Pilot Study on Classification of Sensory Symptoms in PTSD

Abstract

PTSD treatment that focused on a sensory symptoms is increasing. The study aimed to explore symptoms and abnormalities in the five senses exhibited by persons with PTSD and to examine whether there are any differences depending on type of traumatic experience. Questionnaire was followed by interviews to clinical psychologists involved in the treatment of PTSD. 249 PTSD symptoms exhibited in the sensory organs were collected. Sensory symptoms were classified into three categories according to the type of symptoms and the type of traumatic events. Cluster 1 is a group formed by child abuse and violence together with audition, tactile, and hyperarousal. Cluster 2 is made up of natural disaster, accident, and sexual assault together with vision, olfaction and intrusion. Cluster 3 is made up of multiple traumas together with gustation and dissociation. It is speculated that the survivors of Child abuse and violence are hypersensitive to sounds, the presence of others, and physical contact because they try to quickly sense when a perpetrator is approaching. Natural disasters, accidents, and sexual assault are events with strong smell and severe visual impact, it is possible that they may easily cause reliving of the event in the form of shocking visual images and smells in flashbacks. Dissociation symptoms were related with complex trauma and taste. The mouth is the site of first contact between mother and child, and it is possible that gustatory dissociation may occur mainly in cases of severe and repeated trauma since early childhood.

Post-traumatic stress disorder (PTSD) is a psychiatric disorder that can develop after direct or indirect exposure to a very threatening or frightening event such as death, fear of death, serious injury, or sexual violence (American Psychiatric Association, 2013). Traumatic stress experiences can range from natural disasters, car accidents, terrorism, war/combat, rape, and abuse. The core symptoms of PTSD as described in DSM5 (APA, 2013) are: 1) intrusive symptoms associated with the traumatic event(s) after the event(s),including recurrent distressing memories, recurring nightmares and flashbacks; 2) avoidance of stimuli associated with the trauma, including internal reminders, such as distressing memories and thoughts about the trauma, and avoidance of distressing external reminders, such as people, places, conversations, and activities that remind us of the trauma;3) Negative changes in mood and cognition, including exaggerated negative thoughts about self, others, and the world; persistent negative emotional states such as fear, terror, anger, guilt, and shame;4)Alterations in arousal and reactivity, including irritability and angry outbursts with little or no provocation, reckless and self-destructive behavior, hypervigilance, exaggerated startle response, problems with concentration, and difficulty sleeping. In the fifth edition of the DSM, dissociative symptoms, such as depersonalization and derealization, were added as subtypes. In addition to these core symptoms, individuals with PTSD may experience behavioral problems such as suicide attempts, self-injury, substance abuse, and eating disorders; somatic complaints such as unexplained pain; and dysesthesia symptoms. Thus, PTSD symptoms and problems can manifest in a variety of ways in diverse functions, including cognition, memory, emotion, behavior, and sensation.

A number of evidence-based treatment approaches are currently being developed for this broad range of PTSD symptoms. These approaches vary in their underlying theories and intervention techniques. However, many treatments have in common that they consist of three therapeutic phases: safety and stabilization, reconstruction of psychological traumatic memories, and reintegration of memory and personality which include consolidation of treatment gains to transition from end of treatment to engagement in relationships, work or education, and community life. In addition, the second phase, reconstruction of psychological traumatic memories, is common to many therapies as a major phase of treatment (Herman, 1992; Van der Kolk et al, 1996, 2006).

How traumatic events are stored is an important issue for subsequent therapeutic intervention because it is directly related to the trauma survivor's distress and resulting symptoms. No single factor can be identified for trauma memory, as it involves not only cognition and thought, but also a variety of emotions and bodily sensations. However, early evidence-based approaches to PTSD focused primarily on cognitive approaches as memory and information processing of trauma. Foa and colleagues developed Prolong-Exposure (PE) based on the emotional processing theory (Foa & Kozak, 1986), which states that memories of traumatic events are recoded under conditions of extreme distress and that information processing is impaired. Emotional processing theory suggests that PTSD manifests itself through the development of a fear network of memories that induce escape and avoidance behaviors and require modification of the fear structure (Foa et al., 1989). Cognitive processing therapy (CPT) (Reisick & Schnicke, 1993) focuses on the cognitive aspect of correcting cognitive distortions in memories of traumatic events. Thus, the early treatments developed for PTSD were primarily cognitive aspect interventions. On the other hand, Eye Movement Desensitization and Reprocessing (EMDR) is a method that incorporates the sensory and physical aspects of traumatic memories into the treatment approach while focusing on the cognitive aspects. EMDR is based on the adaptive information processing model that reduces the emotional load associated with traumatic memories, modifies the negative self that stagnates in the brain, and reintroduces the disappearance of unpleasant physical sensations. In this method, not only cognitive but also sensory and physical aspects are emphasized. For example, alternative bilateral sensory stimulation such as visual, auditory, and tactile stimulation is added to traumatic memory recall to promote reconstruction of the traumatic memory, and the sensory and physical reactions to the activation of the traumatic memory are monitored through body scans.

