Attenuation of Anxiety-Potentiated Startle After Treatment With Escitalopram or Mindfulness Meditation in Anxiety Disorders.

BACKGROUND: Biological markers for anxiety disorders may further understanding of disorder pathophysiology and suggest potential targeted treatments. The fear-potentiated startle (FPS) (a measure of startle to predictable threat) and anxiety-potentiated startle (APS) (startle to unpredictable threat) laboratory paradigm has been used to detect physiological differences in individuals with anxiety disorders compared with nonanxious control individuals, and in pharmacological challenge studies in healthy adults. However, little is known about how startle may change with treatment for anxiety disorders, and no data are available regarding alterations due to mindfulness meditation training. METHODS: Ninety-three individuals with anxiety disorders and 66 healthy individuals completed 2 sessions of the neutral, predictable, and unpredictable threat task, which employs a startle probe and the threat of shock to assess moment-by-moment fear and anxiety. Between the two testing sessions, patients received randomized 8-week treatment with either escitalopram or mindfulness-based stress reduction. RESULTS: APS, but not FPS, was higher in participants with anxiety disorders compared with healthy control individuals at baseline. Further, there was a significantly greater decrease in APS for both treatment groups compared with the control group, with the patient groups showing reductions bringing them into the range of control individuals at the end of the treatment. CONCLUSIONS: Both anxiety treatments (escitalopram and mindfulness-based stress reduction) reduced startle potentiation during unpredictable (APS) but not predictable (FPS) threat. These findings further validate APS as a biological correlate of pathological anxiety and provide physiological evidence for the impact of mindfulness-based stress reduction on anxiety disorders, suggesting that there may be comparable effects of the two treatments on anxiety neurocircuitry.

Responding to uncertain threat: A potential mediator for the effect of mindfulness on anxiety.

Mindfulness-based interventions have gained extensive support for their application in the treatment of anxiety. However, their mechanisms remain largely unexplored. Excessive reactivity to uncertainty plays a central role in anxiety, and may represent a mechanism for the effect of mindfulness on anxiety, as mindfulness training fosters an open and accepting stance towards all aspects of experience. The present study sought to investigate both (i) self-reported intolerance of uncertainty (IU) as well as (ii) physiological and subjective responding to uncertain threat in a threat-of-shock paradigm, the NPU-threat test, as mediators for the relationship between mindfulness and anxiety in a cross-sectional study of healthy participants (N = 53). The results indicated that IU mediated the effect of mindfulness on some anxiety symptoms. In contrast, scores of physiological as well as subjective responses to uncertain threat from the NPU-threat test were largely unrelated to mindfulness, anxiety, or the IU self-report measure. The results provide initial evidence that reactions to uncertainty may play a role in the mindfulness-anxiety relationship and suggest that studies are needed to address how methodological variations of the NPU-threat test affect perceived levels of uncertainty and uncertainty-related anxiety.

Intrinsic connections between thalamic sub-regions and the lateral prefrontal cortex are differentially impacted by acute methylphenidate.

BACKGROUND: The thalamus is a major target of dopaminergic projections and is densely connected with the prefrontal cortex. A better understanding of how dopamine changes thalamo-cortical communication may shed light on how dopamine supports cognitive function. Methylphenidate has been shown to facilitate cognitive processing and reduce connectivity between the thalamus and lateral prefrontal cortex. AIMS: The thalamus is a heterogeneous structure, and the present study sought to clarify how the intrinsic connections of thalamic sub-regions are differentially impacted by acute dopamine transporter blockade. METHODS: Sixty healthy volunteers were orally administered either 20 mg of methylphenidate (N = 29) or placebo (N = 31) in a double-blind, randomized, between-subject design. Multi-echo fMRI was used to assess intrinsic functional connectivity of sub-regions of the thalamus during a resting state scan. An N-back working-memory paradigm provided a measure of cognitive performance. RESULTS: Acute methylphenidate significantly reduced connectivity of the lateral prefrontal cortex with the motor and somatosensory sub-regions of the thalamus and reduced connectivity with the parietal and visual sub-regions at a trend level. Connectivity with the premotor, prefrontal, and temporal sub-regions was not impacted. The intrinsic connectivity between the thalamus and the lateral prefrontal cortex was not associated with working-memory performance. CONCLUSIONS: Methylphenidate decreases functional connections between the lateral prefrontal cortex and thalamus broadly, while sparing intrinsic connectivity with thalamic sub-regions involved with working-memory and language related processes. Collectively, our results suggest that the dopamine transporter regulates functional connections between the prefrontal cortex and non-cognitive areas of the thalamus.

