Neuropeptide S (NPS) is a recently discovered G protein-coupled receptor ligand that modulates fear-like behaviors in rodents. A frequent A>T single-nucleotide polymorphism in the human NPS receptor gene NPSR1 confers a 10-fold higher efficacy of NPS signaling in vitro and has been linked with panic disorder (PD). We here report data from a classical fear-conditioning paradigm in healthy normal volunteers, in which carriers of the NPSR1 T allele evaluated their fear reactions to conditioned stimuli (CSs) as more pronounced than AA homozygous participants, although they did not show elevated peripheral-physiological conditioned responses (skin conductance responses—SCRs). T carriers also exhibited stronger CS-evoked brain activity in the rostral dorsomedial prefrontal cortex (dmPFC), an area that supports the explicit, conscious appraisal of threat stimuli. By contrast, more caudally situated mid-dmPFC, which has previously been associated with the generation of SCRs, showed no elevated response. Moreover, rostral dmPFC activation was correlated with participants’ fear evaluations, further strengthening the link of this activation to increased individual fear appraisal. Our data suggest a genetic and neuroanatomical substrate for catastrophizing overinterpretations of fear reactions and provide a mechanistic explanation for the association between the NPSR1 T allele and PD.
Neuropeptide S (NPS) binds to a G protein-coupled receptor to induce a rise in intracellular calcium and cAMP levels.1, 2 Recent evidence from rodent models indicates that the NPS system is critically involved in the regulation of unconditioned and conditioned fear behaviors.1, 3, 4, 5, 6, 7 In humans, the locus for the NPS receptor gene NPSR1 maps to a chromosomal region that has reproducibly been linked to panic disorder (PD), with those markers creating the highest logarithm of the odds (LOD) scores lying in close vicinity to the NPSR1 locus.8, 9, 10 NPSR1 contains a frequent A>T polymorphism (rs324981) that codes for an Asn/Ile change at position 107.11 The Ile107 variant encoded by the T allele massively enhances the potency of NPS in cell-based assays.2 First data indicate a link between this molecular alteration and human fear behavior in that the NPSR1 A allele has been shown to be under-represented in a sample of Japanese PD patients.12 These results have recently been confirmed and extended in two large German samples (Domschke et al., in revision at Mol Psychiatry).
In the psychological domain, two theoretical approaches have been dominant in trying to explain the development and maintenance of PD. Learning theoretical accounts see classical conditioning as a key process. For instance, one may learn to fear interoceptive or exteroceptive stimuli (conditioned stimuli, CSs) co-occurring with an occasional panic attack (unconditioned stimulus, UCS), with the result that these otherwise neutral stimuli come to trigger attacks (conditioned responses—CRs) in the future.13, 14 A more recent variant of this theory holds that vulnerable individuals also generalize their conditioned fear responses to stimuli resembling those co-occurring with panic.15, 16 Both mechanisms lead to a proliferation of panic-evoking CSs. Cognitive theories, in contrast, attribute a central role to conscious thought processes that lead to a catastrophizing misinterpretation of interoceptive or exteroceptive stimuli as signaling threat.17, 18, 19 For example, in an arousing situation, symptoms such as shortness of breath, a feeling of nervousness or difficulties to concentrate may be appraised as indicating impending harm, this may further amplify these symptoms and thus initiate a vicious cycle, which finally results in the elicitation of a panic attack.
On the basis of the findings that PD has a heritability of 48% (Hettema et al.20) and above report of a link between the NPSR1 T allele and PD, we wondered whether the associative learning of CS–UCS contingencies and/or the subjective appraisal of CS-associated CRs is affected by NPSR1 genotype. In our sample of 66 male healthy normal volunteers (see below, Supplementary Materials and Methods), only few participants were homozygous for the T allele. We thus compared homozygous A carriers (‘AA’) with participants carrying one or two T alleles (AT or TT, ‘T+’) on a simple uninstructed fear conditioning, extinction and reacquisition task. In the acquisition phase (‘Acq’), participants repeatedly saw two geometric symbols (a circle, a triangle), one of which (CS+) was paired in 80% of cases with a painful electric stimulus (UCS). The other symbol served as a control stimulus (CS−) for non-associative effects and was never paired with the UCS. In the extinction phase (‘Ext’), both stimuli were again presented multiple times, but in the absence of the UCS. The subsequent reacquisition phase (‘RAcq’) was identical to the acquisition phase.