However, clinical research on the sensory aspects of PTSD is not as extensive as that on cognition. Baek et al. (2019) demonstrated fear suppression by showing that alternate bilateral sensory stimulation persistently increased superior colliculus and mediodorsal activity in a mouse experiment, thereby advancing our understanding of EMDR mechanisms. However, there is still a lack of knowledge about the mechanism of the therapeutic effects of EMDR in humans. Similarly, our knowledge of the efficacy of treatments that focus on the sensory aspects of PTSD is also lacking. In recent years, more attention has been paid to the sensory and physical aspects of traumatic memories, such as how people experienced the traumatic event through their five senses and how they experienced it on a physical level, and more clinical research on the sensory aspects of PTSD is needed.

To date, however, clinical research on the sensory aspects of PTSD in humans is not as extensive as that on cognition and is still in the process of development. In addition, most current PTSD research on the senses is basic research examining the relationship between specific sensory organs and specific symptoms. As for PTSD symptoms experienced visually, there are many reports of intrusive symptoms (Ehlers & Steil, 1995; Ehlers et al., 2002; Mellman & Davis, 1985). Ehlers et al. (2002) showed that 97% of survivors of childhood sexual abuse experienced visual intrusions. Moreover, the Dissociative Experiences Scale (DES; Bernstein & Putnam, 1986) includes many items for visual experiences, such as " feeling as though they are standing next to themselves or watching themselves do something and they actually see themselves as if they were looking at another person" and" the feel as if they are looking at the world through a fog, so that people and objects appear far away or unclear," suggesting that dissociative symptoms may also occur visually.

Furthermore, some experimental studies with veterans have referred to reduced visual exploration abilities in PTSD individuals (Aase et al., 2017; Olatunji & Fan, 2015). At the same time, regarding PTSD symptoms related to auditory, many studies have pointed out auditory hypervigilance, while others have also suggested high frequencies of auditory hallucinations (Alsawy et al., 2015; Crompton et al., 2017) and tinnitus (Clifford et al., 2019; Fagelson, 2007; Swan et al., 2017).There has been a recent increase in PTSD studies on olfaction. Olfaction has always been intimately related to emotion and memory, and basic research has shown so-called Proustian phenomena, where smells sometimes cause the spontaneous recollection of extremely distant autobiographical memories (Chu & Downes, 2000, 2002; Larsson & Willander, 2009). In the field of PTSD, it has been pointed out that flashbacks especially can be caused by olfactory clues (Kline & Rausch, 1985; Vermetten & Bremner, 2003). Certain smells can easily call to mind emotional memories of anxiety and fear in persons with PTSD, and surveys involving veterans have shown that PTSD groups exhibit more vivid reactions to smells from the battlefield, such as burnt rubber, than do non-PTSD groups (Wilkerson et al., 2018).Moreover, studies on tactile and cutaneous sensations have pointed out a correlation between PTSD and somatic disorders, such as chronic pain or pain hypersensitivity with no apparent physical cause (Defrin et al., 2008), as well as converse symptoms of reduced somatic sensitivity (Bernstein et al., 1986) or physical discomfort, such as feeling that one’s own body is made out of rubber (Gupta et al., 2017). In the field of dermatologic symptoms, some studies have pointed out the association of PTSD and specific dermatologic conditions, such as Urticaria、Pruritus, Herpesvirus infections and atopic dermatitis (Chung et al., 2010; Gupta & Gupta, 2000; Gupta et al., 2017). There is little PTSD-related research on gustation, but it has been reported that people with PTSD are more prone to taste disorders (Nin et al., 2017; Sakaguchi et al., 2013).