Startling Differences: Using the Acoustic Startle Response to Study Sex Differences and Neurosteroids in Affective Disorders.

PURPOSE OF REVIEW: Neuroactive steroid hormones, such as estradiol and progesterone, likely play a role in the pathophysiology of female-specific psychiatric disorders such as premenstrual dysphoric disorder (PMDD) and postpartum depression and may contribute to the marked sex differences observed in the incidence and presentation of affective disorders. However, few tools are available to study the precise contributions of these neuroactive steroids (NSs). In this review, we propose that the acoustic startle response (ASR), an objective measure of an organism's response to an emotional context or stressor, is sensitive to NSs. As such, the ASR represents a unique translational tool that may help to elucidate the contribution of NSs to sex differences in psychiatric disorders. RECENT FINDINGS: Findings suggest that anxiety-potentiated startle (APS) and prepulse inhibition of startle (PPI) are the most robust ASR paradigms for assessing contribution of NSs to affective disorders, while affective startle response modulation (ASRM) appears less diagnostic of sex or menstrual cycle (MC) effects. However, few studies have appropriately used ASR to test a priori hypotheses about sex or MC differences. We recommend that ASR studies account for sex as a biological variable (SABV) and hormonal status to further knowledge of NS contribution to affective disorders.

Extended amygdala connectivity changes during sustained shock anticipation.

The bed nucleus of the stria terminalis (BNST) and central amygdala (CeA) of the extended amygdala are small, anatomically interconnected brain regions. They are thought to mediate responses to sustained, unpredictable threat stimuli and phasic, predictable threat stimuli, respectively. They perform these operations largely through their interconnected networks. In two previous studies, we mapped and contrasted the resting functional connectivity networks of the BNST and CeA at 7 Tesla with high resolution. This follow-up study investigates the changes in functional connectivity of these structures during sustained anticipation of electric shock. Results show that the BNST and CeA become less strongly coupled with the ventromedial prefrontal cortex (vmPFC), cingulate, and nucleus accumbens in shock threat relative to a safety condition. In addition, the CeA becomes more strongly coupled with the thalamus under threat. An exploratory, whole-brain connectivity analysis reveals that, although the BNST/CeA exhibits generally decreased connectivity, many other cortical regions demonstrate greater coupling under threat than safety. Understanding the differential network structures of these two regions and how they contribute to processing under threat will help elucidate the building blocks of the anxious state.

The CRH1 antagonist GSK561679 increases human fear but not anxiety as assessed by startle.

Fear to predictable threat and anxiety to unpredictable threat reflect distinct processes mediated by different brain structures, the central nucleus of the amygdala and the bed nucleus of the stria terminalis (BNST), respectively. This study tested the hypothesis that the corticotropin-releasing factor (CRF1) antagonist GSK561679 differentially reduces anxiety but increases fear in humans. A total of 31 healthy females received each of four treatments: placebo, 50 mg GSK561679 (low-GSK), 400 mg GSK561679 (high-GSK), and 1 mg alprazolam in a crossover design. Participants were exposed to three conditions during each of the four treatments. The three conditions included one in which predictable aversive shocks were signaled by a cue, a second during which shocks were administered unpredictably, and a third condition without shock. Fear and anxiety were assessed using the acoustic startle reflex. High-GSK had no effect on startle potentiation during unpredictable threat (anxiety) but increased startle potentiation during the predictable condition (fear). Low-GSK did not affect startle potentiation across conditions. Consistent with previous findings, alprazolam reduced startle potentiation during unpredictable threat but not during predictable threat. The increased fear by high-GSK replicates animal findings and suggests a lift of the inhibitory effect of the BNST on the amygdala by the CRF1 antagonist.

Developmental investigation of fear-potentiated startle across puberty.

The goal of this study was to examine the association between affective development, puberty, and gender using the startle reflex as a marker of defensive mechanisms. Thirty-one male and thirty-five female adolescents aged ten to thirteen participated in a prospective study with up to five assessments. Longitudinal analyses revealed a significant effect of sex, with girls showing stronger fear-potentiation at all pubertal stages. Post hoc tests revealed that fear-potentiation increased in girls but not boys over the course of puberty. Furthermore, baseline startle decreased over the course of puberty. Because age was included as a covariate in all analyses, the puberty effect cannot be accounted for by age. To the best of our knowledge, this study provides the first evidence for a significant increase in fear-potentiated startle across the pubertal transition. Attribution of these changes to pubertal status rather than age has important implications for our understanding of the neurobiology of anxiety and affect regulation.

