Imbalance of approach and avoidance: the yin and yang of anxiety disorders

Anxiety genetics - findings from cross-species genome-wide approaches

Anxiety disorders are complex diseases, which often occur in combination with major depression, alcohol use disorder, or general medical conditions. Anxiety disorders were the most common mental disorders within the EU states in 2010 with 14% prevalence. Anxiety disorders are triggered by environmental factors in genetically susceptible individuals, and therefore genetic research offers a great route to unravel molecular basis of these diseases. As anxiety is an evolutionarily conserved response, mouse models can be used to carry out genome-wide searches for specific genes in a setting that controls for the environmental factors. In this review, we discuss translational approaches that aim to bridge results from unbiased genome-wide screens using mouse models to anxiety disorders in humans. Several methods, such as quantitative trait locus mapping, gene expression profiling, and proteomics, have been used in various mouse models of anxiety to identify genes that regulate anxiety or play a role in maintaining pathological anxiety. We first discuss briefly the evolutionary background of anxiety, which justifies cross-species approaches. We then describe how several genes have been identified through genome-wide methods in mouse models and subsequently investigated in human anxiety disorder samples as candidate genes. These studies have led to the identification of completely novel biological pathways that regulate anxiety in mice and humans, and that can be further investigated as targets for therapy.

Attention biases in female survivors of chronic interpersonal violence: relationship to trauma-related symptoms and physiology

BACKGROUND

Exposure to chronic interpersonal violence (IPV) has been associated with psychiatric impairment; however, few studies have investigated attention processes and psychophysiology in this population.

OBJECTIVE

We investigated self-report and physiological correlates of attention biases in 27 IPV-exposed women.

METHOD

Participants completed self-report measures of trauma history, posttraumatic stress disorder (PTSD) symptoms, and dissociation; were monitored physiologically during baseline; and responded to an emotional dot probe task.

RESULTS

Participants showed bias away from positive and anxiety words, and toward IPV words. Lower baseline respiratory sinus arrhythmia (RSA) and higher skin conductance levels were associated with bias away from anxiety cues. Greater total PTSD symptoms were associated with bias toward IPV cues, and greater PTSD intrusion and avoidance symptoms were associated with lower RSA. Individuals exposed to more types of trauma had lower heart rates.

CONCLUSIONS

These data extend the research on emotion-cognition interactions in PTSD and other anxiety disorders to chronic IPV survivors, in part confirming avoidance and intrusion symptom and attention bias relations found in studies. The present work also draws attention to a group that tends to experience a range of severe symptoms associated with apparent blunting in autonomic activity, and suggests that self-report may not be sensitive to physiological and attention alterations in chronic IPV samples.

Affect and state dysregulation as moderators of the relationship between childhood sexual abuse and nonsuicidal self-injury

Nonsuicidal self-injury (NSSI) is a significant problem in both clinical and nonclinical populations. Affect and state dysregulation are frequently observed in survivors of childhood sexual abuse and in those who engage in NSSI. Both have been found to predict NSSI, and affect regulation has also been modeled as a mediator of NSSI. This study extends present research by modeling both affect and state dysregulation as moderators of NSSI. The findings are discussed as an extension of the tension reduction theory and within a conceptualization of posttraumatic stress disorder (PTSD) as an asymmetry of the approach-avoidance neurophysiological system.

Heterogeneity of posttraumatic stress symptoms in a highly traumatized low income, urban, African American sample

Trauma is associated with a range of outcomes; identification of homogeneous profiles of posttrauma symptoms may inform theory, diagnostic refinement, and intervention. The present investigation applies a novel analytic technique to the identification of homogeneous subgroups of post-traumatic symptomatology in a large sample of African American adults reporting high levels of trauma. Latent profiles of posttraumatic stress disorder (PTSD) symptom severity were tested using latent profile analysis. Pseudo-class draws were used to characterize class differences across types of trauma, diagnostic comorbidities, and clinically-relevant features. Participants consisted of 2915 highly traumatized African Americans living in low income, urban setting and recruited from medical clinics in Atlanta, GA. Findings supported the presence of six distinct subgroups of posttraumatic stress symptom profiles described as resilient, moderate with amnesia, moderate with diminished interest, moderate without diminished interest and amnesia severe without amnesia, and severe overall. Observed subgroups differed across numerous historical and concurrent factors including childhood trauma, current and lifetime diagnoses of PTSD and major depression, lifetime substance use diagnosis, dissociation, depressive symptoms, emotional dysregulation, negative and positive affect, and history of hospitalization and suicidality. Posttraumatic stress disorder as currently defined is comprised of homogeneous subgroups with important differences in posttraumatic stress symptom endorsement as well as concomitant differentiation of associated diagnoses and clinically-relevant associated features.