Thus, when examining the symptoms of PTSD individuals from the perspective of each sensory organ, there are various reports of symptoms other than those that are diagnostic criteria in the DSM5, and it also appears that there are differences in the way symptoms are presented by each sensory organ. At present, however, most studies on sensory symptoms in PTSD have looked at specific symptoms in PTSD individuals in relation to specific senses (e.g., vision and intrusion, auditory and hypersensitivity), and few have compared symptoms among all five senses. One of the few studies in that area is that of Hackman et al. (2004) and Ehlers et al. (2002), who compared intrusion symptoms exhibited by different sensory organs and noted that intrusion symptoms were more prevalent in vision than in the sensory organs. They compared the intrusion symptoms shown by the different sensory organs and noted that there were more intrusion symptoms in vision than in the sensory organs.

Since sensory organs are associated with the input of information, symptoms experienced as sensory abnormalities not only pose a strong threat to people with PTSD but can also interfere with their lives. Many of the symptoms experienced as sensory abnormalities, such as inability to taste, color, or hear, are difficult to self-regulate and can reduce self-control, self-confidence, and current quality of life, further compromising current adaptive skills. Moreover, because these sensory symptoms are not explicitly listed in diagnostic criteria such as the DSM-5, people with PTSD may avoid expressing their sensory symptoms because they believe they are unique to themselves, and the symptoms may persist without treatment. In addition, because sensory symptoms are difficult to explain or verbalize, they may be left untreated for a long time as "unknown symptoms. This study examines PTSD symptoms in the "sensory organs," which are often associated with life stress and are likely to cause secondary symptoms but are not yet fully understood.

Much of the research on PTSD symptoms is based on self-administered questionnaires, interviews, experimental studies, and meta-analyses with persons with PTSD. However, it is not always easy for PTSD individuals to objectively identify or verbalize their symptoms in the early stages of treatment. This is especially true when symptoms appear in the sensory organs. Therefore, prior to surveying PTSD individuals, this study first conducted a survey by interviewing PTSD therapists. Furthermore, most studies of sensory-organ symptoms of PTSD have focused on veterans, and few empirical studies have been conducted with survivors of other types of trauma. In recent years, however, an increasing number of studies have examined differences in symptoms due to different types of trauma experiences (Benfer et al., 2018; Cloitre et al., 2009; Guina et al., 2018; Smith et al., 2016) Therefore, this study also focused on whether sensory symptoms differ by trauma experience.The study interviewed PTSD therapists and asked them about symptoms and abnormalities in the five senses (vision, auditory, olfaction, tactile and cutaneous sensations, and gustation) of PTSD patients they treated, and compared which sensory organs were more likely to experience which symptoms. In addition, differences in the types of traumatic experiences were also examined. However, since the survey was conducted on PTSD therapists, care was taken to ensure that the content of the survey did not violate professional or research ethics.The purpose of this study was to explore what sensory symptoms PTSD individuals exhibit in clinical and daily life situations, to inform subsequent investigations of PTSD individuals, and to make recommendations regarding treatment methods.

Methods

Participants

Eleven clinical psychologists involved in PTSD treatment and support. All graduated from a two-year master's degree program in psychology or human sciences and are licensed as clinical psychologists in Japan. All were psychologists working full- or part-time at medical institutions that are visited by many PTSD patients, and all were using EMDR, PE, or CPT or were trained in these methods (3 males and 8 females). All participants were required to have at least two years of experience treating PTSD patients. The mean age of the participants was 41.73 years (SD = 9.49), range 7–57 years, and their PTSD treatment experience was 9.32 years (SD = 6.27), range 2.5–22 years.

Procedure

Participants were recruited from psychologists at several medical institutions in each region. The purpose, methods, and protection of personal information of the study were explained in advance, and only those who gave their consent were allowed to participate in the study. A questionnaire was first administered to those who consented to the study. The questionnaire was given to them in person or by mail, and they were asked to fill it out. The questionnaire consisted of the following items. (1) experience in treating PTSD, (2) whether or not the patient had symptoms that manifested themselves in the five senses (vision, auditory, olfaction, tactile and cutaneous sensations, and gustation) when treating PTSD patients, (3) details of the symptoms, and (4) the type of traumatic experience (sexual assault, child abuse, domestic violence, bullying, natural disaster, traffic accident, etc.) in which the patient presented these symptoms.

