Functional neurological disorder (conversion disorder) is a common cause of disabling neurological symptoms. Despite its frequency in normal medical practice, it has occupied an unenviable twilight zone in terms of understanding its pathophysiology.

The most pervasive idea has been that traumatic life events, in particular childhood trauma, are causal. There is a logical consequence of this idea, encapsulated in the theory of conversion disorder put forward by Breuer and Freud, that treatment of this disorder rests on the uncovering, exploration and resolution of the underlying trauma, through which symptoms will disappear (Freud and Breuer, 1978).

Over the past 15 years there has been increasing interest in functional neurological disorder (FND), and with it a questioning of the relevance of traumatic life events. Within DSM 5, changes to diagnostic criteria demoted the presence of a psychological formulation as a supporting but not essential criterion, and instead emphasis was placed on the demonstration of specific features on history and examination that were positive features of functional neurological disorder.

Against this background, Ludwig et al performed a meta-analysis of studies that had looked at the association between adverse life events and functional neurological disorder.

Methods

The authors searched for case control studies that recorded life events in patients with functional neurological disorder/conversion disorder that were indexed in PubMed and ScienceDirect between 1965 and 2016. They also searched reference lists for eligible studies and reviews.

They included studies with more than 10 subjects where they included comparison between functional neurological disorder patients and at least one control population. They performed standard ratings of study quality and calculated odds ratios and population attribution factors (PAF), which is a measure of the contribution of a risk factor to a disease at a population rather than individual level.

Results

The authors identified 34 eligible studies with a total of 1,405 patients.

Rates of childhood stressors

	Functional neurological disorder	Controls	Odds ratio (95% confidence interval)
Emotional neglect	49%	20%	5·6 (2·4 to 13.1)
Sexual abuse	24%	10%	3·3 (2·2 to 4.8)
Physical abuse	30%	12%	3·9 (2·2 to 7.2)

Stressful life events preceding onset were also more common in patients with FND when compared with controls.

However, a notable proportion of patients did not appear to have either childhood maltreatment or recent stressful life events.

The quality of studies was low-moderate.

Conclusions

The analysis suggests that adverse experiences both in childhood and adulthood are associated with the development of functional neurological disorder. However, there was considerable heterogeneity both in the nature of the adverse experiences and also if they occurred at all, with a notable proportion of people reporting no such events.

Strengths and limitations

The main limitations relate to the quality of the studies sampled for the meta-analysis. Multiple methods were used to assess life events and childhood trauma, and of course all such assessments were retrospective. In studies with arguably more rigorous methods of life events ascertainment, a higher rate of adverse life events prior to onset of symptoms was found.

Implications for practice

The idea that adverse childhood and later experiences have an influence on risk of developing (mental) illness is not a new one. For example, rates of adverse events in people with schizophrenia and depression are high. However, in functional neurological disorder these events have seemed to morph from risk factors/associations to the cause. This has had a number of negative consequences:

1. Firstly, it suggests that diagnosis requires the presence of these factors. Under previous iterations of DSM it was not possible to make the diagnosis of conversion disorder without there being a “psychological formulation”. This illogical situation led to some patients being passed between neurologists and psychiatrists in an anti-therapeutic game of ping pong, with neurologists declaring the symptoms to be “non-organic” and psychiatrists declaring the patient to be “psychologically well”.
2. Second, it suggests that the only treatment that will help is one that is directed towards the uncovering and resolution of underlying traumatic experiences. In contrast, treatments that work at the level of how symptoms are produced, delivered by psychologists, physiotherapists, occupational therapists were not prioritised or viewed as legitimate or valuable.
3. Third, it subsumes the reality of the physical symptoms experienced by the patient within another phenomenon (past trauma) as if the symptoms are not a thing in their own right, and, in a sense, are not real.

Importantly, this paper is not an excuse to throw out the idea of an association between adverse life events and functional neurological disorder; rather it calls for us to consider the mechanism of the association and to understand how this should influence treatment (and even prevention). It supports the rebalancing of diagnostic approach, explanation and treatment that has been promoted in recent times and (at the very least) supports allowing the disorder to be classified in ICD-11 in the neurology and psychiatry sections. However, as the authors point out, the hope would be that in the end there would be a merging of these categories to one that recognises the indivisible nature of brain and mind.

Conflicts of interest

I was a reviewer for the paper and have previously published papers with several of the authors.

Links

Primary paper

Ludwig L, Pasman JA, Nicholson T, Aybek S, David AS, Tuck S, Kanaan RA, Roelofs K, Carson A, Stone J. (2018) Stressful life events and maltreatment in conversion (functional neurological) disorder: systematic review and meta-analysis of case-control studies. The Lancet Psychiatry 2018

Commentary. The Lancet Psychiatry 2018

Other references

Freud S, Breuer J. (1978) Studies in hysteria. Harmonsworth, UK: Penguin; 1978.