Increased neural habituation in the amygdala and orbitofrontal cortex in social anxiety disorder revealed by FMRI

A characterizing symptom of social anxiety disorder (SAD) is increased emotional reactivity towards potential social threat in combination with impaired emotion and stress regulation. While several neuroimaging studies have linked SAD with hyperreactivity in limbic brain regions when exposed to emotional faces, little is known about habituation in both the amygdala and neocortical regulation areas. 15 untreated SAD patients and 15 age- and gender-matched healthy controls underwent functional magnetic resonance imaging during repeated blocks of facial emotion ([Formula: see text]) and object discrimination tasks ([Formula: see text]). Emotion processing networks were defined by a task-related contrast ([Formula: see text]). Linear regression was employed for assessing habituation effects in these regions. In both groups, the employed paradigm robustly activated the emotion processing and regulation network, including the amygdalae and orbitofrontal cortex (OFC). Statistically significant habituation effects were found in the amygdalae, OFC, and pulvinar thalamus of SAD patients. No such habituation was found in healthy controls. Concurrent habituation in the medial OFC and the amygdalae of SAD patients as shown in this study suggests intact functional integrity and successful short-term down-regulation of neural activation in brain areas responsible for emotion processing. Initial hyperactivation may be explained by an insufficient habituation to new stimuli during the first seconds of exposure. In addition, our results highlight the relevance of the orbitofrontal cortex in social anxiety disorders.

Cumulative adversity and smaller gray matter volume in medial prefrontal, anterior cingulate, and insula regions

BACKGROUND

Cumulative adversity and stress are associated with risk of psychiatric disorders. While basic science studies show repeated and chronic stress effects on prefrontal and limbic neurons, human studies examining cumulative stress and effects on brain morphology are rare. Thus, we assessed whether cumulative adversity is associated with differences in gray matter volume, particularly in regions regulating emotion, self-control, and top-down processing in a community sample.

METHODS

One hundred three healthy community participants, aged 18 to 48 and 68% male, completed interview assessment of cumulative adversity and a structural magnetic resonance imaging protocol. Whole-brain voxel-based-morphometry analysis was performed adjusting for age, gender, and total intracranial volume.

RESULTS

Cumulative adversity was associated with smaller volume in medial prefrontal cortex (PFC), insular cortex, and subgenual anterior cingulate regions (familywise error corrected, p < .001). Recent stressful life events were associated with smaller volume in two clusters: the medial PFC and the right insula. Life trauma was associated with smaller volume in the medial PFC, anterior cingulate, and subgenual regions. The interaction of greater subjective chronic stress and greater cumulative life events was associated with smaller volume in the orbitofrontal cortex, insula, and anterior and subgenual cingulate regions.

CONCLUSIONS

Current results demonstrate that increasing cumulative exposure to adverse life events is associated with smaller gray matter volume in key prefrontal and limbic regions involved in stress, emotion and reward regulation, and impulse control. These differences found in community participants may serve to mediate vulnerability to depression, addiction, and other stress-related psychopathology.

An fMRI study of unconditioned responses in post-traumatic stress disorder

BACKGROUND

Both fear and pain processing are altered in post-traumatic stress disorder (PTSD), as evidenced by functional neuroimaging studies showing increased amygdala responses to threats, and increased insula, putamen and caudate activity in response to heat pain. Using psychophysiology and functional magnetic resonance imaging, we studied conditioned and unconditioned autonomic and neuronal responses in subjects with PTSD versus trauma-exposed non-PTSD control (TENC) subjects. A design using an electric shock selected by subjects to be 'highly annoying but not painful' as an unconditioned stimulus (US) with partially reinforced cues allowed us to partly disentangle the expectancy- and prediction-error components from sensory components of the unconditioned response.

