Clinical Correlates of Carbon Dioxide Hypersensitivity in Children

Estrogens, age, and, neonatal stress: panic disorders and novel views on the contribution of non-medullary structures to respiratory control and CO2 responses

CO₂ is a fundamental component of living matter. This chemical signal requires close monitoring to ensure proper match between metabolic production and elimination by lung ventilation. Besides ventilatory adjustments, CO₂ can also trigger innate behavioral and physiological responses associated with fear and escape but the changes in brain CO₂/pH required to induce ventilatory adjustments are generally lower than those evoking fear and escape. However, for patients suffering from panic disorder (PD), the thresholds for CO₂-evoked hyperventilation, fear and escape are reduced and the magnitude of those reactions are excessive. To explain these clinical observations, Klein proposed the false suffocation alarm hypothesis which states that many spontaneous panics occur when the brain's suffocation monitor erroneously signals a lack of useful air, thereby maladaptively triggering an evolved suffocation alarm system. After 30 years of basic and clinical research, it is now well established that anomalies in respiratory control (including the CO₂ sensing system) are key to PD. Here, we explore how a stress-related affective disorder such as PD can disrupt respiratory control. We discuss rodent models of PD as the concepts emerging from this research has influenced our comprehension of the CO₂ chemosensitivity network, especially structure that are not located in the medulla, and how factors such as stress and biological sex modulate its functionality. Thus, elucidating why hormonal fluctuations can lead to excessive responsiveness to CO₂ offers a unique opportunity to gain insights into the neuroendocrine mechanisms regulating this key aspect of respiratory control and the pathophysiology of respiratory manifestations of PD.

Pediatric anxiety associated with altered facial emotion recognition

Multiple psychiatric disorders are associated with difficulties in facial emotion recognition. However, generalized anxiety disorder may be associated with more accurate recognition of others' emotional expressions, particularly expressions of happiness and fear, which index safety and threat. Children aged 9-14 from a community sample (N = 601) completed a facial emotion labeling task. Children's symptoms of depressive and anxiety syndromes were assessed by self- and parent-report. Elevated symptoms of generalized anxiety disorder were associated with more accurate facial emotion recognition (β = 0.16, p = 0.007), specifically recognition of happiness (β = 0.17, p = 0.002) and fear (β = 0.15, p = 0.006). Elevated depressive symptoms were associated with less accurate facial emotion recognition (β = -0.12, p = 0.018), specifically happiness (β = -0.15, p = 0.002). Elevated symptoms of separation anxiety disorder were also associated with less accurate facial emotion recognition (β = -0.16, p = 0.003), specifically happiness (β = -0.15, p = 0.006) and fear (β = -0.15, p = 0.005), which highlights the importance of distinguishing between anxiety syndromes. Results held when adjusting for child age and sex. Evidence that symptoms of generalized anxiety disorder are associated with more accurate recognition of happiness and fear is consistent with theories of heightened social vigilance and support a transdiagnostic role of facial emotion recognition that may inform the psychosocial development of youth with anxiety and depressive symptoms.

Differential Associations of Distress Tolerance and Anxiety Sensitivity With Adolescent Internalizing Psychopathology

Distress tolerance and anxiety sensitivity may differentiate among internalizing disorders, though few studies have examined differential associations of distress tolerance and anxiety sensitivity with depression and anxiety symptoms while adjusting for their intercorrelation. In an adolescent genetic epidemiological sample (ages 15-21), the present study (N = 848, 56.97% female) examined concurrent associations of distress tolerance and anxiety sensitivity with internalizing psychopathology (i.e., symptoms of depression, anxiety, and general stress) at baseline and prospective, predictive associations of baseline distress tolerance and anxiety sensitivity with internalizing psychopathology at 2-year follow-up. In addition, the present study assessed distress tolerance with two laboratory-based tasks, a carbon dioxide challenge and the mirror-tracing task, to distinguish between tolerance of physiological and cognitive distress, respectively. Elevated anxiety sensitivity was broadly associated with elevated symptoms of internalizing psychopathology at baseline and prospectively predicted elevated depression, anxiety, and stress symptoms at 2-year follow-up. Higher tolerance of cognitive distress was associated with lower concurrent anxiety symptoms but not with anxiety symptoms at follow-up. The present results clarify previously mixed findings; during adolescence, anxiety sensitivity showed broad concurrent and prospective associations with internalizing disorder risk whereas distress tolerance, specifically regarding cognitive distress, was associated with only elevated concurrent anxiety symptoms.

A Developmental Twin Study of Emotion Recognition and Its Negative Affective Clinical Correlates

OBJECTIVE

Youth with psychiatric disorders distinguished by irritability, including depression and associated trait neuroticism, show deficits in the ability to recognize facial expressions of emotion, particularly happiness. However, the contribution of genetic and environmental factors to this ability remains unknown. The present study examined this trait in twins to assess the genetic and environmental influences on face-emotion recognition abilities and their association with irritability, neuroticism, and depression.

METHOD

Child and adolescent twins (N = 957 from 496 families) 9 to 17 years old rated their irritability (on the Affective Reactivity Index), neuroticism (on the Junior Eysenck Personality Questionnaire), and depression (on the Short Mood and Feelings Questionnaire) and completed a face-emotion labeling task. Faces depicting anger, disgust, fear, happiness, sadness, and surprise were morphed with a neutral face, yielding 10 levels of increasing emotional expressivity. Biometrical twin analyses evaluated contributions of genetic and environmental factors to the etiology of face-emotion recognition and its association with irritability, neuroticism, and depression.

RESULTS

Recognition of each emotion was heritable; common and specific sets of genetic factors influenced all emotions and individual emotions, respectively. Irritability, neuroticism, and depression were modestly and negatively correlated with emotion recognition, particularly the recognition of happiness. For irritability and neuroticism, this correlation appeared largely due to genetic factors.

CONCLUSION

This study maps genetic and environmental contributions to face-emotion recognition and its association with irritability, neuroticism, and depression. Findings implicate common genetic factors in deficits regarding the recognition of happiness associated with irritability and neuroticism in childhood and adolescence.