In psychotherapy outcome research, many empirical studies have shown that cognitive behavioural treatments are efficacious for many disorders . In a recent systematic review of 27 studies, Hofmann and Smits  show that cognitive behavioural therapy (CBT) has proven to be an unquestionably efficacious treatment for adult anxiety disorder when compared to both pharmacological and psychological placebos. However, they conclude that there was considerable room for improvement. Moreover, the high complexity and co-morbidity that is often found with anxiety disorders sometimes requires the use of two or more treatment methods that are flexible and adjustable to one other . According to Kirsch, Lynn, and Rue  and Schoenberger , hypnosis can be integrated easily into current cognitive and behavioural interventions in clinical practice. Indeed, CBT and hypnosis share a number of aspects that render their combination natural; for example, imagery and relaxation, which are found in both techniques . Hypnosis has been used effectively in a variety of medical settings (surgery, dentistry, chronic pain management, labour etc.) and several studies report its efficacy in the treatment of anxiety disorders [7-13]. A recent systematic review of randomized controlled trials concludes that current evidence is not sufficient to support the use of hypnosis as a sole treatment for anxiety . However, in a meta-analysis, Kirsch, Montgomery, and Sapirstein  found that the addition of hypnosis to CBT substantially enhanced the treatment outcome for several problems (anxiety, obesity, pain, etc.). The addition of hypnosis to CBT helps the patient in several aspects of therapy, such as the preparation for in-vivo exposure, imagery exposure, developing coping skills, and cognitive restructuring [6, 16-18]. Moreover, patients using hypnosis effectively develop a better sense of self-efficacy, which is known to enhance self-regulation and is linked to lower psychological distress and better quality of life. Hence, hypnosis is worth exploring as an additional tool to improve traditional CBT.
In this chapter, we offer a comprehensive review of the literature regarding the use of hypnosis in the treatment of anxiety disorders. We will present evidence that supports its use or not as an adjunct treatment to CBT, also known as cognitive-behavioral hypnotherapy (CBH). We will also present evidence that does not justify its use as an independent treatment for anxiety disorders. Due to the amount of research on Post-Traumatic Stress Disorder (PTSD) and hypnosis, the reader will notice that a lot of the information will be related to PTSD. We will conclude by giving a simple guideline for practitioners interested in developing and using hypnosis as an adjunctive therapeutic tool in their practice.
2. Description and definition
Although under different names and applications, hypnosis has been depicted, described and documented in ancient civilizations (e.g. Egyptians, Greeks, Chinese, Indians, Sumerians, Persians and others) and was mostly used by healers. In his book
Burrows, Stanley, and Bloom  describe hypnosis as a technique that induces, through relaxed and focused attention, an elevated state of suggestibility. During this state, reduction in critical thinking, reality testing and tolerance of reality distortion allow the person to experience different phenomena (vivid imagery, drug free anaesthesia, drug free analgesia, and so on) that might otherwise be hard to attain . Contrary to common perceptions, hypnosis is a natural phenomenon which people experience in a lighter way several times a day . Daydreaming, being so absorbed by a book or movie that you do not hear someone calling your name or absent-mindedly driving past an expressway exit are all examples of shallow hypnotic states . According to the division 30 of the American Psychological Association (APA), a procedure becomes a hypnotic one when the following two components are present: an introduction in which a person is told that suggestions for imaginative experiences will come, and the first suggestion, which functions as the induction . Examples of suggestions during the introduction include: "I am going to ask you to imagine some changes in the way you think and feel. Is that ok? Let's see what happens" . The formulation of hypnotic suggestions is different from other types of suggestions (e.g. placebo, social influence), given the fact that it requests the patient to participate .The first suggestion might come directly after the introduction and is usually a suggestion to close the eyes, move the arm or hand or alter perception . Given that there are many types of hypnotic suggestions, standardized scales of suggestibility can be applied before someone undergoes formal hypnotherapy to see how suggestible the person is to all kinds of hypnotic suggestions . During ideomotor suggestions, a certain action, such as arm levitation occurs automatically without awareness of volitional effort by the person . Challenge suggestions occur when the hypnotised person is unable to execute an act that is ordinarily under voluntary control such as bending an arm . Cognitive suggestions also can be used to create various cognitive or visual distortions such as pain reduction, selective amnesia, and hallucinations . These different types of suggestions were characterized by Hilgard  as the domain of hypnosis.