Acute hydrocortisone treatment increases anxiety but not fear in healthy volunteers: a fear-potentiated startle study.

BACKGROUND: The debilitating effects of chronic glucocorticoids excess are well-known, but comparatively little is understood about the role of acute cortisol. Indirect evidence in rodents suggests that acute cortisone could selectively increase some forms of long-duration aversive states, such as "anxiety," but not relatively similar, briefer aversive states, such as "fear." However, no prior experimental studies in humans consider the unique effects of cortisol on anxiety and fear, using well-validated methods for eliciting these two similar but dissociable aversive states. The current study examines these effects, as instantiated with short- and long-duration threats. METHODS: Healthy volunteers (n = 18) received placebo or a low (20 mg) or a high (60 mg) dose of hydrocortisone in a double-blind crossover design. Subjects were exposed repeatedly to three 150-sec duration conditions: no shock; predictable shocks, in which shocks were signaled by a short-duration threat cue; and unpredictable shocks. Aversive states were indexed by acoustic startle. Fear was operationally defined as the increase in startle reactivity during the threat cue in the predictable condition (fear-potentiated startle). Anxiety was operationally defined as the increase in baseline startle from the no shock to the two threat conditions (anxiety-potentiated startle). RESULTS: Hydrocortisone affected neither baseline nor short-duration, fear-potentiated startle but increased long-duration anxiety-potentiated startle. CONCLUSIONS: These results suggest that hydrocortisone administration in humans selectively increases anxiety but not fear. Possible mechanisms implicated are discussed in light of prior data in rodents. Specifically, hydrocortisone might increase anxiety via sensitization of corticotrophin-releasing hormones in the bed nucleus of the stria terminalis.

Increased anxiety during anticipation of unpredictable aversive stimuli in posttraumatic stress disorder but not in generalized anxiety disorder.

BACKGROUND: Uncontrollability and unpredictability are key concepts related to re-experiencing, avoidance, and hypervigilance symptoms of posttraumatic stress disorder (PTSD). However, little is known about the differential sensitivity of PTSD individuals to unpredictable stressors, relative to either healthy individuals or individuals with other anxiety disorders. This study tested the hypothesis that elevated anxious reactivity, specifically for unpredictable aversive events, is a psychophysiological correlate of PTSD. METHODS: Sixteen patients with PTSD (34.5 +/- 12.4 years) were compared with 18 patients with generalized anxiety disorder (GAD) (34.0 +/- 10.5 years) and 34 healthy control subjects (30.2 +/- 8.5 years). Participants were exposed to three conditions: one in which predictable aversive stimuli were signaled by a cue, a second in which aversive stimuli were administered unpredictably, and a third in which no aversive stimuli were anticipated. Startle magnitude was used to assess anxious responses to the threat cue and to contexts associated with each condition. RESULTS: Posttraumatic stress disorder and GAD patients showed normative enhancement of fear to the predictable threat cue, but the PTSD group displayed elevated anxiety during the unpredictable condition compared with participants with GAD and healthy control subjects. CONCLUSIONS: Anxious reactivity to unpredictable aversive events was heightened in PTSD but not in GAD and healthy subjects. Prior works also found signs of increased reactivity to unpredictable threat in panic disorder (PD), suggesting that PTSD and PD may involve shared vulnerability. As such, the current results inform understandings of classification, pathophysiology, and psychopharmacology of anxiety disorders, generally, and PTSD and panic disorder specifically.

Two-week treatment with the selective serotonin reuptake inhibitor citalopram reduces contextual anxiety but not cued fear in healthy volunteers: a fear-potentiated startle study.