Conditioned emotional responding is multifaceted and normally involves an orchestrated reaction of autonomic, endocrine, motor, cognitive and subjective-experiential (feeling) systems. During the task, we acquired CS-evoked skin conductance responses (SCRs) as an index of the sympathetic arousal accompanying conditioned fear. As the measure is implicit, it is not confounded by subjective factors. We also intermittently asked participants to give explicit ratings of their CS-evoked stress/fear/tension. Systematic (for example, genetically determined) inter-individual variation in the subjective evaluation of emotional responses can arise because (a) the consciously accessible components of the emotional response (such as noticeable bodily reactions, or feelings) are systematically different between individuals, (b) individuals with a tendency for socially desirable responding do not accurately report the full extent of their reactions,21 or (c) individuals subjectively appraise their responses differently, that is, under- or overestimate them in a systematic manner, although they may not necessarily differ at the objectively measurable physiological level. This allowed us to hypothesize that, if NPSR1 genotype affects associative learning, there should be an AA vs T+ group difference in discriminative conditioning. More specifically, if the T allele confers exaggerated fear conditioning,13, 14 T carriers should show higher CS+>CS− difference scores than AA homozygotes; however, if the T allele confers overgeneralization,15, 16 we should expect lower difference scores. The latter would be because T-allele carriers generalize their conditioned responding to stimuli resembling the predictive CS (CS+), that is here, to the CS−. In either case, such a result would suggest a potential mechanistic link between NPSR1 genotype and PD on the basis of NPSR1's impact on fear conditioning. Differences should be observed in SCRs and ideally also in fear ratings. If, in contrast, NPSR1 genotype affects subjective appraisal only, then T carriers should show higher fear ratings than AA homozygotes in the absence of comparable differences in SCRs. Such a finding would suggest that the NPSR1 T allele confers a higher risk for PD because it promotes catastrophizing-like processes.17, 18, 19
We further measured task-induced brain activation changes using concurrent functional magnetic resonance imaging (fMRI), to test two associated anatomical hypotheses. The dorsal anterior cingulate cortex (dACC) and adjacent dorsomedial prefrontal cortex (dmPFC) are increasingly recognized as important, if not central, parts of the fear circuitry. The mid-dACC/dmPFC is the only brain region consistently activated across classical discriminative fear-conditioning studies (see Mechias et al.22 for meta-analysis). In line with animal research, the area has been associated with the generation of autonomic CRs, in particular SCRs.23, 24, 25 It is also the only area that could be shown to be common to both classical conditioning tasks (in which learning occurs by experience) and instructed fear paradigms (in which learning occurs before CS presentation through verbal instruction)—two paradigms that mainly share a CR generation component.22 We thus predicted that, if NPSR1 genotype groups indeed show different discriminative conditioning in their SCRs, this should be paralleled by differential CS-evoked responses in the mid-dACC/dmPFC (higher CS+>CS− responses in T carriers compared with AA homozygotes in the case of exaggerated fear conditioning, lower CS+>CS− responses in T carriers compared with AA homozygotes in the case of overgeneralization). Such a result would further strengthen the idea of a mechanistic link between NPSR1 genotype and PD by modified associative learning.
A more rostral part of the dACC/dmPFC has been shown to be involved in the conscious appraisal of threat, but not in the generation of subjective or sympathetic-conditioned responses.26 This conclusion has recently been supported by a meta-analysis of studies investigating the explicit evaluation of emotional stimuli or reactions more generally,27 and by a meta-analysis of instructed fear studies, where conscious appraisal is a dominant component.22 Further evidence indicates that the area is most likely also not implicated in the associative learning of CS–UCS contingencies.28 Therefore, if NPSR1 genotype groups indeed show differences in fear ratings, this should be paralleled by differential CS-evoked responses in the rostral dACC/dmPFC (higher CS responses in T carriers than in AA homozygotes). This would support an appraisal-theoretic account of the NPSR1–PD association.