Hypnotic experiences take place in the realm of imagination of the person under hypnosis . However, it is interesting to note that hypnotic mental imageries and ordinary ones do not have the same experiential qualities . Indeed, the construction of a mental imagery is both intentionally and consciously created, whereas imaginary experiences under hypnosis are generally involuntary . People are suggested or informed about an image and it naturally comes to them. This difference seems to be supported by the fact that neurocognitive activations differ from normal and hypnotic imaginary experiences . Another characteristic of hypnotic experiences, including the ideomotor ones, is that they are cognitive in nature . Indeed, participants simply experience alterations in cognitive processes such as perception and memory. People differ in their abilities to experience hypnosis and it might be that some hypnotic responses require specific underlying abilities that are not shared by everyone, or that many individual components might be needed to experience a hypnotic phenomenon . The ability to dissociate, cognitive flexibility, susceptibility to suggestions, fantasy proneness, and imaginative abilities were identified as possible traits that make an individual more amenable to experience hypnosis [33-36].
3. Theories of hypnosis
Hypnotic techniques became popular long before people knew what they were and how they worked. In the past, theorists viewed hypnosis as an altered state of consciousness or trance, but the quest to find evidence of this presumed state remained fruitless . Indeed, it was discovered that people can respond in a similar yet slightly diminished way to non-hypnotic suggestions, suggesting that hypnosis is just another normal experience . Moreover, since people under hypnosis are able to execute a full range of behaviours, theories needed to be able to encompass all of these aspects . Due to the failure to explain such phenomena, several theories of hypnosis were developed, such as the psychoanalytic theory, the reality-testing theory, and more recently, the cold control theory and the discrepancy-attribution theory [21, 37, 38]. However, toward the end of the 20th century, two theories stood out as the most researched and influential ones: the dissociative theory and the sociocognitive theory.
Dissociative theories were first developed based on speculations about links between hypnosis and the phenomenon of dissociation . Although a clear definition of dissociation is lacking, the first proponent of the dissociation theory described it as a split in the subunits of mental life, resulting in one or more parts left out from conscious awareness and voluntary control . The neodissociative theory, developed by Hilgard, posits that hypnotic behaviours are produced by a "division of consciousness into two or more parts"  in which “part of the attentive effort and planning may continue without any awareness of it all” (p.2, 40]. Additionally, these subsystems are coordinated by a higher-order executive system, the 'executive ego' . According to this theory, hypnosis alters the functioning of the executive ego, which tricks the mind about what is really going on. For example, when someone is asked to raise their arm under hypnosis, the executive ego might be responsible for the movement; however, because the awareness component of this has been separated into another part, this appears as an involuntary act to the hypnotised person .
Akin to dissociative theories, sociocognitive theories reject the idea that hypnosis requires an altered state of consciousness . In fact, the same individualized social and cognitive variables that shape complex social behaviours are thought to determine hypnotic responses and experiences . These variables are (a) a positive experience (attitudes, expectations, beliefs) with hypnosis in general, (b) good motivation to respond to suggestions, (c) clear indications that signal how to respond to hypnotic suggestions, and (d) implicit or explicit instructions in which to become absorbed or to imagine suggestions provided by the hypnotist. It is thought that when all of these variables are working together in a given individual, the person is under hypnosis . Moreover, sociocognitive theories state that responses under hypnosis are goal-directed and that hypnotised people continue to act according to their aims and values, just as they ordinarily behave according to a socialized role . Finally, rather than being attributed to an altered state of mind, the enhanced responses seen in people under hypnosis are merely a reflection of increased motivation and expectations .
Beyond differences and resulting controversy steaming from the dissociative and sociocognitive theory perspectives, new findings from psychophysiological and brain imaging studies have allowed the scientific community to support the hypothesis that experiences under hypnosis are "genuine" . Indeed, studies demonstrated that there are distinctive patterns of activation (anterior cingulate cortex and frontal cortical areas) attributable to hypnosis and that these patterns comprise mechanisms used in other familiar cognitive tasks (focused attention, imagination, absorption) [24, 31]. Furthermore, there are specific psychophysiological correlates for suggested experiences [24, 31]. Some studies demonstrated that there is a qualitative distinction between neurocognitive activations that occur when people are asked to imagine certain images under hypnosis and in ordinary conditions . Also, the hypnotic experiences appear to create brain states closer to the real experience, a phenomenon corroborated by the subjective reports of individuals . Finally, brain imaging and psychophysiological studies might also enrich our understanding of the respective contribution of the social context, the subject's aptitudes, expectations, and intrasubjective experience of hypnotic phenomena.