Chronic treatment with selective serotonin reuptake inhibitors (SSRIs) alleviates both anxiety symptoms and associated physiologic disturbances in anxious patients. However, limited research considers the degree to which chronic SSRI treatment influences anxiety in healthy individuals. This study examined the effect of 2-week citalopram treatment on two threat responses: short- and long-duration-potentiated startle. Prior work suggests that these two responses provide neurally and functionally distinct models of fear and anxiety, respectively, in rodents. Healthy volunteers (n=53) received either placebo or citalopram (20 mg per day) for 2 weeks under double-blind conditions. They were each tested twice, before and after treatment. Participants were exposed to three conditions, including one in which predictable aversive shocks were signaled by a cue, a second in which unpredictable shocks were anticipated, and a third in which no shocks were administered. Aversive states were indexed by acoustic startle. Phasic fear-potentiated startle to the threat cue, as well as sustained startle potentiation to the experimental context in the predictable and unpredictable conditions, were investigated. Citalopram affected neither baseline startle nor short-duration fear-potentiated startle to discrete threat cues. However, citalopram reduced long-duration startle potentiation in the predictable conditions. These results are consistent with the hypothesis that short- and long-duration aversive states are mediated by distinct neural systems. They suggest that citalopram alleviates symptoms of anticipatory anxiety, not fear, by acting on mechanisms underlying long-duration aversive states.

Startle reactivity in children at risk for migraine.

OBJECTIVE: Numerous studies have shown a higher responsiveness and/or a lack of habituation to sensory stimuli of various modalities in migraine. This study investigated psychophysiological responses to aversive acoustic stimuli in children at risk for migraine. METHODS: We measured eyeblink responses to acoustic stimuli (40ms bursts of white noise at 102dB) during anticipation of unpleasant stimuli in 74 adolescents (40 females, age 17.6+/-2.9). A mixed effects linear model was applied to test group differences in startle reactivity during baseline, safe and threat conditions among adolescents by maternal and personal history of migraine. RESULTS: The strongest association with migraine vulnerability emerged for baseline startle reactivity, which was significantly elevated in high risk youth with a history of maternal migraine. This group of offspring also had enhanced startle response during the threat condition and the threat-safe difference. CONCLUSION: Our findings indicate that migraine is associated with a higher acoustic startle responsiveness that is present already in children at risk for developing the disorder. SIGNIFICANCE: The significant effect of both maternal history of anxiety disorder and migraine on baseline startle indicates that these two diagnostic entities might in part share common pathophysiological mechanisms, and that the anxiety-migraine comorbidity should be considered when investigating each of these disorders.

Modality-specific attention under imminent but not remote threat of shock: evidence from differential prepulse inhibition of startle.

Theories of animal defensive behavior postulate that imminent, predictable threat elicits highly focused attention toward the threat source, whereas remote, unpredictable threat elicits distributed attention to the overall environment. We used threat of shock combined with measurement of prepulse inhibition of the startle reflex to test these claims in humans. Twenty-seven participants experienced periods of threat and safety. Threat and safe periods were short or long, with the short threat periods conveying relatively predictable, imminent shocks and the long threat periods conveying unpredictable shocks. Startle reflexes were elicited with equal numbers of acoustic probes presented alone, preceded by a tactile prepulse, or preceded by an auditory prepulse. We observed enhanced tactile relative to auditory prepulse inhibition during short threat periods only. This finding supports the notion that imminent threat, but not remote threat, elicits attention focused toward the relevant modality, potentially reflecting preparatory activity to minimize the impact of the noxious stimulus.

Fear conditioning in adolescents with anxiety disorders: results from a novel experimental paradigm.

OBJECTIVE: Considerable research examines fear conditioning in adult anxiety disorders but few studies examine youths. Adult data suggest that anxiety disorders involve elevated fear but intact differential conditioning. We used a novel paradigm to assess fear conditioning in pediatric anxiety patients. METHOD: Sixteen individuals with anxiety disorders and 38 healthy comparisons viewed two photographs of actresses displaying neutral expressions. One picture served as the conditioned stimulus (CS), paired with a fearful expression and a shrieking scream (CS+), whereas the other picture served as a CS unpaired with the aversive outcome (CS-). Conditioning was indexed by self-reported fear. Subjects participated in two visits involving conditioning and extinction trials. RESULTS: Both groups developed greater fear of the CS+ relative to CS-. Higher fear levels collapsed across each CS characterized anxious relative to healthy subjects, but no significant interaction between group and stimulus type emerged. Fear levels at visit 1 predicted avoidance of visit 2. Fear levels to both CS types showed stability even after extinction. CONCLUSIONS: Consistent with adult data, pediatric anxiety involves higher fear levels following conditioning but not greater differential conditioning. Extending these methods to neuroimaging studies may elucidate neural correlates of fear conditioning. Implications for exposure therapies are discussed.

Neural responses to auditory stimulus deviance under threat of electric shock revealed by spatially-filtered magnetoencephalography.