Next, a semi-structured interview survey was conducted based on the questionnaire. The location of the interview survey was in a private room at the participant's workplace. The researcher visited the participants' psychological workplaces and, with the permission of the head of each facility, conducted the interviews in the private rooms after work. During the semi-structured interview, the researcher asked the participants about the questions asked beforehand, particularly (2) any encounters with symptoms that appeared in the five senses ( vision, auditory, olfaction, tactile and cutaneous sensations, and gustation)in the treatment of PTSD patients, and (3) specific symptoms of the particular client who presented them. Interviews lasted 30–60 min. The study period ran from October 2015 to March 2016. Information was collected through questionnaires and semi-structured interviews, taking care not to include any content that could identify individual patients, so as not to violate the professional ethics of not divulging information obtained by clinical support professionals during treatment. In addition, this study was conducted with the approval of the Research Ethics Committee of the Graduate School of Human Sciences, University of Tsukuba (No 27–29).

Results

Relationship Between PTSD Events and Sensory Symptoms

A total of 249 PTSD symptoms appearing in sensory organs were collected from interviews with 11 PTSD therapists (Table 1). Furthermore, in cases where symptoms were seen in several sensory organs, each was treated as one symptom. For example, "Images of the traffic accident appear as flashbacks. Suddenly, I see a car coming toward me and hear the sound of emergency braking clearly." episodes were counted as one visual intrusion and one auditory intrusion. The percentages of symptoms in parentheses below were calculated using a total of 249 symptoms as the denominator.

Table 1.

The sensory symptoms of PTSD

Sensory	Symptoms	Contents	frequency
Vision (88)	Dissociation (23)	Abnormal perception. “see something strange.”	2
		Visual hallucination.”see the thing which does not exist."	2
		Abnormal color perception. “color blindness”,“lose colors”	2
		Abnormal size perception “looks distorted “,“the world seems to stretch”	4
		Abnormal distance perception.”Switch to overhead view “,”perspective confusion “	3
		Abnormal contour (form) perception.”Looks blurry “	6
		Lack of reality. “seems to see the world through the veil.”, ” not real”	4
	Hyperarousal (15)	Hyperarousal → Avoidance behavior	12
		Hyperarousal only	3
	Intrusion (50)	Part of person/face	15
		Part of place	7
		Situation (still image)	7
		Situation (moving image)	21
Olfaction (24)	Dissociation (6)	Odorless. “The person does not feel the smell odorless.”	6
	Hyperarousa (2)	Sensitive to smell.”too painful to smell“	2
	Intrusion (16)	It smells like it shouldn't.“There is no offender anymore, but the smell still exists”	16
Auditiory (66)	Dissociation (10)	Inaudible	6
		Sometimes inaudible. Hearing distortion.”volume is not constant or unstable.“	4
	Hyperarousal (28)	Sensitive to life sounds. “ the person stuck with a trivial noise.”	13
		Sensitive to human voice. “Freeze to laugh.”	9
		Sensitive to words related to the trauma. “Panic when listening to the words”	1
		Panic with loud sound	5
	Intrusion (28)	Abusive voice	18
		Sound related to the trauma	4
		Word related to the trauma	6
Tactile/ Cutaneous (48)	Dissociation (14)	Painless. “No pain at wrist cut”,	11
		Other. “The person does not feel heat and cold.”	3
	Hyperarousal (17)	Sensitive to sign rerated to the trauma	3
		Sensitive to Light	1
		Sensitive to tactile	13
	Intrusion (17)	Pain	6
		Tactile related to the trauma	6
		Mouth sensation or taste related to the trauma	2
		Other	3
Gustation (23)	Dissociation (17)	Tasteless	13
		Bad taste. “The person does not feel delicious.”	2
		Abnormal taste.”Always tastes strange “	2
	Hyperarousal (1)	Vivid taste	1
	Intrusion (5)	Taste related to the trauma	5
Total (249)			2

Vision-related symptoms were the most common with 88 episodes (35.3%). Next were auditory-related symptoms in 66 episodes (26.5%) and symptoms related tactile and cutaneous symptoms in 48 episodes (19.3%). Symptoms related to olfaction were 24 episodes (9.6%), and those related to gustation were 23 episodes (9.2%).

