Mental Capacity Act 2005 insists that EVERYONE has capacity until proven otherwise. It is very clear that making an ‘unwise’ decision is not evidence of lack of capacity. 

Secondly, assessment is around a SPECIFIC decision, at a SPECIFIC time. For example, someone may have capacity for what clothes to wear but lack capacity around medication management. Specificity of time reflects that environments, some disorders, and someone’s understanding can change over time. A lack of capacity today does not mean a lack of capacity forever.  

Lastly, the functional test for capacity addresses the four following points: 

1. The person understands information relevant to the decision at hand.  
2. The person can retain that information long enough to decide.  
3. The person demonstrates the ability to use or weigh-up information as part of the decision-making process.  
4. The person can communicate their decisions.  

In medicolegal practice, it is also important to distinguish between diagnosis and the legal question of capacity. A diagnosis of ASD, ADHD, or Intellectual Disability does not determine whether someone has or lacks capacity. The assessment must consider whether there is an impairment of, or disturbance in, the functioning of the mind or brain, and whether that impairment means the person is unable to make the specific decision in question. This distinction is particularly important for solicitors, as capacity opinions should not rely on diagnosis alone, but should explain the functional impact of that diagnosis on the relevant decision. 

This distinction between diagnosis and the legal question of capacity arises across psychiatric practice, particularly where cognitive impairment may affect decision-making without automatically determining the legal outcome.

For instructing solicitors, clarity around the decision being assessed is crucial. Capacity to conduct litigation, capacity to approve settlement, capacity to manage finances, capacity to consent to treatment, and capacity to make decisions about care or accommodation are separate questions. A useful letter of instruction should therefore identify the precise decision, the relevant timing, the information the person needs to understand, and any known communication or sensory needs that may affect the assessment. 

Where capacity assessment is a central issue in litigation, the expert should be matched not only by psychiatric discipline but also by experience of the particular legal decision being considered.

Autism Spectrum Disorder (ASD) 

Individuals with ASD can present with strong verbal abilities and apparent understanding yet still struggle with decision making. Common issues during assessment revolve around interpretation and rigidity.  

Individuals with ASD can interpret language literally, struggle with ambiguity, and rigidly focus on certain aspects of communication. Answers to questions may appear inconsistent or unrelated if the person has misinterpreted what has been said. Whilst this may reflect a lack of capacity, it is our job to ensure we have done all we can to match the person’s ability to allow them to understand the relevant information.  

Rigid thinking could create difficulty with weighing-up information, leading to difficulties seeing a decision from alternative perspectives. Again, clear and direct communication can help with this, and it can be helpful to empathetically challenge positions held by the individual to demonstrate their ability to use information. It is possible that rigid cognition impacts someone’s capacity around a decision (i.e. a rigid autistic routine is unhealth/dangerous of the individual, but they are unable to even consider/imagine acting in a manner that does not include their rigid routine).  

Also, the term “masking” may be familiar to some, but what this essentially describes is a tendency for neurodiverse individuals to alter their behaviour to disguise confusion or misunderstanding, with the intention of not drawing attention to their difficulties. This can lead to confusion in a capacity assessment, and perceived agreement with the assessor must be explored if masking is thought to be occurring. 

Attention-Deficit Hyperactivity Disorder (ADHD) 

In general, the main difficulty in those with ADHD is less understanding of information per se, but more about sustaining attention and retaining information adequately to feel informed enough to decide. The question of understanding information then falls more onto whether the person has been able to focus adequately enough to appreciate the relevant information. Also, if inattention is an issue, then the retention of information will also be impacted. This is complicated by capacity assessments, which can cover complex scenarios, multiple components of a decision, and can potentially be lengthy.  

Additionally, impulsiveness can impact the criteria of weighing-up information, where a person with ADHD might lean towards a certain outcome in order to move the assessment along, as a reaction to growing frustration, or not allowing themselves the mental space to truly weigh up the choices. Also, the person may show the understanding of consequences at the time of assessment but act differently under moments of stress and pressure.  

Intellectual Disability 

Often, the difficulties that can arise with a person with intellectual disability relate to the understanding of abstract concepts involved in decision making, as well as retaining information. Assessors may sometimes take for granted what concepts are assumed as understood when any of us decide, and it is important to ensure all aspects are discussed and considered with the person before commenting on capacity.  

The assessor’s use of complex language, or speed of questioning, can impact a person’s understanding and weighing up of information, and the use of more direct and simplistic terminology can at times allow the person to demonstrate good understanding of the topic at hand.  

Repetition of what the assessor has said, and acquiescence can mimic understanding and retention of information, and it is important to evaluate if the person can communicate the information in their own manner.  

Practical Considerations for Assessment 

Here is a list of suggestions that tend to assist in all three scenarios, though for different reasons: 

• Use simple, concrete language.  
• Avoid abstract and hypothetical phrasing.  
• Break information into smaller pieces.  
• Allow time for processing. Offer breaks to tackle cognitive fatigue.  
• Use visual and written aid.  
• Consider the sensory aspect of your assessment (i.e. lighting, size, smells, furniture, etc.) 
• Use the person’s own language and phrasing.  

It is also crucial to let the person know that it is ok to say they don’t know an answer, and to reassure them that they will not be judged for any of their responses. Encourage questions and clarification and try to show that this interaction is a two-way co-operative effort, and not a ‘test’ for the person to pass or fail.  

From a solicitor’s perspective, a robust opinion should set out not only the conclusion, but also the steps taken to support the individual’s decision-making. This might include simplifying information, allowing additional processing time, using written or visual prompts, checking understanding in the person’s own words, and considering whether anxiety, fatigue, masking, sensory discomfort, or acquiescence affected the assessment. 

Where neurodevelopmental conditions are present, solicitors should be cautious about capacity conclusions that appear too brief or formulaic. A report that simply states that the person “understood the information” may not be sufficient if it does not explain how understanding was tested. Equally, a conclusion that a person lacks capacity should identify which part of the functional test was not met, why that difficulty arose, and whether further support or a different assessment environment might have changed the outcome. 

Conclusion 

Capacity assessments in neurodivergent individuals require more than a mechanical application of the Mental Capacity Act criteria. These disorders may affect communication, reasoning, attention, retention, and decision-making in different ways, sometimes subtly so. 

For instructing solicitors, it is important that assessments are undertaken by clinicians familiar with these neurodevelopmental conditions, and clinicians able to adapt their approach accordingly. A well-conducted assessment does not simply determine whether information has been presented, but whether the individual has genuinely been enabled to engage with it meaningfully.