4. The clinical use of hypnosis
4.1. Medical conditions
4.1.1. Hypnosis alone
Thus far, the value of hypnosis has already been recognized for many physical and medical conditions. Indeed, in 1996, the National Institute of Health Technology Assessment Panel Report considered hypnosis as a viable and effective solution to treat pain associated with cancer and many other chronic pain conditions . It was even found that in certain conditions, the degree of analgesia resulting from hypnosis matched or even exceeded that provided by morphine . These findings are supported by the results of Montgomery, DuHamel, and Redd's meta-analytic review, which found that 75% of the people experienced pain reduction due to hypnosis, and these reductions were found in both a clinical and a healthy population. In their review of the literature, Neron and Stephenson  also present evidence on the effectiveness of hypnotherapy for emesis, analgesia, and anxiolysis in acute pain. Montgomery et al.  found that when compared to empathic listening, presurgery hypnosis was more effective in reducing pain intensity and pain unpleasantness for breast cancer patients. In addition to reducing the pain associated with cancer, hypnosis was also found to effectively reduce the affective morbidities (anxiety, discomfort, and emotional upset) associated with the medical procedures [46-48], as well as reduce fatigue [46, 49], sleep problems , nausea  and the quantity of medication needed . Similar results (reduction in pain, anxiety and medication and better satisfaction) were found for plastic surgery patients , severe burn care patients , women giving birth , breast biopsy patients  and patients undergoing dental procedures . Hypnosis also served as a sole anaesthetic ingredient for thousands of surgeries . Other medical conditions that have been found to be responsive to hypnosis are preoperative preparations for surgery, a subgroup of patients with asthma, dermatological disorders, irritable bowel syndrome, hemophillia, post-chemotherapy nausea and emesis (Pinnell & Covino(2000) cited in 43). Of note is that in the medical environment, clinical hypnosis is provided as an adjunct to medical treatment. There is usually no time for multiple sessions based on skills acquisition and homework. Intervention is often provided at bedside, or in preparation and during medical procedures away from the usual office-based psychotherapy setting. The goal of care is often symptom relief and comfort during the medical procedure and not psychological therapeutic change, which is typically the end point of psychotherapy. Hypnosis is used because it is efficacious but most importantly it is practical (short: minimal practice, no homework or assignments; portable: self-hypnosis) Flory & Lang provide examples and data supporting this type of hypnotic intervention used as a flexible and practical tool to alleviate pain, anxiety, and treatment side effects while potentially reducing the need for sedation and stabilizing the vital signs .
Flory & Lang provide examples and data supporting this type of hypnotic intervention used as a flexible and practical tool to alleviate pain, anxiety, and treatment side effects while potentially reducing the need for sedation and stabilizing the vital signs .
CBHAs an adjunct to CBT
Kirsch et al.  reported substantial effect sizes for problems such as weight loss, pain, anxiety, and insomnia. More specifically, it was found to be particularly effective for the treatment of obesity [15, 56]. Indeed, long-term weight loss was maintained at follow-ups, which is an issue for most people who gain their weight back soon after losing it . In their review of the literature, Chambless and Ollendick  even identified hypnosis (in conjunction with CBT) as an empirically supported therapy for obesity, along with headaches and irritable bowel syndrome . A study done with women suffering from chronic breast cancer pain revealed that cognitive hypnotherapy or CBH was effective not only in reducing pain, but also in decreasing pain over time as the cancer progressed . As for cigarette smoking, many studies assessing the use of hypnosis as an adjunct to cognitive-behavioural interventions found good results , with the rate of abstinence varying from 31 to 91% at the end of treatment and 31 to 87% around the three-four month follow-ups . However, these results should be interpreted with caution, as some research demonstrated considerable limitations such as the exclusive use of self-reports, small sample sizes, a lack of differentiation between hypnosis and relaxation techniques and no clear definition of cigarette smoking . More recently, some studies using more reliable approaches showed promising results in the use of hypnosis for cigarette smoking. Indeed, results indicate that after treatment, at three month, six month and 12 month follow-ups, more participants in the hypnosis group were abstinent [60, 61]. Rather than using CBH, these studies either compared hypnosis to behavioural treatment or to a waiting-list control group. Hypnosis appears to be a promising avenue for many physiological and psychological problems but most importantly, hypnosis is a cost-effective alternative procedure . However, as Schoenberger's review  indicates, more rigorous methodologies as well as more studies comparing specifically the added benefit of hypnosis to CBT are needed to determine its real effects.
