Addressing psychiatric injury causation in personal injury litigation

In personal injury litigation, establishing a causal link between an index event and a psychiatric condition requires a methodical analysis of a claimant’s pre-existing health, the nature of the stressor, and the temporal proximity of symptoms. Expert opinion must assess whether a condition would have developed regardless of the index event, or whether the event acted as the proximate cause for the current impairment. While clinical assessment remains the foundation, the medicolegal report must address the distinction between a clinically recognised disorder and transient distress.

The scope of psychiatric evidence

An expert report must distinguish between normative distress following an accident and a recognised psychiatric condition. Where a diagnosis is reached, the report should address the clinical evidence supporting that diagnosis, the impact on functioning, and the prognosis. This process requires a review of relevant longitudinal data, such as GP records or occupational documentation. Solicitors may review standardized reports detailing common psychiatric conditions alongside the claimant’s specific history to help identify whether an injury represents a new onset or the exacerbation of a latent condition.

Evidential base and information gaps

The reliability of a causation opinion depends on the consistency of the evidence. Gaps in clinical records, such as an absence of prior mental health consultations, do not inherently preclude the presence of a prior condition. If an expert proceeds without complete records, they should state this limitation explicitly, as it may influence the court’s assessment of whether a condition was asymptomatic but present. Under the overriding duty of the expert to the court per CPR Part 35.3, the opinion must be supported by the available factual evidence; where records are incomplete, the expert should clarify whether this prevents a definitive view on causation.

Causation and competing stressors

The standard of causation generally requires the claimant to establish that the injury would not have occurred ‘but for’ the defendant’s negligence. Where multiple stressors are present, the expert should endeavour to disentangle the effects of the index event from other life events. A ‘material contribution’ argument is considered in limited circumstances where the expert identifies that the breach made a significant contribution to the injury, even if not the sole cause. An expert should provide a clear medical rationale linking the specific trauma to the condition, while considering alternative explanations.

Interdisciplinary considerations

Psychiatric injury often intersects with chronic pain or physical trauma. An expert psychiatrist may address the psychological consequences of pain but should avoid opining on the source or validity of physical symptoms, which fall under the purview of orthopaedic or pain management specialists. If experts in different disciplines reach conflicting views, the court may direct them to engage in discussions under CPR 35.12 to identify areas of agreement and disagreement. A joint statement produced in this manner serves to narrow the issues for trial.

Assessment of capacity

In cases involving cognitive impairment, the expert’s role may extend to an assessment under the Mental Capacity Act 2005. If the instructions include an assessment of decision-making capacity, this must be stated clearly, as the legal tests for capacity are distinct from psychiatric diagnosis. The expert’s duty remains focused on providing an independent, evidence-based opinion that assists the court in resolving the issues in the litigation.

• Ensure the letter of instruction specifies if a capacity assessment is required.
• Review whether the expert should be instructed under CPR 35.8 as a single joint expert or as a party-appointed expert.
• Monitor for instances where the court may request a joint statement under CPR 35.12 to clarify conflicting medical views.