Of the vision-related symptoms of PTSD patients, the most frequent were those related to intrusion, such as the abrupt and wholly unexpected recollection of images and pictures of the scene of the trauma or the perpetrator’s face, at 50 episodes (56.8% of visual symptoms). Categorizing the intrusions, there were 21 episodes of the scene of the trauma abruptly appearing as moving images (dynamic visual information) and 29 episodes of it appearing as still images (static visual information). The dynamic visual information was both short and long, but the images were accompanied by movement, such as "a clenched fist swinging down toward my face" or "a car coming toward me. Regarding still images, they could be fragments of a situation, such as “The perpetrator’s face appears abruptly without warning,” or a situation in its entirety, such as “The scene of trauma is suddenly recalled,” but they all had in common that they were repeated many times over and occurred suddenly and involuntarily. As such, they appeared to correspond to visual intrusive symptoms. Next were the dissociation symptoms regarded as loss of reality, such as “They see vaguely,” “They see as if through a film,” “She never sees color (always seeing objects in monochrome),” and “Their vision is distorted,” at 17 episodes (19.3% of visual symptoms).On the other hand, there were 15 episodes of what appeared to be hyperarousal, in which trauma-related information (e.g., black coat, men, etc.) caused startle or hypervigilant reactions. Thirteen of these episodes were accompanied by avoidance symptoms in an attempt to avoid hyperarousal.

Regarding auditory-related symptoms, there were 28 episodes (42.4% of auditory symptoms) that corresponded to the intrusion of sounds that were related to the traumatic event and may not currently be present, such as "suddenly hearing the perpetrator yelling," "suddenly hearing abusive voices," "suddenly hearing taunts," and "hearing sounds from the accident scene."

There were also 28 episodes (42.4% of auditory symptoms) that corresponded to hyperarousal as well, such as "overreacting to sounds" and "being overly startled by the slightest sound. Next, there were 10 episodes (15.2% of auditory symptoms) corresponding to dissociative symptoms, such as "sounds sounding muffled," "suddenly not being able to hear the person in front of me due to mouth-to-mouth interactions," and "almost all sounds suddenly disappear.

Regarding symptoms related to tactile and cutaneous sensation, there were about the same number of episodes for intrusions, hyperarousal, and dissociation. Tactile and cutaneous sensations perceived at the time of the traumatic event that should not be physically present now were considered intrusive. There were 17 episodes (35.4%) of sudden occurrences of things like “They feel touched although they are not touched,” “They feel the pain of being punched without being punched,” and “They experience an uncomfortable sensation of having things stuffed in their mouth.” Meanwhile, there were 17 episodes of oversensitive reactions (hyperarousal) to contact or somebody approaching them without actually touching, such as “They are startled when touched just slightly” and “They are startled if someone passes by behind them.” We also had 14 episodes corresponding to dissociation, such as “They do not feel any pain (11 episodes)” and “They do not know when it is hot or cold (three episodes).”

The most frequent olfaction-related symptoms were symptoms suspected to be olfactory intrusions, meaning the sensing of smells that should not currently exist, at 16 episodes (66.7% of olfaction symptoms), including “They smell rain (from the time of trauma),” “They smell the place where they were traumatized,” “They smell the gum chewed by the perpetrator,” “They smell the perfume of the perpetrator,” and “They smell the morgue.” Regarding olfactory intrusions, about half of the symptoms were recognized by the person as clearly connected to their trauma from the outset, while the other half were wholly mysterious to the person at first, but later (during treatment) identified as connected to the trauma. Second most frequent were episodes of “They sense no smells at all” and “They smell almost nothing, even though the food has a strong odor” in current everyday life at six episodes (25.0% of olfaction symptoms). Most of these were the cause of actual difficulties in everyday life, such as “The food was rotten, but they ate without realizing it.” At the same time, conversely, we also had two episodes (8.3%) of “Hypersensitivity to smells” in current everyday life.

The most common gustation-related symptoms were 17 episodes (7.9% of gustation symptoms) of suspected taste dissociation, such as "not tasting anything" and "tasteless (not tasting much)." Next were five episodes (2.0% of gustation symptoms) of "tasting (trauma-related; e.g., semen or blood)" even though they were not currently eating.

All 249 episodes could be classified into three categories: intrusion, overactivity, and dissociation. Therefore, the three sensory organs(vision, auditory, and tactile/cutaneous sensation), excluding gustatory and olfactory, which had fewer than 5 cells, were analyzed using the chi-square test to compare the occurrence of the three symptoms (intrusion, hyperactivity, and dissociation), and significant differences were found (χ2 (4) = 15.24, V = 0.194, p < .004). The residual test showed that intrusion was significantly more frequent in vision(p < .05), whereas hyperarousal was less frequent (p < .01). That is, 52.6% of the intrusive symptoms occurred in vision, and the frequency of unintentional intrusions of trauma-related visual images in daily life was significantly higher than that of sound or cutaneous sensory and experiential intrusions. In auditory, on the other hand, hyperarousal was significantly more frequent. 46.7% of hyperarousal symptoms occurred in auditory, with significantly more hypersensitive reactions to the slightest sound in current daily life (p < .01).