4.2. Anxiety disorders
4.2.1. Social anxiety disorder
The essential feature of social anxiety disorder (SAD) or social phobia is an important and persistent fear or worry about social and performance situations . Social phobia can be divided into two types: generalized, in which individuals fear most social situations (e.g. having a conversation, facing authority, speaking in front of people and so on); and specific, when individuals only fear one particular situation (e.g. eating in front of people). According to different studies, the prevalence of SAD ranges from three to 13 % of the population. In their review of five meta-analyses that looked specifically at the treatment of SAD, Rodebaugh, Holaway, and Heimberg  found that CBT appears to provide benefits for adults diagnosed with SAD, with modest to large effect sizes when compared to waiting-list control, as well as moderate to large effect sizes from pre to post-treatment.
4.2.2. Specific phobias
A phobia is characterized by a marked and persistent fear prompted by the presence or anticipation of an encounter with a specific object or situation . This situation can create a sensation of panic, somatic manifestations of anxiety, fainting or even trigger a panic attack in the phobic person. According to the DSM-IV-TR , there are 5 subtypes of phobias: animal type, natural environment type, situational type, blood-injection-injury type, and other type, which includes all phobias that do not fit in the previous categories. The lifetime prevalence rate varies from 7.2 to 11.3%. CBT procedures (including in vivo-exposure and systematic desensitization) are considered the treatments of choice for specific phobias . Even though these techniques apply to most phobias, certain ones require specific adaptation such as the applied tension technique for blood-injury-injection phobias .
In order to render exposures less distressing, patients under hypnosis are suggested to imagine themselves in a magic bubble when they revisit their feared object or situation, which acts as a protection. During age regression, the person is guided back in time to a past experience in order to relive it, or the person can also be suggested to remember the experience in a here-and-now as vividly as possible .
In order to render exposures less distressing, patients under hypnosis are suggested to imagine themselves in a magic bubble when they revisit their feared object or situation, which acts as a protection.
During age regression, the person is guided back in time to a past experience in order to relive it, or the person can also be suggested to remember the experience in a here-and-now as vividly as possible .
4.2.3. Panic disorder with or without agoraphobia
The main feature of Panic Disorder with or without Agoraphobia (PD/A) is the presence of recurrent, unexpected panic attacks, accompanied by persistent concerns about having other panic attacks, worry about the possible implications or consequences of panic attacks, or a significant behavioural change related to the attacks . As for panic attacks, they are discrete periods of intense fear or discomfort that are accompanied by both physical and cognitive symptoms such as heart palpitations, hyperventilation, dizziness, a fear of losing control or going crazy, depersonalization and so on. People who suffer from PD sometimes develop agoraphobia, which is an anxiety related to being in places or situations in which escape might be difficult or impossible and help difficult to receive. In community samples, rates vary between one and two percent, although higher rates [3.5%) were found in some studies (75]. When treating PDA, both the Canadian Psychological Association (CPA) and the APA recognize CBT as the first line of treatment . Indeed, efficacious and robust treatment effects of this therapy have been verified across a variety of treatment settings for extended follow-up periods.
Hypnoanalysis is a mix of hypnosis and psychoanalytic techniques
Hypnoanalysis is a mix of hypnosis and psychoanalytic techniques
4.2.4. Generalized anxiety disorder
People who suffer from Generalized Anxiety Disorder (GAD) experience excessive and hardly controllable worry and anxiety most of the time. Contrary to some other anxiety disorders where the anxiety is focused on a specific event or thing (e.g. specific phobia), GAD individuals worry about different situations and activities. Many individuals also develop somatic symptoms such as muscle tension, nausea, and sweating. In community samples, approximately three percent of the population will develop GAD . As for the treatment of GAD, traditional narrative reviews and meta-analyses have consistently found that CBT and applied relaxation are the most efficacious treatments .
4.2.5. Obsessive-compulsive disorder
Obsessive-Compulsive Disorder’s (OCD) main features are recurrent obsessions and/or compulsions that are so severe that they are time-consuming and/or cause distress to the person. Obsessions may be persistent ideas, thoughts, impulses or images that can be related to many different topics such as contamination, religion, symmetry and repeated doubts. As for compulsions, they are repetitive behaviours or mental acts that people perform in order to diminish the anxiety associated with their obsessions. The estimated lifetime prevalence of OCD is 2.5% . In a recent review of the literature, Podea, Suciu, Suciu, and Ardelean  concluded that CBT is an effective treatment for OCD, that it is at least as effective as medication and that it demonstrates good benefits at follow-ups.