Materials and methods
The study was conducted in a sample of (n=66) healthy male right-handed participants, originally preselected for polymorphisms in the dopamine system (in the dopamine transporter (DAT1) and catechol-o-methyltransferase (COMT) genes). The preselection was carried out to obtain six equally sized groups (factors DAT1 with levels 9repeat carriers or 10repeat homozygotes and COMT with levels Val/Val, Val/Met or Met/Met) and served to assess possible effects of these candidate polymorphisms on extinction learning. The results of this analysis will be reported elsewhere. Among these participants, 28 individuals were homozygous for the NPSR1 A allele (‘AA’, mean age 27.8 years, age range 23–40 years) and 38 carried one or two NPSR1 T alleles (‘T+’; 25 AT, 13 TT; mean age 28 years, age range 19–42 years). Further, we genotyped subjects for two polymorphisms that have previously been shown to affect fear conditioning (in the brain-derived neurotrophic factor (BDNF) and serotonin transporter (SLC6A4) genes29, 30). χ2-tests indicated that only BDNF allele frequencies were unequally distributed between NPSR1 genotype groups (see also Supplementary Table S1). We thus controlled for potential BDNF, and BDNF by NPSR1 interaction, effects by treating these as covariates in all analyses reported below. Introducing DAT1, COMT and SLC6A4 genotypes and the corresponding interactions as further covariates yielded similar results, and all effects reported as significant below were also significant in these additional analyses (data not shown). Screening and genotyping methods are described in the Supplementary Methods and Supplementary Figure 1. Signed informed consent was obtained from all participants, and all procedures were approved by the ethics committee of the Medical Board of the State of Hamburg and were in accordance with the Declaration of Helsinki and relevant national and regional regulations.
CSs were a white circle and a white triangle presented on a black background. The white circle was the CS+ in 12 AA homozygotes and in 19 T carriers, the white triangle was the CS+ in 16 AA homozygotes and in 19 T carriers. UCSs consisted of brief triple painful electric stimuli to the right hand. Stimuli were applied using a Digitimer DS7A electrical stimulator (Digitimer, Welwyn Garden City, UK) delivering 2 ms square-wave pulses of 0.01–100 mA through a surface electrode with platinum pin (Clyde's Polo Kit Supplies, Bexley, UK). Stimulation parameters were individually adjusted before the experiment to achieve maximum tolerable pain as described earlier.31
Participants had to perform a speeded decision task for which they signaled whether they saw the circle or the triangle by pressing the left and right buttons, respectively, on a keypad with their right hand's index or middle finger, respectively, as soon as they saw the symbol. They knew that they would receive shocks several times during the experiment, but no indication of contingencies and no information about conditioning or extinction was provided beforehand. Participants were first habituated to the CSs, to the task and to the scanner noise by presenting each CS four times before the actual experiment. The experiment consisted of an acquisition, an extinction and a reacquisition phase, which followed immediately upon each other with no break or change in context. In each phase, each CS was presented 18 times for 5 s in a randomized order, with the limitation that no CS type could occur more than twice in a row and that the number of CS+'s and CS−'s had to be equal in every block of 12 trials. The duration of the inter-trial interval was jittered between 9 and 14 s, with an average of 11.5 s. During the acquisition and reacquisition phases, 15 CSs coterminated with a UCS. At the onset of the experiment and every 12 trials thereafter, participants rated how much stress/fear/tension the symbols had caused them by moving a red dot to the corresponding position on a visual analog scale that ranged from 1 (no stress at all) to 100 (very much stress), with the help of the keypad.
Skin conductance and functional magnetic resonance imaging data acquisition followed standard procedures (see Supplementary Methods).
Significance of behavioral effects was assessed using analysis of variance (ANOVA) within the general linear model framework of SPSS 17.0 (SPSS, Chicago, IL, USA). The significance threshold was set at P=0.05.
Skin conductance data were down-sampled to 100 Hz and visually inspected for artifacts. Artifacts related to electrical stimulation were removed and time courses were interpolated. Three participants did not show any apparent SCR to the UCS and were excluded from further skin conductance analysis. In eight participants, data were not acquired or lost due to technical problems. The remaining sample size for SCR analysis was n=22 in the AA and n=33 in the T+ group. A CS-evoked SCR was defined as the maximum skin conductance in a time window of 5 s after CS onset minus skin conductance at the time of CS onset. UCS-evoked SCRs were scored analogously over 10 s.
