Building on our previous work,11,14
the results from this pilot RCT suggest that, relative to SMC alone, CBT (plus SMC) produced a greater reduction in PNES frequency at the end of treatment ( and ). There was a tendency for this benefit to be maintained at the 6-month follow-up, when there was also a trend for CBT to be more likely to have resulted in 3 consecutive months without PNES. We also observed some reduction in PNES frequency in our SMC group, suggesting that our standard outpatient neuropsychiatric care offered patients some benefit. There was an overall improvement in self-rated social functioning; CBT was not differentially more effective over time in this respect. While we observed no changes in mood and observed only minimal improvements in health service use, the current study lends weight to the potential contribution of CBT to the management of PNES when compared directly to another treatment.
Our CBT approach is predicated on the assumption that PNES represent dissociative responses to arousal,27
occurring when the person is faced with fearful or intolerable circumstances.11,16
Our treatment model emphasizes seizure reduction techniques especially in the early treatment sessions and most of the CBT group will have been exposed to these techniques. While the usefulness of seizure remission as an outcome measure has been questioned,28
seizures are the reason for patients' referral for treatment. Despite being seizure-free, some patients may remain unemployed or dependent on benefits.28,29
The absence of change in HADS scores was unexpected11
but may reflect low pretreatment scores, providing less scope for change. This finding may also reflect the heterogeneous nature of the patients, who presented with a range of comorbid diagnoses, including somatoform (nonseizure) disorder, eating disorder, and personality disorder, and relate to reports of PNES occurrence in the absence of raised levels of general anxiety.27
Our pilot RCT has a number of limitations. Our SMC condition did not control for therapist contact, which was greater in the CBT group. Another limitation concerns the difficulty of rendering psychological treatment studies such as this blind: whether the patients were receiving CBT could not be concealed from the neuropsychiatrists providing SMC. We cannot determine how this influenced the number or content of the SMC sessions.
Other important limitations concern sample size and selection. Our study was designed to detect a large treatment effect yet we found only a medium effect size at follow-up. Furthermore, in planning the study, our assumption of no improvement in the SMC group was not borne out in our outcome measures. Our clinical service is specialized. Patients referred to us have typically not responded to routine interventions in neurology clinics, which may themselves constitute a highly effective treatment.30
Thus, a selection bias in favor of chronic, more difficult-to-treat patients might exist. However, patients had at least accepted referral to a psychiatric service, which some of the most intractable patients may refuse to do. Willingness to enroll in the study might also indicate motivation to reduce seizure occurrence and explain the SMC group's improvement. Additionally, our SMC is an intervention, so we cannot comment on a potential comparison between the benefits of CBT vs no treatment at all. Although our results are not readily generalizable to nonspecialist settings,31
they are likely to be generalizable to other specialist services with an interest in both neurologic and psychiatric management of PNES. We chose to exclude patients with comorbid epilepsy to facilitate measuring outcome in terms of PNES frequency. It has been suggested that such patients might benefit from psychological interventions13
and our study provides no contradictory evidence. While ideally all patients would have been diagnosed on the basis of video-EEG telemetry, with a low seizure frequency this is not always feasible and our groups were well-matched for diagnostic methods.
Although primary outcomes were analyzed for almost all participants, statistical power may have been reduced: some patients were unwilling to complete the secondary outcome questionnaires (which were also not completed by patients prior to treatment arm assignment) () and seizure freedom could not be evaluated in 7/66 patients. Finally, our 6-month follow-up may have been too short to observe a change in employment status; indeed, the older age of some participants and financial incentives derived from state benefits may have dissuaded people from seeking work.
Larger multicenter studies would allow comparisons between CBT and other psychological interventions controlling for therapist contact. They would also permit investigations of predictors of treatment response.32
This will help identify patients most likely to benefit from treatment and improve clinical decision-making. Additionally, such studies would permit greater examination of the magnitude of therapist effects.33
Longer posttreatment follow-up would provide a better comparison of treatment outcomes to the natural history of PNES.29
These limitations notwithstanding, our results suggest CBT can reduce PNES occurrence. Further investigation of those who may benefit most from CBT may offer increased opportunities to treat this disabling disorder.