4.2.6. Post-traumatic stress disorder
In the DSM-IV-TR , PTSD is described as the development of characteristic symptoms after an individual is exposed to an extreme traumatic stressor (A1). The traumatic event must put at risk the physical integrity of the individual or others and the person's response must involve intense fear, helplessness, or horror (A2). The characteristic symptoms of PTSD include (B) stress and hyperarousal, (C) persistent avoidance of situations or reminders of the trauma and (D) vivid experiences of being back in the midst of the traumatic event, which are often referred to as a
Among all of the anxiety disorders, the addition of hypnosis to CBT in the treatment of PTSD is the most studied. This interest has been triggered by factors such as the evidence that PTSD patients seem to be more highly hypnotisable when compared to the general population and other patient populations [96-98]. Butler, Duran, Jasiukaitis, Koopman et al.  developed a diathesis-stress model of dissociation to explain this phenomenon which is that "highly hypnotisable/dissociative people would be more likely to develop posttraumatic/dissociative conditions rather than other psychiatric conditions". Evidence in support of this model are the fact that higher scores on hypnotisability scales are associated with avoidance symptoms, which is a core aspect of PTSD  as well as with better therapeutic success . However, research is needed to exclude the possibility that it is the development and maintenance of PTSD that create a state of high hypnotisability. Moreover, clinical findings seem to suggest that there is a similarity in phenomenology between PTSD symptoms and the experience of hypnosis . For example, during hypnosis, the person is entirely focused and absorbed into the suggestions and this absorption is also evidenced in PTSD sufferers, who sometimes focus so intensely on their traumatic memories that they are able to create physical and emotional responses. Another common factor is the phenomenon of dissociation, which can occur both during and after the trauma. Finally, both PTSD and hypnosis are experiences in which the person is hyper-responsive to both their environment (social, physical cues) and internal cues . Because traditional interventions are mostly aimed at targeting the core symptoms of PTSD, the interest in hypnosis was also prompted by the fact that as a flexible form of treatment, it might be able to target important symptoms such as sleep and dream disturbance, pain, and emotional and anxiety withdrawal problems associated with traumas [100, 102].
As part of their symptoms, PTSD sufferers often complain about sleep problems . Some studies indicated that hypnosis can be helpful in reducing time to sleep onset in a group of individuals with chronic insomnia [104, 105]. A meta-analysis of 59 outcome studies also demonstrated that the short-term effects of hypnosis (one-two months) and relaxation training were comparable to the effects of short-term drug therapy and that the long-term outcomes even surpassed the drug therapy in certain instances . Abramowitz, Barak, Ben-Avi, and Knobler  studied a group of chronic combat-related PTSD sufferers who experienced sleep problems even though they received supportive therapy and serotonin reuptake inhibitors (SSRIs). The participants had difficulty falling asleep as well as maintaining sleep and reported night terrors. The authors compared the efficacy of two weeks of one-and-a-half hour hypnotherapy sessions with the drug therapy Zolpidem to see the effects on PTSD symptoms and sleep problems. They found that in addition to see a reduction in the major PTSD symptoms, the hypnotic group reported better sleep quality, fewer awakenings, and less morning sleepiness.
results for 3 year follow-up.
results for 3 year follow-up.
Recently, a new hypnotic technique called hypnotherapeutic olfactory conditioning (HOC) showed promising potential in the treatment of PTSD. Based on CBT protocols, HOC is a technique that helps patients create new olfactory associations in order to surmount anxieties and dissociative states . More precisely, it is the "development, under hypnosis, of a positive olfactory association which allows the patient to regain control of their symptoms, especially when they were created by olfactory stimuli" (p.317 102). This technique is based on the notion that the sense of smell has the ability to create vivid memories due to the particular position of the olfactory bulb in the brain . In an exploratory study of three individuals suffering from needle phobia, panic disorder and PTSD respectively, Abramowitz and Lichtenberg  found a marked reduction in the symptoms, as attested by the rating scales and reduction in the use of medication. In a prospective study testing HOC with 36 patients suffering from chronic PTSD, results demonstrated significant reductions in symptoms, as assessed by the Impact of Events Scale (IES–R), Beck Depression Inventory, and Dissociative Experiences Scale . The gains were maintained at six month and one year follow-ups. In this study, the authors did not compare the direct added benefits of HOC to standard protocols. However, the fact that most patients had already been in therapy for a mean time of more than two years and that baseline symptoms presented significant psychopathology indicates that HOC was able to provide additional benefits to the therapy. Still, replication studies are needed for HOC.
4.2.7. Other anxiety-related problems
A study comparing the effects of two hypnotic procedures (imagery and cognitive restructuring under hypnosis versus hypnotic induction only) with two control groups (attention placebo and no treatment) on the treatment of test anxiety supports the idea that the combination of hypnosis and CBT offers more therapeutic gains . Indeed, results indicate that while the induction-only group had more improvements than the two control groups, only the group receiving imagery and cognitive restructuring under hypnosis obtained significant results on anxiety and academic performance .