Fear rating data were not acquired or lost in four participants due to technical problems. The remaining sample size for analysis of ratings was n=26 in the AA and n=36 in the T+ group. Because rating data loss occurred exclusively in participants, which had useful SCR data, there was an overlap of n=21 participants in the AA and n=30 participants in the T+ group, in which both types of data could be analyzed.
Reaction times and accuracy
Decision task responses were not acquired or lost due to technical problems in seven participants. The remaining sample size for the analysis of task performance was n=26 in the AA and n=33 in the T+ groups. There were no significant effects of stimulus, time or genotype on reaction times. Accuracy was high (only 22 omissions and 21 wrong responses in all participants across the entire experiment) and was not further analyzed.
Imaging data were preprocessed and analyzed using standard procedures (see Supplementary Methods). The data from all 66 participants could be used for the analysis.
NPSR1 genotype groups did not differ in their trait anxiety, trait negative or positive affect, or depression scores, and also had a similar tendency for socially desirable responding (Supplementary Table S1). To assess potential genotype effects on arousal and wakefulness,1 we analyzed relevant subitems from the positive and negative affect schedule. None showed significant group differences (Supplementary Table S1). UCS reactivity was similar between groups: there were no significant differences in the electrical stimulus current level at pain threshold and at the tolerable pain maximum (which was used as UCS), and UCS-SCRs did not differ significantly between groups (Supplementary Table S1). Finally, there were no significant group differences in CS+ or CS− associated fear ratings after habituation (that is, at the onset of the acquisition phase; see Supplementary Table S1).
Given absence of measurable differences in basic emotional personality traits, UCS reactivity and baseline response appraisal, which all might impact on fear-learning propensity, we questioned our SCR and fear rating data from the three experimental phases (Figure 1; see Supplementary Table S2 for results in tabular form) for NPSR1 effects. We used separate ANOVAs for the three phases, each with within-subject factors stimulus (CS+, CS−) and time (SCR data averaged into three time bins of six trials each per phase; three ratings per phase) and a between-subject factor Genotype (AA, T+). SCR values were normalized to the first trial of a given phase. Rating values were normalized to the last rating of the preceding phase (that is, to the post-habituation rating for Acq, the last Acq rating for Ext, and the last Ext rating for RAcq).
SCRs in the acquisition phase showed significant stimulus (F(1, 50)=29.44, P<0.001) and time (F(1, 50)=7.34, P=0.009) effects and a significant stimulus by time interaction (F(1, 50)=21.19, P<0.001) attesting for successful conditioning that built up over the course of acquisition. There were no significant genotype effects (P=0.553) or interactions of genotype with other factors (P>0.362). Fear ratings in the acquisition phase also showed stimulus (F(1, 58)=202.02, P<0.001) and time (F(1, 58)=4.43, P=0.04) effects and a stimulus by time interaction (F(1, 58)=12.03, P=0.001). In addition, there was a significant effect of genotype (F(1, 58)=8.98, P=0.004) that did, however, not interact with the other factors (P>0.13). To better characterize how NPSR1 genotype influenced fear ratings, we conducted three separate post hoc ANOVAs on CS+ ratings, CS− ratings, and CS+>CS− difference scores averaged across the phase. These showed that, as suggested by Figure 1, T carriers reported significantly more fear of both the CS+ (F(1, 59)=5.61, P=0.021) and the CS− (F(1, 59)=6.68, P=0.012), but showed similar discriminative conditioning (CS+>CS−: F(1, 59)=1.17, P=0.28). The absence of detectable NPSR1 effects on both physiological and subjective measures of CS+ vs CS− discrimination indicates that NPSR1 genotype does not influence associative learning. By contrast, T-allele carriers evaluate their CS-evoked emotional responses as more pronounced.
In the extinction phase, SCRs showed a stimulus effect (F(1, 50)=15.05, P<0.001) and a stimulus by time interaction (F(1, 50)=14.84, P<0.001) in line with developing CR inhibition. All other effects were nonsignificant (P>0.159). Fear ratings showed stimulus (F(1, 58)=202.02, P<0.001) and time (F(1, 58)=23.18, P<0.001) effects and a stimulus by time interaction (F(1, 58)=21.16, P=0.001). The significant genotype effect (F(1, 58)=6.57, P=0.013) was due to comparatively higher CS+ ratings in T carriers apparently resulting from previous conditioning (post hoc ANOVA on average CS+ ratings: F(1, 59)=3.73, P=0.058). CS+ ratings in this group not only started from a higher level but also showed a steeper decline (difference between last Acq and last Ext CS+ rating; post hoc ANOVA: F(1, 59)=4.03, P=0.049), which resulted in similar ratings as in AA homozygotes at the end of extinction. Thus, both groups did equally well in extinguishing their fear responses.
