Compared to the healthy volunteers, the patients scored higher on all PERM scales, and possessed higher passing rates on SHSSC Dream and Posthypnotic amnesia. In the patients, some SHSSC items were significantly correlated with the PERM scales. However, the adjusted R²s of these correlations were relatively low in both groups, suggesting that the correlation between hypnotic susceptibility and the functioning styles of personality disorder was weak. In some patients, the weak correlation might be due to their subconscious defense to hypnosis. As noticed earlier [18
], when facing the examiner, participants would be sensitive to the potential threat to the ego and would mobilize their defense mechanisms. The pronounced correlation in patients might indicate that hypnotic susceptibility influences the expression of personality disorders.
The higher passing rates of SHSSC Dream and Posthypnotic amnesia, two cognition related items in our patients, were similar to a previous investigation which showed that people with mixed personality disorders had higher hypnotic susceptibility [7
]. Specifically, the higher SHSSC Dream passing rate might help us to understand the prevalence of hallucination in personality disorders [19
], and some scholars attributed Hypnotic amnesia to the conscious suppression of memory due to a defense mechanism [20
], which might be particularly the case in patients with personality disorders who had traumatic experiences [21
]. Consequently, the present results helped to understand the prevalence of hallucination and memory deficit in personality disorders [22
Regarding hallucination in personality disorders, the borderline type would be a particular example. In our patients, PERM Borderline style was positively correlated with SHSSC Taste. This correlation might indicate that patients with borderline personality disorder features were prone to hallucination and to the autistic fantasy defense [23
]. Indeed, the borderline personality disorder is commonly associated with hallucination [24
], but this phenomenon was once overlooked [25
According to one theoretic interpretation of hypnosis, Posthypnotic amnesia occurs because the forgotten materials are dissociated from awareness, and it denotes the most deteriorated stage of dissociation [20
]. When referring to the Schizoid personality disorder, patients are likely to pay little attention to how they behave, or how their behavior may or may not impress the experimenter [26
]. Consequently, they might easily forget the experience obtained during the experiment. Moreover, with reversibility as an essential mark, Posthypnotic amnesia is somewhat like the temporarily retrograde amnesia. Studies have consistently reported the retrograde amnesias in patients with impairment in the frontal lobe [27
]. Meanwhile, the schizoid personality disorder patients also displayed neuropsychological malfunctions in relation to the frontal lobe [28
]. This might be a possible mechanism behind the correlation between the PERM Schizoid and the SHSSC Posthypnotic amnesia in our patients.
On the other hand, patients with narcissistic personality disorder requiring excessive admiration from others, are likely to participate in tasks which merit special talents, to display a strong intense reaction to perceived threats to self-esteem, are sensitive to criticism, and are known to be active and flamboyant [29
]. Therefore, they might be particularly interested in what the experimenter had ordered, and in how their actions may impress the experimenter. This could be particularly likely when they are asked to recall the details of the experiment. Thereupon, lower SHSSC Posthypnotic amnesia would be correlated with the higher PERM Narcissistic style in patients with personality disorders.
Nonetheless, several limitations of the present study design are noted. We used the Chinese version of SHSSC which has not yet been validated. We did not divide our personality disorder patients into individual types, and the age spans of our participants were narrow. In addition, Axis I disorders such as anxiety, depression and sleep disorders were not included in the present study. Furthermore, we found correlations (predictions) which were in one direction only, and these correlations in both our groups were low. Nevertheless, our findings could help to explain the psychotic features in personality disorders such as hallucination and memory distortion, and support the use of Psychoanalytic therapy in this pathology, regardless of its intractability [30
]. It has also been shown that the hypnotic technique in particular could reduce a half treatment course for personality disorders [31
]. Although the defense mechanism of a participant is constant [18
], our findings imply at least that a memory retrieval may help to normalize the functioning style of Schizoid personality disorder, while an external negative experience (e.g., ammonia) exposure may help to normalize the style of the Borderline disorder.