4.2.8. Summary and conclusions on the clinical use of hypnosis
|Social anxiety disorder||Good outcomes|
|Significant reduction in anxiety at post-test and superiority of hypnosis at six-month follow-ups ||CBH more efficacious than CBT alone|
|Specific phobias||Mixed results|
|CBH and HOC as an effective treatment|
|Significance was reached in the Llobet study  but not in the Stanton study ||CBH provided better results than CBT alone  HOC allowed patient to face the phobic situation with success |
|Panic disorder with or without agoraphobia||Generally good results|
|Only based on case studies and reports. Intensity of episodes is reduced while other patients are panic-free||No superiority of CBH compared to CBT in one study, but patients received both treatments in a cross-over design, which limits the conclusions |
Effective relief of symptoms found in other studies [81-82]
|Generalized anxiety disorder||Good outcomes|
|Hypnosis as effective as CBT (no randomization)||Most patients in hypnosis and CBT group obtained anxiety scores below the normative ranges at post-test |
|Obsessive-compulsive disorder||Not applicable||Good results|
|Based on case reports|
|Post traumatic stress disorder||Good outcomes|
|Statistically significant reduction in hyperarousal symptoms but results did not reach clinical significance |
Hypnosis effective for treating sleep problems [104-105] and equivalent or better than drugs [106-107]
|CBH superior to CBT and other techniques on some measures [120-121]|
HOC found to be effective in reducing symptoms at post-test  and six-month follow-ups 
|Other anxiety-related problems||Mixed results|
|Improvement but no indication that hypnosis as a sole treatment is more efficacious than other methods or no treatment, except for one study . Superiority only stood out at one-month follow-up in another study ||Superiority of CBH over hypnosis alone and control groups|
To date, except for PTSD, there is a very small number of randomized controlled studies assessing the impact of CBH for the treatment of anxiety disorders, which limits the conclusions that can be drawn about its external validity. However, the results presented above still indicate that CBH is a promising treatment modality. Indeed, in addition to demonstrating its efficacy as a complete intervention to reduce anxiety symptoms, all studies that compared the additive effect of hypnosis found positive results, except for one. As stated before, this study used a cross-over design which might explain the lack of superiority for the combined group (exposure and hypnosis). Also, Mellinger  and Scrignar  reported the success of hypnosis as a valuable adjunct to render exposure practices more viable. Finally, using non-leading methods, Degun-Mather  reported the successful use of hypnosis to transform the fragmented memories of a war veteran who suffered from chronic PTSD and dissociative fugues into a complete narrative, leading to re-appraisal and re-structuring of the trauma. As for the evidence supporting hypnosis as a stand-alone treatment, results are mixed. Indeed, some of the case reports and studies presented above found positive results [21, 27]. On the other hand, in 2003, the STEER  looked at four randomized controlled trials of hypnotherapy as a sole therapy for anxiety, coming to the conclusion that there was insufficient evidence regarding the efficacy of hypnotherapy and that it did not appear to be more effective than other treatments. In their conclusion, the authors of the STEER report also mentioned that the general quality of all studies was unsatisfactory. All of them presented major methodological flaws, such as a lack of established questionnaires, no use of imagery or suggestions during hypnosis, small sample sizes and no clear indications of qualification of competence of the therapists. This again renders it difficult to draw firm conclusions. More recently, a systematic review of controlled trial studies revealed that hypnosis as a sole treatment for anxiety was not superior than control conditions (waiting list controls, contact controls, or other non-standard treatments) , and though it is a powerful supportive tool, using it as a therapy by itself is an error . Research on clinical hypnosis should reflect the clinical practice in psychotherapy,  and thus hypnosis should be viewed and studied as an adjunct to commonly used and recognized techniques. In fact, hypnotic technique can directly reinforce CBT strategies by helping patients to control and regulate the anxiety as well as the cognitive and attentional processes characteristic of many anxiety disorders . One point to note, however, is that the boundaries between hypnosis as a stand-alone treatment and as an adjunct are sometimes unclear, as some people view a hypnotic induction followed by suggestions as CBT in itself . For a summary table of the data presented above, see table 1.