In the reacquisition phase, SCRs showed a strong stimulus effect (F(1, 50)=17.78, P<0.001), but only a trend-like time effect (F(1, 50)=3.26, P=0.077) and no stimulus by time interaction (P=0.661), suggesting that reacquisition of conditioned SCRs occurred very rapidly. All other effects were nonsignificant (P>0.172). Reacquisition in fear ratings occurred less rapidly (stimulus: F(1, 58)=202.02, P<0.001; time: F(1, 58)=2.69, P=0.091; stimulus by time: F(1, 58)=12.81, P=0.001) but there was only a trend-like genotype effect (F(1, 58)=3.31, P=0.074), potentially linked to differences in CS+ ratings (post hoc ANOVA: F(1, 59)=3.24, P=0.077). Fear reacquisition thus seems to be a less sensitive scenario for detecting NPSR1 genotype effects on fear ratings compared with acquisition.
We also calculated analyses in which we split participants into three genotype groups (AA, AT, TT). Findings suggest a dominant T-allele effect, a conclusion that is, however, limited by the small number of TT carriers in our sample (see Supplementary Table S3). Thus, further studies will be needed to clarify whether the T allele has a dominant influence on fear evaluations.
Taken together, our behavioral data suggest a genuine influence of NPSR1 on how participants consciously appraise their emotional reactions to stimuli that signal potential threat. They show no evidence for a role of NPSR1 in associative fear learning. Because the conscious appraisal effect was most pronounced during the acquistion phase, we focussed our fMRI analysis on this part of the experiment. We expected stronger rostral, but not mid, dACC/dmPFC activation to CSs in T carriers relative to AA homozygotes (see Introduction section). A cluster in the right rostral dACC/dmPFC region-of-interest (see Supplementary Methods for definition) showed the predicted group difference in response to CS+'s (Figures 2a,b). Surprisingly, CS− responses did not show the same effect despite of a group difference in CS− ratings (see above). A possible explanation is that neural CS− responses were generally so low and hardly above noise that any potential group differences were masked by noise. Nevertheless, the rostral dACC/dmPFC CS+ response was significantly correlated across participants with average CS+ ratings (R=0.317, P=0.011; Figure 2c) during acquisition, including when controlling for CS+ SCRs (R=0.312, P=0.026). This substantiates a relation between conscious threat appraisal and activity in the rostral dACC/dmPFC. There were no corresponding activation group differences in mid-dACC/dmPFC (P<0.001 uncorrected).
In line with an absence of NPSR1 effects on behavioral indices of associative learning, there were no detectable activation group differences across the entire imaging volume for the CS+>CS− difference contrast (P<0.01 uncorrected). Results from an exploratory whole-brain level analysis are reported in Supplementary Table S4. The imaging data thus further support the idea that NPSR1 T carriers appraise their fear reactions in a more negative manner.
Our data provide evidence that individuals who carry the NPSR1 T allele over-interpret their conditioned fear reactions compared with non-T carriers. Participants with a T+ genotype rated the stress/fear/tension evoked by CSs during the acquisition phase as more pronounced than AA homozygotes. Because bodily reactivity as indexed by SCRs was not different between groups and because both groups showed a similar propensity to respond in a socially desirable manner, this group difference in subjective fear ratings most likely reflects a general negative appraisal tendency in T carriers. Furthermore, enhanced fear ratings were associated with enhanced responding of a dorsal ACC/mPFC area previously associated with the conscious appraisal of threatening stimuli or situations. By contrast to this convergent set of findings, we observed no indication in either peripheral-physiological, subjective or neural response measures for an effect of NPSR1 genotype on CS+ vs CS− discrimination, strongly suggesting that NPSR1 genotype does not influence associative learning in our paradigm.
