ADHD, autism and brain injury claims: establishing what changed

I am asked to assess a growing number of claimants who have sustained a brain injury and who also have ADHD or autism. Sometimes the neurodevelopmental diagnosis was made years before the accident. Increasingly, it is made afterwards, occasionally during the litigation itself. Either way, the instructing solicitor usually wants an answer to the same question: what has the injury caused? 

If the claimant was diagnosed with ADHD or autism before the accident, the issue is usually one of distinguishing baseline impairment from additional injury-related disability. If the diagnosis was made afterwards, the analysis can be more complicated. The answer is not straightforward, because the two sets of problems overlap significantly. 

For solicitors, that distinction can be central not only to causation but also to the assessment of the claimant’s ongoing needs and losses. Establishing a reliable pre-accident baseline allows the expert to consider which difficulties were already present, which have genuinely changed following the injury, and whether previously manageable traits have become functionally disabling. 

Late diagnosis 

ADHD and autism are neurodevelopmental conditions. They were present in childhood, whether anyone recognised them at the time. Adult diagnosis has become far more common over the past decade, and plenty of people reach their forties before anyone puts a name to lifelong difficulties, particularly if they were academically able, well supported at home, or settled in work that happened to suit them. 

A diagnosis of ADHD or autism made after an accident therefore usually identifies something old rather than something new. That cuts both ways in litigation. A claimant cannot sensibly attribute lifelong difficulties to a recent injury. Equally, a defendant cannot dismiss genuine post-injury deterioration simply because a longstanding condition has now acquired a name.  

The timing of a diagnosis should therefore be considered carefully. A post-accident diagnosis does not necessarily mean that the condition itself was caused by the accident, but neither does it answer the separate question of whether the injury has worsened the claimant’s ability to manage its effects. Solicitors may need to distinguish clearly between the presence of a pre-existing condition and a post-injury change in the claimant’s level of function. 

This makes pre-accident evidence particularly valuable. School reports, university records, occupational history, GP and mental health records, and evidence from parents, partners or long-standing friends are often crucial to my assessment. 

Contemporaneous evidence can be particularly important where retrospective accounts differ. Records showing educational attainment, employment stability, absence levels, performance concerns, previous treatment and the support provided by family members can help test the claimant’s reported pre-accident function against the wider factual evidence. Witness statements may also reveal informal support that would otherwise be invisible in the medical records. 

Function matters more than the label 

When I assess these cases, the diagnostic status interests me less than what the claimant could do before the accident. I have seen claimants with pronounced ADHD traits who nevertheless held down demanding jobs and ran busy households, because they had built strong coping mechanisms to manage their difficulties. 

The expert therefore needs to reconstruct not simply what symptoms or disorders existed before, but how the claimant managed them. Were they chronically late? Did a partner organise appointments and bills? Did they repeatedly change jobs? Did they avoid socially demanding environments? Was their apparent independence dependent on rigid routines or unusually high effort? 

The assessment must reconstruct such coping systems. In many cases of ADHD or autism, years of stable functioning depend on predictability and control of the environment. The brain injury can easily dismantle the scaffolding that made everyday life manageable, resulting in significant functional deterioration. 

This functional comparison can have consequences beyond diagnosis. A claimant who appeared independent before the accident may, on closer examination, have relied on carefully developed routines or low-level family support. Equally, a post-injury increase in supervision, prompting or practical assistance may represent a genuine additional need. Understanding what support existed before and what is required now can therefore be important when considering care, rehabilitation and future loss. 

Causation is rarely either/or 

Solicitors sometimes ask me to say whether a given difficulty is “the ADHD” or “the brain injury”. Often the honest answer is both. A claimant with pre-existing ADHD may always have been distractible. If the injury then slows their processing and worsens their fatigue, previously manageable difficulties can become disabling. That deterioration is attributable, at least in part, to the injury. A pre-existing condition may also explain why an apparently modest injury has had a disproportionate effect. 

Conversely, new concentration problems after an accident do not automatically reflect damage to the brain or exacerbation of ADHD. Pain, disturbed sleep, low mood, anxiety, medication and post-traumatic symptoms all impair cognition, and in my experience, they account for a good deal of what claimants' report, particularly after milder brain injuries. Weighing these possibilities against the severity of the injury, the pre-existing conditions, and the chronology of the complaints is often at the core of my work. 

This is why instructions framed simply around whether a symptom is attributable to ADHD, autism or brain injury may be too narrow. The more useful medico-legal question is often how the claimant’s overall functional position has changed since the accident, which factors probably account for that change, and what difficulties would likely have existed in any event. A clear chronology of symptoms, treatment and functional deterioration can be particularly helpful in addressing those questions. 

Prognosis: can the coping system be rebuilt? 

Prognosis in these cases turns less on neurological recovery than on adaptation. Someone who spent years developing routines around their ADHD may be unable to rebuild them with less stamina and slower thinking. When I address prognosis, I ask whether the old strategies can realistically be restored, whether ADHD medication has been reviewed and optimised since the injury, whether the employer can adjust the role, and whether rehabilitation has been tailored to how this particular person functions. Standard rehabilitation programmes tend to assume a neurotypical viewpoint, and they can therefore fail neurodiverse patients. 

For solicitors considering prognosis and quantum, it may therefore be important to distinguish between treatment aimed at neurological recovery and support aimed at enabling the claimant to function with the combined effects of their injury and neurodiversity. Recommendations for rehabilitation, workplace adjustments or support should reflect the individual claimant rather than assuming that a standard pathway will necessarily be effective. 

What solicitors can do early 

The quality of my opinion depends heavily on the material I am given. I would highlight: 

• education and employment records from before the accident, including school reports; 
• GP and mental health records covering the whole of the claimant's life; 
• the referral letter and assessment report for any ADHD or autism diagnosis, together with the date and the reason the referral was made; 
• detailed statements from people who knew the claimant well before and after the injury; 
• details of pre-accident support, formal or informal, including what family members quietly did without ever calling it “care”; 
• treatment, rehabilitation and medication changes since the injury. 

Obtaining this evidence early can also reduce the risk of the expert being asked to form an opinion from an incomplete baseline. Where possible, witness evidence should address specific examples of function before and after the accident - such as work, finances, household tasks, appointments, relationships, social activity and the ability to cope with changes in routine - rather than relying solely on general descriptions that the claimant was “better” or “more independent” before the injury. 

The questions worth asking 

I would encourage solicitors to frame their instructions functionally: what could this person do before the accident, what can they do now, why did that change, and how much of the change is likely to persist? A report built around those questions serves the court far better than one that focuses on arguments about diagnostic labels. 

Those questions also provide a useful framework when considering the wider claim: what was the claimant’s likely trajectory but for the accident, what additional restrictions or needs have arisen because of the injury, and which of those are likely to remain in the longer term? Keeping the focus on demonstrable change in function can help ensure that the expert evidence addresses the issues most relevant to causation, prognosis and quantum.