5. Guidelines and benefits of the application of hypnosis to CBT protocols
5.1. How to integrate hypnosis to CBT components
As a psychosocial treatment, CBT has roots in both the cognitive and behavioural traditions and is based on the idea that our thoughts influence our feelings and behaviours . Important components of CBT include relaxation training, exposure (both imaginal and in-vivo), cognitive restructuring, the building of coping skills, ego-strengthening, and self-efficacy. In the following, based on what several authors described (William, Bryant, Lynn and colleagues, Alladin, Degun-Mather), we will report a summary of how hypnosis can enhance each of these components [6, 16, 17, 23, 119]
In the treatment of PTSD, for example, this technique involves the projection of different images of memories of the trauma on one side of an imagined screen, and on the other side something that comfort the person .
In the treatment of PTSD, for example, this technique involves the projection of different images of memories of the trauma on one side of an imagined screen, and on the other side something that comfort the person .
Another coping skill that patients can acquire is to learn to redirect their attention away from distressing cues. For example, in PTSD, arousal and avoidant symptoms are triggered by both internal and external cues associated with the memories of the trauma. Unfortunately, PTSD patients seem to be particularly distractible to these cues and the result is that their condition cannot improve. Lynn et al.  propose that hypnosis can facilitate attention control in these patients so that they can stop being absorbed by cues of traumatic memories. Indeed, they propose that if it is possible to suggest to a patient to enter a state of hypnosis, it is possible to suggest that this same patient experiences enhanced attention and concentration (p.322). Thus, people under hypnosis can learn not only how to focus their attention in the moment, but also how to switch their attention away from increasingly distracting cues . The latter hypnotic attentional control learning can also be useful to help patients contend with their flashbacks . However, Lynn et al.  also propose that this technique should also be accompanied with suggestions for increased tolerance to disturbing flashbacks.
5.2. Hypnotisability assessment
Different opinions remain as to whether or not levels of hypnotisability should be assessed before undergoing hypnotherapy . These divergent opinions are based among other things, by the fact that some studies do report a link between levels of hypnotisability and treatment gains [102, 103] while others do not [121, 146, 147]. Moreover, researchers are facing some difficulties when trying to link hypnotisability with treatment outcomes. Indeed, one problem lies in the timing of the assessment . When participants undergo a standard test of hypnotisability prior to their treatment, they are likely to infer conclusions about their own susceptibility to hypnosis. This could, in turn, influence their expectations toward the success of the treatment, which could ultimately affect their treatment outcome . On the other hand, when hypnotisability levels are assessed after the treatment, the participants' experience during the treatment might then have an influence on subsequent levels of responsiveness under hypnosis . On a more positive note, Lynn and Shindler  state that modern evaluation techniques have rendered possible the use of a good hypnotisability assessment. They also present the advantage of being able to evaluate a variety of factors (attitudes, beliefs, rapport with therapist, motivation to respond) that could influence the response to hypnosis, and to model the hypnotherapy techniques around it in order to augment the efficacy of the treatment . Indeed, as it was stated before, considering participants' attitudes and expectations of hypnosis is crucial, as expectation of positive therapeutic outcome is more often than not predictive of improvement in treatment . In term of hypnotisability levels displayed by participants, expectancies have also been demonstrated to play a major role . Moreover, a good assessment is imperative to remove clients who are unsuitable candidates for hypnotherapy due to their conditions (e.g. patients who are more prone to psychotic decompensation, those with a paranoid level of resistance to being controlled) . Needless to say, this evaluation goes beyond the simple use of formal scales of hypnotisability . For guidelines on how to assess patients' level of hypnotisability, refer to Lynn and Shindler .
5.3. Research on hypnosis
There remains a long way to go before hypnosis as an adjunct to the treatment of anxiety disorders is considered a first-line treatment. Future research will need to conduct good quality randomized controlled trials for each of the anxiety disorders. Well-conducted multiple case studies from independent researchers also must be done to establish the validity of hypnosis as an adjunct to CBT. Studies must have adequate sample sizes so that good power can be achieved, and provide an intent-to-treat analysis in order to have better chances of finding conclusive results. They also need to have a clear detailed protocol for the hypnotic techniques used, for replication purposes. Moreover, as suggested by Lynn et al. , good descriptions of the population at hand permit replication and help in assessing the external validity of the results. Such descriptions should include the diagnostic procedures, patients' demographic and treatment history, use of medication, comorbid diagnoses, and tests administered . According to Schoengerber , despite the difficulties met while assessing hypnotisability levels, good attempts should be made to do so. For example, the Stanford Hypnotic Susceptibility Scale-Form C (SHSSC) is considered a gold standard measure and a good individual measure, and the Waterloo adaptation of this scale, the WGSC, is good for group administration . Furthermore, in order to avoid the possibility that disproportionate numbers of high hypnotisable participants end up in one group compared to another, researchers could randomly match or stratify participants in terms of their hypnotisability scores or at least report the hypnotic suggestibility of each group in terms of scores. These scores could then be used as covariates in statistical analyses if groups differ considerably on this variable . As some studies seemed to indicate that the effect of adding hypnosis appeared or persisted in the long-term [15, 126], studies should include follow-up measures. In conclusion, in accordance with the Society for Clinical and Experimental Hypnosis, this chapter argues that hypnosis is a technique and not a type of therapy and that it should be used as a tool to augment the efficacy as well as the patients' understanding of CBT principles [43, 134].