Because the T allele has been linked with PD,12 our results are of theoretical interest for the understanding of PD etiology. They allow for hypothesizing that T-allele carriers are at increased risk to develop PD because of an innate tendency to mis-interpret their affective responses to arousing or aversive stimuli in a catastrophizing manner. This explanation would be in line with prominent cognitive theories of panic.17, 18, 19 It is important to note that our data give the first strong hint as to where in the brain catastrophizing might occur (rostral dACC/dmPFC) and which neurotransmitter systems (NPS) might be involved in mediating it, thus adding a neurogenetic and a neuroanatomical component to current psychological theories. We note that the rostral dACC/dmPFC shows hyper-reactivity to disease-relevant stimulation, as well as gray matter volume reduction in PD patients compared with healthy controls,32, 33, 34, 35 further strengthening the link between dACC/dmPFC-dependent processing and PD. We also note that replacing negative appraisals of an anxiogenic situation by positive ones by a deliberate emotion regulation effort attenuates anxiety-related rostral dACC/dmPFC activation,36 as would be expected if this area supported negative threat appraisal. Finally, it is remarkable that the only part of the mPFC where rats show NPS receptor expression is a dorsal site37 that has previously been implicated in attention- and working memory-related fear processing.38 Taken together, our findings provide a rich set of hypotheses for further investigation. In particular, they warrant studies in PD patients that should test whether a similar genetically modulated dissociation between physiological CRs and their explicit subjective evaluation can also be observed in the patient and whether this is associated with selective rostro-medial activation during threat situations.
Normally, bodily and cognitive CR components should be expected to behave in parallel, that is, the more one reacts at a physiological level the higher one should rate his/her responses; conversely—and of importance for cognitive theorizing—the more one thinks one is afraid or threatened, the more one's bodily response system should react. We however observed that T carriers did not show enhanced SCRs compared with AA homozygotes, although they reported higher fear. This finding seems counter-intuitive and in contradiction with cognitive theories of panic but also with multitudinous findings from appraisal research, which conclusively demonstrate the influence of evaluation processes on emotional responding.39, 40 One possibility to resolve this apparent contradiction is to assume insufficient sensitivity of our SCR method in detecting physiological genotype group differences. This explanation is unlikely given that the method is sensitive enough to detect CS+ vs CS− response differences, as well as their extinction and reacquisition, and that T carriers tended to have smaller, rather than bigger, SCRs than AA homozygotes during both acquisition and extinction. Further, it appears difficult to explain a strong effect in fear ratings (F=8.98, P=0.004) on the basis of a potential subtle, hidden SCR effect, especially when considering our rather large sample size. Finally, we have previously observed a similar dissociation between conscious appraisal and other physiological response measures (heart rate) in another fear paradigm in healthy volunteers.26
We therefore favor an alternative explanation that the influence of conscious appraisal on bodily fear reactions is limited as long as fear levels are moderate. This is likely to be the case in healthy normal volunteers threatened by a moderately painful stimulus of which they know it is not going to inflict physical damage and which they have under control (because they can stop the experiment whenever they like). The latter circumstances allow subjects to activate a host of cognitive reappraisals with known analgesic and anxiolytic potential,36, 41, 42, 43 which might contain the CR-exacerbating effect of realizing one's fear. Conscious appraisals may thus have to reach a level of actual catastrophizing in order to have strong effects on bodily reactions and to pass the threshold to starting a vicious cycle of mutually reinforcing appraisals and bodily responses.
To conclude, we have highlighted a novel molecular pathway to fear in humans and proposed a novel neurogenetic and anatomical explanation for individual differences in PD vulnerability. Our findings strongly advocate an in-depth investigation of the NPS system in relation to normal and pathological fear.
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We thank F Fassbinder, GW Alpers, H-C Pape, M Pessiglione and T Dresler for technical help and comments. This work was funded by the Deutsche Forschungsgemeinschaft (DFG Emmy Noether Grant KA1623/3–1 (KR, NG, MLM, RK); DFG Transregional Collaborative Research Centre grant SFB TRR 58, subproject Z2 (AR, JD)) and the UKE's complementary funding program (RK).
The authors declare no conflict of interest.
Supplementary Information accompanies the paper on the Molecular Psychiatry website
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Raczka, K., Gartmann, N., Mechias, ML. et al. A neuropeptide S receptor variant associated with overinterpretation of fear reactions: a potential neurogenetic basis for catastrophizing. Mol Psychiatry 15, 1067–1074 (2010). https://doi.org/10.1038/mp.2010.79
- panic disorder
- neuropeptide S
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