Next, it was examined whether there were differences in PTSD symptoms and in the five sensory organs in which symptoms appeared, depending on whether the traumatic experience was single or multiple (experiencing one or more types of trauma, such as sexual assault, child abuse, violence/domestic violence, natural disasters, car or other accidents, or witnessing a suicide).The results showed that there were no differences in the sensory organs in which symptoms occurred (p = 0.778). However, there were differences with respect to symptoms (χ2(2) = 21.50,V = 0.29, p < .0001). When there was only one type of traumatic experience, intrusion was significantly more common (75.0%) and dissociation was significantly less common (18.8%) (p < .01). On the other hand, when there were two or more types of traumatic experiences, dissociation was significantly more common at 46.1% and "intrusion" was significantly less common at 32.6% (p < .01).

Categorizing Types of Traumatic Experiences and Symptoms

To investigate whether the sensory symptoms of PTSD differ according to the traumatic experience, the quantification method of the third type was used to classify the symptoms. The quantification method of the third type (Hayashi, 1993) is a type of correspondent analysis, but they differ only in the format of the analyzed data. In other words, cross-tabulations are applied in correspondence analysis, whereas response data are applied in the third type of quantification method. Classification was attempted using the following variables: PTSD symptoms (intrusion, hyperarousal, dissociation), sensory organs showing symptoms (vision, auditory, olfaction, tactile and cutaneous sensation, and gustation), and type of traumatic experience (multiple traumas [two or more types of trauma], single trauma [sexual assault, child abuse, violence/domestic violence, natural disaster, accident]).Having implemented the quantification method, a 26.78% cumulative contribution ratio was found for the axes. Each axis had a unique value with axis 1 at .53 and axis 2 at .45. As axis 1 had a distribution of “hyperarousal” (0.87) and “intrusion” (0.61) in a positive direction, and “dissociation” (-1.79) in a negative direction, it was interpreted as an axis for symptom activity. By contrast, as axis 2 had a distribution of “child abuse” (0.85), “violence/domestic violence (0.55), and “multiple traumas” (0.45) in the positive direction, and “sexual assault” (-0.63), “natural disaster” (-0.64), and “accident” (-1.63)” in the negative direction, it was interpreted as an axis for the persistence and repeatability of the traumatic event. The category and samples scores from the quantification method are shown in Table 2. Axis 1 was used as the horizontal axis, and axis 2 as the vertical axis to create a two-dimensional scatter plot using the category scores for 14 items (Fig. 1). A cluster analysis of the category scores was conducted using Ward’s method to derive three interpretable clusters that were represented in the scatterplot. Cluster 1 is a group formed by “violence/domestic violence” and” child abuse,” together with “auditory,” “tactile and cutaneous sensation,” and “hyperarousal.” Cluster 2 is made up of “natural disaster,” “accident,” and “sexual assault,” together with “vision,” “olfaction,” and “intrusion.” Cluster 3 is made up of “multiple traumas” together with “gustation” and “dissociation.” There was a separation between numbers of traumas (whether the person has experienced one or multiple types of trauma) and the persistence and repeatability of the traumatic event in terms of what symptoms manifest and in which sensory organs they manifest [See Table 2 & Fig. 1].

Table 2.

The category score from the quantification method

Category	Axis I	Category	Axis II
Violence/DV	1.76	Hyperarousal	1.63
Hyperarousal	0.87	Audition	1.29
Disaster	0.86	Tactile/cutaneous	0.92
Audition	0.76	Child abuse	0.85
Child abuse	0.76	Violence/DV	0.55
Accident	0.70	Multiple	0.45
Intrusion	0.61	Dissociation	0.14
Sexual assault	0.33	Gustation	-0.10
Vision	0.20	Sexual assault	-0.63
Olfaction	0.06	Disaster	-0.64
Tactile/cutaneous	-0.17	Vision	-0.81
Multiple	-1.15	Intrusion	-0.95
Dissociation	-1.79	Accident	-1.63
Gustation	-2.69	Olfaction	-2.32

Fig. 1.

