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Home » Case study: The diagnostic step and the causative nexus

Case study: The diagnostic step and the causative nexus

Manor house on a misty day

The diagnostic step is a simple but often misunderstood part of the Mental Capacity Assessment. One of the most common errors is to simply list a medical diagnosis without any explanation of how the diagnosis impacts upon decision-making. However, this link – also known as the causative nexus – is the vital point on which the rest of the assessment is based. It is therefore important to understand exactly why the diagnostic step is important and how to document it properly.

Two familiar characters

To support our case study, I would like to introduce two characters, who may be familiar to some readers. These are: Mr Toad and Dory.

Character #1: Mr Toad

  • Mr Toad lives alone in a large manor house.
  • He is well known for his energetic and short-lived hobbies,
  • He has a diagnosis of Attention Deficit Hyperactive Disorder (ADHD) and depression. He presents with a short attention span, reduced focus, reduced sleep patterns, impulsive decision making, hyperactive mannerism and fast-paced speech.
  • When taking medication and accepting support, Mr Toad can engage well and manage his activities of daily living with prompts and verbal support to help rationalise decisions.
  • However, Mr Toad also experiences periods of low mood. This can result in a lapse in his daily medications. This can then cause a deterioration in presentation, leading Mr Toad to become increasingly impulsive and make decisions that are considered highly ‘risky’.
  • Following a series of ‘near misses’ in the pursuit of his high-risk hobbies, questions have been raised around Mr Toad’s ability to manage his property and affairs. There is a reasonable belief that Mr Toad may lack understanding around the risks and benefits of his decisions when not taking his medication. As such, a Mental Capacity Assessment has been requested in order to ascertain if he has the capacity to make decisions around his property and financial affairs.

Character #2: Dory

  • Dory is 20 years old. She has a large family and many friends. She is very sociable and likes to go out as much as possible. She also loves to swim and has taken part in many competitions.
  • Unfortunately, Dory suffered a Traumatic Brain Injury (TBI) while training for a national competition. This has had a long-lasting impact on her short-term memory.
  • Dory and her family have recently moved home. This has impacted Dory greatly as she had previously been familiar with her route to the shops and local café, but now frequently gets lost if she is not accompanied by another person. She also often forgets her phone. 
  • Given Dory’s issues with forgetfulness, Dory’s family have been in contact with their social worker, considering the different types of tracking technology so that if she does not return by a certain time, they can call her or know where she is. However, they are unsure if Dory fully understands the tracking technology and how it would monitor her. Therefore, they have requested a mental capacity assessment in order to check whether Dory can make a decision about making use of a ‘lifeline’ to track her and keep her safe.

Mental Capacity and the diagnostic step

There are a range of short and long term conditions that can impact Mental Capacity. In order to frame the diagnostic step, we should consider two key questions:

  • Does the person have an impairment of, or disturbance in, the functioning of the mind or brain (whether permanent or temporary)? 
  • Does the impairment or disturbance mean that the person is unable to make a specific decision when they need to?

It is this second part which is absolutely crucial, as conditions can have a whole range of presentations and intensities of impact. If an assessor were to use the diagnosis alone to justify a ‘lack of capacity’ in any given area, then this would contravene the whole purpose of the Act, which is designed to support capacity and protect people’s Rights.

Therefore, it is absolutely vital that in any Mental Capacity Assessment, a justification must be included to determine if/how the diagnosis impacts upon the individual’s ability to make a specific decision.  

The case of Mr Toad

Based on the context above, the diagnosis step of an assessment for Mr Toad might read as follows:

Mr Toad has a diagnosis of ADHD, that was diagnosed at the age of 14, and depression which was diagnosed at 29. These conditions present with periods of greatly fixated behaviour on a specific ‘thing’, then in contrast having a short attention span in other areas, struggling to hold focus and engage. Further, Toady presents with difficulties processing information outside of these areas of intense focus. Nor does he demonstrate retention of information for related risks. These diagnoses therefore directly affects his cognition and ability to make decisions.

The case of Dory

In a similar way, the case of Dory might include a diagnosis step such as this:

Dory experienced a TBI at 17 years old, which has impacted her short-term memory. This presents with difficulties retaining new information, repetition of speech, word finding difficulties and a short attention span. Recognising this, it is my professional opinion that Dory’s diagnosis directly impact her decision making and cognition for this decision. 

Remembering the causative nexus

The key here is to link the diagnosis – either the ADHD and depression of Mr Toad, or the TBI of Dory – so a specific issue with making decisions. Without this crucial element, the Mental Capacity Assessment may not be valid.

Once this section is complete, then the rest of the Assessment can be continued as usual. 

For further information on this topic, as well as help and support in conducting Mental Capacity Tests to a gold standard, please get in touch.

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