Stimulus novelty or deviance may be especially salient in anxiety-related states due to sensitization to environmental change, a key symptom of anxiety disorders such as posttraumatic stress disorder (PTSD). We aimed to identify human brain regions that show potentiated responses to stimulus deviance during anticipatory anxiety. Twenty participants (14 men) were presented a passive oddball auditory task in which they were exposed to uniform auditory stimulation of tones with occasional deviations in tone frequency, a procedure that elicits the mismatch negativity (MMN) and its magnetic counterpart (MMNm). These stimuli were presented during threat periods when participants anticipated unpleasant electric shocks, and safe periods when no shocks were anticipated. Neuromagnetic data were collected with a 275-channel whole-head MEG system and event-related beamformer analyses were conducted to estimate source power across the brain in response to stimulus deviance. Source analyses revealed greater right auditory and inferior parietal activity to stimulus deviance under threat relative to safe conditions, consistent with locations of MMN and MMNm sources identified in other studies. Structures related to evaluation of threat, left amygdala and right insula, also showed increased activity to stimulus deviance under threat. As anxiety level increased across participants, right and left auditory cortical as well as right amygdala activity increased to stimulus deviance. These findings fit with evidence of a potentiated MMN in PTSD relative to healthy controls, and warrant closer evaluation of how these structures might form a functional network mediating sensitization to stimulus deviance during anticipatory anxiety.

Fear-potentiated startle to threat, and prepulse inhibition among young adult nonsmokers, abstinent smokers, and nonabstinent smokers.

BACKGROUND: Evidence suggests that the transition from experimental to regular smoking is facilitated by the influence of tobacco on affective and attentional mechanisms. The objective of this study was to examine affective and attentional responses in young adult smokers using fear-potentiated startle and prepulse inhibition. METHODS: Participants were 56 college nonsmokers, nonabstinent smokers, and overnight-abstinent smokers. The fear-potentiated startle test examined phasic responses to imminent threat cues and more sustained responses to unpredictable aversive events. Prepulse inhibition investigated responses to attended and ignored prepulse stimuli. RESULTS: Abstinent and nonabstinent smokers showed increased sustained potentiation of startle to contextual cues, compared to controls. Abstinent smokers showed increased fear-potentiated startle to threat cues, compared to nonsmokers. PPI did not discriminate between abstinent or nonabstinent smokers and controls. CONCLUSIONS: These findings suggest that negative affectivity or anxiety is associated with smoking, particularly during short withdrawal. Potentiated startle may provide a valuable tool in understanding the biologic mechanisms underlying nicotine withdrawal and inform cessation and prevention efforts.

Luteal-phase accentuation of acoustic startle response in women with premenstrual dysphoric disorder.

Alterations in central nervous system response to menstrual cycle-related fluctuations in neuroactive steroids are thought to underlie the emergence of negative affect in the luteal phase of the menstrual cycle in women with premenstrual dysphoric disorder (PMDD). Such changes in the neuroendocrine milieu may lead to heightened arousal and response to stress in women with PMDD. Using the acoustic startle paradigm, we sought to determine whether women with PMDD have an accentuated physiologic response to a mildly aversive stimulus during the luteal compared to follicular phase. Further, we also examined the impact of visual affective stimuli on acoustic startle response (ASR) magnitude. During the follicular and luteal phases of the menstrual cycle, acoustic stimuli (103 dB) were delivered to 15 women with PMDD and 14 healthy menstruating women of similar age. After obtaining baseline ASR, the procedure was repeated when subjects viewed pleasant, neutral and unpleasant pictures. There was a significant group by menstrual cycle phase interaction for baseline ASR magnitude, which can be attributed to the heightened startle magnitude in women with PMDD compared to healthy women during the luteal relative to the follicular phase. The direction and degree to which picture viewing modulated the startle magnitude did not vary by group or menstrual cycle phase. These data suggest that menstrual cycle phase has a powerful modulatory effect on physiologic reactivity in women with PMDD but not in healthy women. Physiologic response to affective stimuli appears to be intact in women with PMDD across the menstrual cycle.

Reduction of trace but not delay eyeblink conditioning in panic disorder.