The classification of sense symptoms

Discussion

The results of this study showed that of 249 symptoms in the five sensory organs, symptoms in vision were the most frequent at 88 (35.3%). This was followed by auditory at 66 (26.5%), tactile and cutaneous sensation at 48 (19.3%), olfaction at 24 (9.6%), and gustation at 23 (9.2%). Ehlers et al. (2002) examined intrusive symptoms only in the sensory organs, and the results of this study, which also included other PTSD symptoms such as hyperarousal and dissociation, also showed that visual symptoms manifested most frequently. Vision is said to be the sensory organ that takes in the largest volume of information, as much as 80% of the total (Zimmermann, 1976). This is possibly why vision is the most susceptible to damage or impairment.

The ways in which the symptoms manifest in the different sensory organs were compared and it was found that intrusive symptoms were significantly frequent in vision. This result is in agreement with previous studies (Ehlers et al., 2002; Hackmann et al., 2004).

The results of the correspondent analysis suggested that intrusive symptoms were more likely to occur in olfaction. The present results show that 66.7% of the symptoms occurring in olfaction were intrusive symptoms (16 out of 24 episodes). Although studies have shown a strong association between olfaction and trauma memories (Cortesea et al., 2018; Daniels & Vermetten, 2016; Dileo et al., 2008; Vasterling et al., 2000), and few studies have investigated intrusive symptoms in the sense of smell. Future research on trauma symptoms related to olfaction, especially intrusive symptoms, needs to be conducted with larger sample sizes.

The results of the correspondence analysis suggest that hyperarousal symptoms may be more likely to occur in the auditory. This result is consistent with previous findings that many PTSD patients have auditory hyperarousal symptoms.

Menning et al.(2008) suggested that there was a reduction in pre-attentive auditory sensory memory in PTSD because of specific symptom variables, such as hyperarousal, sleeplessness, impaired concentration, and a general enhanced excitation of the nervous system. Zukerman et al. (2018) suggested that trauma exposure may lead to hyperarousal at early processing levels, even in response to neutral novel auditory stimuli. In clinical situations, it is often observed that abused children are terribly alarmed, even by a trifling sound. A further study of auditory hyperarousal symptoms in PTSD should be conducted.

On the other hand, for gustatory symptoms, the results of the correspondent analysis showed that gustatory and dissociative symptoms formed one group.73.9% (17 of 23 episodes) of the symptoms occurring in gustatory sensation were disassociations.

Few studies have examined gustation symptoms in PTSD. However, there is much research on the strong association between eating disorders and PTSD (Tagay et al., 2014; Brewerton & Costin, 2007; Arditte Hall et al., 2017). Eating behavior is one of the major factors affecting physical and mental health and quality of life, and further investigation is needed to understand the impact of dissociation on eating disorders and taste disorders in individuals with PTSD.

Furthermore, symptoms were compared in cases of several or overlapping traumas and it was found that while intrusion is most frequent for singular trauma, dissociation is most frequent for multiple traumas. When breaking down multiple traumas in this study, 89 out of 249 (35.7%) were symptoms manifested in persons who have suffered multiple traumas. All overlapping traumas were combinations of human traumas (child abuse, sexual assault, violence/domestic violence), with 77 out of 89 symptoms found in persons who had suffered sexual assault. As such, the overlapping traumas in this study can be interpreted as persons who have suffered human traumas (especially sexual assault). Previous studies have shown that dissociation symptoms are common in cases of sexual assault and that dissociation symptoms are frequently found in cases of complex PTSD (Putnam, 1997; Herman, 1992; Nijenhuis et al., 1998; Nijenhuis, 2004), so the results of this study also support this view.

An attempt was also made to categorize types of traumatic experiences, types of PTSD symptoms, and the sensory organs where symptoms manifest, which suggested the possibility that psychological traumas manifest mainly in three patterns. Each category includes types of psychological trauma events. Natural disasters, accidents, and sexual assault made up one group, together with visual and olfactory intrusion. Natural disasters, traffic accidents, witnessing suicides, and sexual assaults are events that occur unexpectedly and suddenly in daily life. Therefore, it is inferred that these events, along with shocking visual images, smells, etc., are accumulated unorganized by the individuals involved and subsequently cause intrusive symptoms in the form of flashbacks. As specific examples, the data in this study showed shocking visual images and smells of natural disasters, accidents, and sexual assaults (semen, blood, decomposing bodies in the morgue, and burning rubber during traffic accidents).

On the other hand, child abuse, and domestic violence/violence were distributed near hyperarousal in auditory and tactile sensation on the scatter plot. Child abuse and violence/domestic violence are all traumas mediated by repeated intentional human violence and normally involve blows and other forms of physical contact, which likely affected this result. Moreover, violence includes not only physical contact, but also verbal violence, that is, repeated abusive and disparaging language. It is speculated that survivors of child abuse by other people are hypersensitive to sounds, the presence of others, and physical contact because they try to quickly sense when a perpetrator is approaching.

