Differential odor sensitivity in PTSD: Implications for treatment and future research

Abstract

Background Given that odors enhance the retrieval of autobiographical memories, induce physiological arousal, and trigger trauma-related flashbacks, it is reasonable to hypothesize that odors play a significant role in the pathophysiology of posttraumatic stress disorder (PTSD). For these reasons, this preliminary study sought to examine self-reported, odor-elicited distress in PTSD. Methods Combat veterans with (N=30) and without (N=22) PTSD and healthy controls (HC: N=21), completed an olfactory questionnaire that provided information on the hedonic valence of odors as well as their ability to elicit distress or relaxation. Results Two main findings were revealed: Compared to HC, CV+PTSD, but not CV-PTSD, reported a higher prevalence of distress to a limited number of select odors that included fuel (p=.004), blood (p=.02), gunpowder (p=.03), and burning hair (p=.02). In contrast to this increased sensitivity, a blunting effect was reported by both groups of veterans compared to HC that revealed lower rates of distress and relaxation in response to negative hedonic odors (p=.03) and positive hedonic odors (p<.001), respectively. Limitations The study is limited by its use of retrospective survey methods, whereas future investigations would benefit from laboratory measures taken prior, during, and after deployment. Conclusion The present findings suggest a complex role of olfaction in the biological functions of threat detection. Several theoretical models are discussed. One possible explanation for increased sensitivity to select odors with decreased sensitivity to other odors is the co-occurrence of attentional bias toward threat odors with selective ignoring of distractor odors. Working together, these processes may optimize survival.

Burning odor-elicited anxiety in OEF/OIF combat veterans: Inverse relationship to gray matter volume in olfactory cortex

“…Odor intensity (i.e., “the odor was strong”) and negative valence (i.e., “the odor was unpleasant”), as well as baseline and odor-elicited ratings along the 3 symptom clusters of PTSD including re-experiencing (i.e., “the odor triggered memories of my trauma”), avoidance and numbing (i.e., “the odor made me feel numb”), and hyperarousal (i.e., “the odor made me feel anxious”) were acquired on 100mm visual analog scales (VAS) with anchor points of “not at all” to “extremely”. The odor cues (ScentAir ™ , Charlotte, NC) were selected based upon survey data collected in our laboratory (Cortese, Leslie, 2015) and included burning rubber (BR), a trauma-related “burning” odor cue; lavender (LAV), a relatively pleasant non-trauma-related control odor cue; cigarette smoke (SMK), a “burning” odor that was generally not identified as an odor related to combat experiences in our sample; and propylene glycol (PG) which served as the odorless control as well as the base oil for preparing the other odor cues. Similar to previously published methods, the odor cues were prepared and pilot tested for an average intensity rating of 50mm (Khan et al, 2007).…”

“…Other studies designed to assess clinical olfactory function in PTSD have been inconsistent (Croy et al, 2010, Dileo et al, 2008, Vasterling et al, 2000, Vasterling et al, 2003). However, recent preliminary data from our laboratory suggest that trauma-exposed combat veterans with and without PTSD may have a decreased ability to detect odors (Cortese et al, 2014), in addition to a self-reported reduction in general odor sensitivity (Cortese et al, 2015). It remains to be seen the degree to which this reduced sensitivity to odor is the result of generalized hyposmia, damage to the olfactory mucosa/receptors, perceptual difficulties mediated by cortical damage, or some combination of these factors.…”

Subjective Health Complaints Among Workers in the Aftermath of an Oil Tank Explosion

“…A study among residents exposed to malodorous emissions from a biofuel facility suggested that neither annoyance nor health complaints were mediated by the malodourous pollution itself, but rather by perceived air pollution and health risk perception [66] (Table 5). Furthermore, olfaction has a complex role in threat recognition [77] (Table 6). …”

“…After conditioning the foul odour might by itself evoke a similar response through a conditioned reflex (Figure 23). Previous studies have suggested this kind of mechanism [72,75,77,101,102]. One experimental study put forward that aversive learning through conditioning increases the participant's sensitivity to the specific odour [101], and a single study has even suggested that perceived smells play a significant role in the pathophysiology of post-traumatic stress disorder (PTSD) [77].…”

“…However, one experimental study suggested that fear conditioned to odours extinguished slowly [72], and in soldiers who develop PTSD even an inability to extinguish the conditioned fear response has been shown [77]. Odour is not the only factor that could be of importance for the development and persistence of psychological health complaints.…”