RESULTS

Whereas responses to the conditioned stimulus (CS) were similar in PTSD and TENC, the former displayed higher putamen, insula, caudate and amygdala responses to the US. Reactivity to the US in the anterior insula correlated with PTSD symptom severity. Functional connectivity analyses using the putamen as a seed region indicated that TENC subjects had increased amygdala-putamen connectivity during US delivery; this connection was disengaged in PTSD.

CONCLUSIONS

Our results indicate that although neural processing of fear learning in people with PTSD seems to be comparable with controls, neural responses to unconditioned aversive stimuli in PTSD seem to be increased.

A reverse translational approach to quantify approach-avoidance conflict in humans

Animal approach-avoidance conflict paradigms have been used extensively to characterize effects of anxiolytic agents and probe neural circuitry related to anxiety. However, there are few behavioral approaches to measure conflict in human populations, limiting the translation of findings from animal conflict tasks to human clinical research. We developed a novel approach-avoidance conflict (AAC) paradigm involving situations in which the same decision is associated with "reward" (points) and "punishment" (negative affective stimuli). The AAC task was completed by 95 young adults (56 female) with varying levels of self-reported trait anxiety. As expected, conflict-related approach behavior correlated with self-reported motivation to approach reward and avoid punishment and greater reward level increased approach behavior. Additionally, females exhibited less approach behavior than males. Anxiety Sensitivity Index (Physical subscale) scores related negatively to approach behavior for males, while Behavioral Activation Scale (BAS, Fun Seeking subscale) scores related positively to approach behavior for females. Results support the utility of the AAC task as a behavioral test that has strong reverse translational features. Findings indicate that approach drives and anxiety sensitivity may be important in determining conflict behavior for females and males respectively. The approach-avoidance conflict task offers a novel, translational measure to probe neural systems underlying conflict behavior, motivational processes, and anxiety disorders.

Human avoidance and approach learning: evidence for overlapping neural systems and experiential avoidance modulation of avoidance neurocircuitry

Adaptive functioning is thought to reflect a balance between approach and avoidance neural systems with imbalances often producing pathological forms of avoidance. Yet little evidence is available in healthy adults demonstrating a balance between approach and avoidance neural systems and modulation in avoidance neurocircuitry by vulnerability factors for avoidance. Consequently, we used functional magnetic resonance imaging (fMRI) to compare changes in brain activation associated with human avoidance and approach learning and modulation of avoidance neurocircuitry by experiential avoidance. fMRI tracked trial-by-trial increases in activation while adults learned through trial and error an avoidance response that prevented money loss and an approach response that produced money gain. Avoidance and approach cues elicited similar experience-dependent increases in activation in a fronto-limbic-striatal network. Positive and negative reinforcing outcomes (i.e., money gain and avoidance of loss) also elicited similar increases in activation in frontal and striatal regions. Finally, increased experiential avoidance and self-punishment coping was associated with decreased activation in medial/superior frontal regions, anterior cingulate, amygdala and hippocampus. These findings suggest avoidance and approach learning recruit a similar fronto-limbic-striatal network in healthy adults. Increased experiential avoidance also appears to be associated with reduced frontal and limbic reactivity in avoidance, establishing an important link between maladaptive avoidance coping and altered responses in avoidance neurocircuitry.

Imaging in posttraumatic stress disorder

PURPOSE OF REVIEW

Posttraumatic stress disorder (PTSD) is an unusual diagnosis in requiring an external environmental stressor to be present, in addition to the conventional signs and symptoms. Early controversies surrounded the validity of its criteria and whether there was a common neural basis for this disorder. This review summarizes recent neuroimaging studies, which have begun to clarify the basis of PTSD by combining imaging data with investigations of the stress response, and by employing fear and extinction learning paradigms to probe the underlying neural changes in those with the disorder.

RECENT FINDINGS

We examine the recent literature with three main aims. First, to assess whether structural changes in PTSD are causal of or secondary to the condition. Second, to summarize current understanding of the relationship between neural activation and the stress responses within the autonomic nervous system in PTSD patients and controls. Finally, we examine neural mechanisms underlying the response to fear and reward, demonstrating how these are altered in PTSD.

SUMMARY

A greater understanding of the brain mechanisms underlying healthy responses to fear and stress, and their alterations in PTSD, has opened up a new spectrum of possible pharmacological agents by which to approach to PTSD therapy and has begun to reveal the neural processes underlying the common failure of response to current treatments.