OBJECTIVE: Individuals with panic disorder perceive panic attacks as unpredictable. Because predictability is fundamental to Pavlovian conditioning, failure to predict panic attacks could be due to a basic deficit in conditioning. The present study examined trace eyeblink conditioning in order to test the hypothesis that individuals with panic disorder are impaired in associative learning tasks that depend on declarative memory. METHOD: Delay and trace eyeblink conditioning were tested in separate experimental sessions in 19 individuals meeting DSM-IV criteria for panic disorder and 19 sex- and age-matched healthy comparison subjects. In the delay paradigm, a mild puff was delivered to the eye at the end of a 500-msec tone; in the trace paradigm, the puff was delivered after a 700-msec empty "trace" interval that followed the end of the tone. RESULTS: Patients and comparison subjects showed similar rates of conditioned responses in the delay paradigm, but patients showed reduced rates of conditioned responses in the trace paradigm. CONCLUSIONS: These results suggest that individuals with panic disorder suffer from a deficit in declarative associative learning. Such a deficit points to impaired hippocampal function that may disrupt cognitive processing of internal and external cues predictive of a panic attack.

The benzodiazepine alprazolam dissociates contextual fear from cued fear in humans as assessed by fear-potentiated startle.

BACKGROUND: The startle reflex is potentiated by aversive states. It has been proposed that phasic startle potentiation to a threat cue and sustained startle potentiation to contextual stimuli reflect distinct processes mediated by different brain structures. The present study tested the hypothesis that alprazolam would reduce the sustained startle potentiation to contextual threats but not the startle potentiation to a threat cue. METHODS: Sixteen healthy subjects received each of four treatments: placebo, .5 mg of alprazolam, 1 mg of alprazolam, and 50 mg of diphenhydramine (Benadryl) in a crossover design. Participants were exposed to three conditions, including one in which predictable aversive shocks were signaled by a cue, a second in which shocks were administered unpredictably, and a third condition in which no shocks were anticipated. Acoustic startle were delivered regularly across conditions. RESULTS: Phasic startle potentiation to the threat cue in the predictable condition was not affected by alprazolam. In contrast, the sustained increase in startle in the predictable and unpredictable conditions was reduced significantly by the high dose of alprazolam. CONCLUSIONS: Startle responses to an explicit threat cue and to an aversive context are psychopharmacologically distinct, suggesting that they may represent functionally dissociable aversive states.

Hydrocortisone impairs hippocampal-dependent trace eyeblink conditioning in post-traumatic stress disorder.

Trace eyeblink conditioning is a hippocampal-dependent associative learning task that could help evaluate hippocampal function in Post-traumatic stress disorder (PTSD). Since preclinical research has demonstrated that trace eyeblink conditioning can be pharmacologically manipulated by glucocorticoids, this task may shed light on glucocorticoid sensitivity in PTSD. This study assessed baseline and hydrocortisone-mediated changes in trace eyeblink conditioning in patients with PTSD and in healthy controls. A total of 12 patients with PTSD and 12 age- and sex-matched healthy controls participated in a trace eyeblink test 6 h following intravenous administration of 30 mg of hydrocortisone. Spontaneous blink rates were similar between PTSD patients and healthy controls. There was no significant difference in the mean conditioned response between PTSD subjects and healthy controls under placebo conditions. Following hydrocortisone administration, only the PTSD patients demonstrated a significant reduction in conditioned response in contrast to healthy subjects who did not demonstrate any change. Patients with PTSD had increased glucocorticoid sensitivity in the focal brain regions mediating trace eyeblink conditioning.

Families at high and low risk for depression: a three-generation startle study.

BACKGROUND: Anxiety symptoms might be a vulnerability factor for the development of major depressive disorder (MDD). Because elevated startle magnitude in threatening contexts is a marker for anxiety disorder, the present study investigated the hypothesis that enhanced startle reactivity would also be found in children and grandchildren of individuals with MDD. METHODS: The magnitude of startle was investigated in two tests (anticipation of an unpleasant blast of air and during darkness) in children (second generation) and grandchildren (third generation) of probands with (high risk) or without (low risk) MDD (first generation). RESULTS: Startle discriminated between the low- and high-risk groups. In the probands' children, the high-risk group showed increased startle magnitude throughout the fear-potentiated startle test. In the probands' grandchildren, a gender-specific abnormality was found in the high-risk group with high-risk girls, but not boys, exhibiting elevated startle magnitude throughout the procedure. CONCLUSIONS: Increased startle reactivity in threatening contexts, previously found in patients with anxiety disorder and in children of parents with an anxiety disorder, might also constitute a vulnerability marker for MDD. These findings suggest that there might be common biologic diatheses underlying depression and anxiety.