Summary of main findings
This is the first randomised controlled trial to examine the use of gut-directed hypnotherapy in patients not referred to tertiary care. It is also the first to report long-term outcomes (to 12 months). Both the hypnotherapy and control groups demonstrated some improvement over time. This result is in line with expectations for a trial involving a chronic relapsing condition with patients being recruited at the time of a primary care consultation, which would suggest a relapse in their condition.
Patients randomised to gut-directed hypnotherapy showed significant improvement in symptom scores (pain and diarrhoea) at 3 months compared with control patients, but this between group difference was not sustained over a longer period of time. Other measures used failed to demonstrate any significant between-group differences.
Strengths and limitations of the study
This article does not report a definitive trial of hypnotherapy for IBS and its most notable limitation is that the lack of a third arm (controlling for additional time and attention) means that conclusions can only be drawn about the potential and efficacy of the multicomponent intervention in its entirety. This may or may not be a significant limitation depending on the perspective from which findings are viewed, although identification of active components of a multicomponent therapy is important to minimise both cost and risk of harm.
Incomplete follow-up may have biased symptom and quality-of-life results, however Little's D test indicated that the missing data were missing completely at random (MCAR) (D = 1017, degrees of freedom = 1161, P = 0.99) and statistical analyses using multiple imputation gave similar results to those presented. Our equivocal findings with respect to the benefit of hypnotherapy may be for several reasons. It is possible that hypnotherapy has no significant benefit over conventional treatment alone in terms of symptom and quality-of-life improvement. A second interpretation of the data would be that a benefit does exist, but the study was underpowered to identify this. The study was powered to detect a medium-sized change (SD = 0.6) and aimed to recruit 100 people. In total, 81 were randomised and 53 provided outcomes data at the 12-month follow-up. These 53 patients would enable a medium-sized change to be detected with only 58% power at the 5% significance level. Therefore, it remains a possibility that a type II error has occurred or that a much smaller change in scores is conferred by hypnotherapy; this explanation is indicated by our data in Figure 2.
There also exists the possibility of a type I error due to multiple statistical testing, and noted differences may be spurious, although previous evidence and the consistent trend towards benefit in the intervention arm suggest that differences, where identified, are real. The significant difference in the use of prescription medication suggests that, although conventional measures of symptom and quality of life are not significantly affected by the delivery of hypnotherapy, patients may be able to maintain these scores with reduced recourse to medication. This should be explored further using prescription data. The third interpretation of these data is that a significant benefit is conferred by hypnotherapy but that the outcome measures used were either not sensitive enough to detect this or were inappropriate.
The hypnotherapy group reported a range of benefits suggesting that treatment had improved their ability to manage their symptoms, their confidence, and overall wellbeing. These factors were not routinely measured in this trial and similar data is not available from control patients, meaning attribution bias cannot be excluded. The inclusion of a third control arm and incorporation of more generic outcomes would be advised in future work to allow this to be investigated.
Other explanations relating to the treatment programme may explain our findings. It is possible that gut-directed hypnotherapy does confer long-term benefit for this patient group but the delivery of therapy in this trial was suboptimal and, therefore, benefit not demonstrated. As such, it remains a possibility that delivery of the therapy in another way — for example more sessions, longer sessions, different induction strategies, or a different therapist — may have demonstrated benefit. However, at the outset of this study we aimed to use a therapy programme that, if proving effective, could be accessed and provided by primary care practitioners. It could be argued that longer, intensive programmes would not achieve this aim. In spite of this, future work should aim to evaluate different treatment modes and should evaluate the effect that patient compliance (for example, use of provided audiotapes) has on outcome.
Comparison with existing literature
The finding of a significant difference in overall symptom scores and diarrhoea symptoms between groups mirrors results found in Whorwell et al's original trial,23 where a significantly greater reduction in pain was observed in intervention patients at 12 weeks. That trial did not provide follow-up on both groups beyond 3 months, although long-term follow-up of patients with severe refractory IBS receiving hypnotherapy has been reported elsewhere19 and suggests long-term benefit. Control population data over an extended time period is needed to confirm this, although it is possible that longer-term benefit not demonstrated in this study may be observed in those patients with severe disease as they have greater potential for improvement than patients recruited from primary care.
Implications for future research and clinical practice
Having taken all of these findings into account and put them into context, we report that gut-directed hypnotherapy does benefit patients with IBS in terms of reducing symptoms and medication use. However, the lack of any significant difference between the groups in symptom and quality-of-life scores beyond 3 months would prohibit the more widespread introduction of this therapy without further evidence. The findings of this study support the urgent need for a large well-designed trial incorporating a robust economic analysis.