Moreover, multiple traumas (two or more kinds of traumas) made up one group with gustation and dissociation. According to Nin et al. (2017), 17.6% of dysgeusia symptoms are psychogenic, so that symptoms such as reduced taste, loss of taste, dissociative gustatory disorder, and spontaneous abnormal taste may have psychological causes. Sakaguchi et al. (2013) also suggests that gustatory disorders may be related to mental disease. It has also been reported that dissociation symptoms that manifest physically are common in cases of dissociation from physical contact, such as sexual assault and physical abuse that injures the body (Nijenhuis, 2004; Nijenhuis et al., 1998). The mouth is the site of first contact between mother and child, and it is possible that gustatory dissociation may occur mainly in cases of severe and repeated physical and sexual trauma since early childhood, but this merely remains a conjecture by the authors. More research is needed on the possibility that PTSD symptoms may cause taste insensitivity and dissociation. However, as mentioned above, there are also research results that demonstrate a strong link with eating disorders (Tagay et al., 2014; Brewerton & Costin, 2007; Arditte Hall et al., 2017), so it is possible that gustatory issues also arise against a background of eating-related issues.

The above discussion suggests the possibility that PTSD symptoms and the sensory organs in which they manifest may differ depending on the type of traumatic experience. Further and more detailed elucidation of this may offer useful insights for involving the senses in therapy. It can also provide information on considerations for PTSD patients in court and other legal situations.

Application to Clinical Support

Although often lumped together as PTSD, the main symptoms and psychological damage differ depending on the traumatic experience, and therefore, the treatment needed is also different. Recently, an increasing number of studies have examined the differences in symptoms among traumatic experiences using network analysis (Benferet al., 2018; Stefanovic et al., 2022). In the future, the treatment of PTSD will need to be increasingly refined to incorporate findings by traumatic experience and symptoms suffered, as well as by the demographics of the individuals involved. The findings of this study that the primary symptoms and the sensory organs in which they occur differ depending on the traumatic experience may provide some suggestions for PTSD therapists to keep in mind in clinical support settings. If these findings were accumulated and if therapists were primed to pay attention to their clients' sensory symptoms before meeting them, the accuracy of their perceptions could be of higher quality in the future, potentially improving the quality of treatment.

Limitations and Prospects

This survey involved the collection of data from interviews, not with PTSD patients but with their therapists, to collect more wide-ranging data and avoid placing a burden on the patients. As such, the study was limited in various ways, since it was not possible to include detailed data about the traumas because of professional ethics and confidentiality, and since the study had to rely heavily on the therapists’ memories.

This survey took the form of asking supporters to recount their support experiences, and supporters gathered information about the traumatic experiences of PTSD sufferers through the PTSD sufferers' recollections. One problem with this study is that it cannot dispel the possibility of a retrospective bias (Shachar & Eckstein, 2007) that there is a gap between the actual experience and the retrospective, which is doubly likely to occur.

Conclusion

Treatment of PTSD has increasingly focused on sensory symptoms. In this study, we investigated the symptoms exhibited in the sensory organs of persons with PTSD and whether there were differences based on the type of traumatic experience. 249 PTSD symptoms exhibited in the sensory organs obtained from a survey of clinical psychologists involved in PTSD treatment were analyzed. Results showed that sensory organ symptoms were classified into three categories according to the type of symptom and the type of trauma. It was suggested that child abuse and violence may produce hyperarousal symptoms in auditory and tactile senses, natural disasters, accidents, and sexual assault may produce intrusive symptoms in visual and olfactory senses, and multiple traumas may cause dissociative symptoms in taste. Survivors of child abuse and violence are presumed to be hypersensitive to sounds, the presence of others, and physical contact, as they attempt to quickly detect the approach of the perpetrator. Natural disasters, accidents, and sexual assaults are events that have a strong odor and visual impact and may be easily relived in the form of shocking images and smells called flashbacks. Dissociative symptoms were associated with complex trauma and taste. The mouth is the site of first contact between mother and child, and it is possible that gustatory dissociation may occur when the mother has been repeatedly exposed to severe trauma, mainly from early childhood.

Declarations

Conflicts of Interest

We have no known conflicts of interest, or competing interests to disclose.