Clinical hypnosis is a flourishing area of research that has so far demonstrated the usefulness of hypnosis in many domains, especially in the treatment of pain in the medical environment and during medical procedures . According to Bryant , there is no doubt that hypnosis can ameliorate established means of treating anxiety disorders. However, more research needs to be conducted in order to provide the information necessary to establish hypnosis (added to CBT) as an empirically supported treatment for anxiety disorders. The lack of adequate studies on this topic points to the need for more rigorous randomized controlled investigations on the use of hypnosis for anxiety disorders. This chapter, as well as many other books and articles [16, 23, 94, 150] present many ways in which hypnosis can be added to CBT. Researchers who wish to study hypnosis can refer to these as guidelines.
William  pointed out that hypnotherapy does not need to prove that it is superior to other forms of treatment in order to have clinical value. Indeed, the goal of clinical psychology is to determine what treatments are working for which patients with which problems, and under what conditions (Lazarus, 1973; cited in 6). Moreover, as stated before, hypnosis is a very cost-effective method  that could represent in some cases, a rapid, non-addictive and safe substitute to the use of medication, which is particularly important given the current increase in health care costs and adverse economic conditions . Another advantage of hypnotherapy is that it can be used easily outside the clinic under the form of self-hypnosis. Self-hypnosis is defined as the employment of hypnotic suggestions through self-talk or listening to a recording of hypnotic suggestions . Contrary to popular belief, how intensely someone responds to hypnosis resides in the ability of the individual, rather than in the special skills of the hypnotist . Thus, self-hypnosis is a viable solution to help maintain the skills that were acquired during therapy. Consequently, hypnosis seems to respect the principle of parsimony, one of the most popular principles of clinical psychology, by creating more rapid gains and enhancing the efficacy of CBT interventions. Indeed, clinical psychologists should always try to utilize the least complex and most efficacious mode of treatment first .
This chapter focused on the use of hypnosis in the treatment of adult anxiety disorders. It is important to note that hypnosis is a therapeutic tool that is suitable for child and adolescent therapy. Indeed, although most research on hypnosis focus on adults, the popularity of complementary and alternative forms of therapies has started to attract parents of children with different problems . According to Saadat and Kain , hypnosis is a suitable therapy for children because in general, they are more hypnotisable than adults. This is thought to be due to their increased capacity and willingness to become absorbed in fantasy, play, and imagination . Moreover, psychologists can easily design specific hypnosis goals and suggestions that are individualized to the child and respect a developmental psychopathology perspective . As for adults, meta-analyses and overviews have demonstrated the efficacy of hypnotherapy in treating children medical conditions such as asthma, chronic and acute pain, along with procedure-related distress for cancer patients . Hypnosis also has improved child behavioural conditions such as trichotillomania, thumb-sucking, enuresis, dysphasia and chronic dyspnea . However, Huynh et al’s.  review of the literature revealed no randomised or controlled trials on the use of hypnotherapy for children with psychiatric disorders. Still, a high number of case reports indicated that hypnotherapy can be useful in treating children with PDA, social and specific phobias, OCD, GAD, and PTSD . However, as is the case for adult anxiety disorders, the addition of hypnosis to clinical practice for children and adolescents needs to be developed and studied further before it is recognized as an empirically supported treatment.
- Flory & Lang provide examples and data supporting this type of hypnotic intervention used as a flexible and practical tool to alleviate pain, anxiety, and treatment side effects while potentially reducing the need for sedation and stabilizing the vital signs .
- In order to render exposures less distressing, patients under hypnosis are suggested to imagine themselves in a magic bubble when they revisit their feared object or situation, which acts as a protection.
- During age regression, the person is guided back in time to a past experience in order to relive it, or the person can also be suggested to remember the experience in a here-and-now as vividly as possible .
- Hypnoanalysis is a mix of hypnosis and psychoanalytic techniques
- results for 3 year follow-up.
- In the treatment of PTSD, for example, this technique involves the projection of different images of memories of the trauma on one side of an imagined screen, and on the other side something that comfort the person .