SPOILER ALERT!
~ Two sub-types of anxiety: anxious arousal and anxious apprehension
~ Anxious arousal is associated with greater activation of the right brain, which is characterized by heightened restlessness, increased heartbeats, hyperventilation, etc...
~ Anxious apprehension is associated with greater activation of the left brain, which is characterized by worrying, internal dialogue, thoughts, imagination, etc...
~ GAD (generalized anxiety disorder) is essentially driven by anxious apprehension while panic disorder is fueled by anxious arousal.
There is a growing interest for the identification of the neural correlates (i.e., how the brain is activated) and the autonomic indicators (e.g., heart rate, perspiration, breathing rate…) of anxiety. Intriguingly, the literature appears to produce conflicting results regarding the neural correlates of anxiety. For example, research suggests that anxiety is associated with hyperactivity in the left hemisphere of the brain, yet post-traumatic stress disorder (PTSD) and social phobia show greater activation in the right hemisphere.
To reconcile these inconsistencies, it was proposed to separate anxiety into two sub- types based on what the predominant components are. As a result, we can distinguish between anxious apprehension, predominantly verbal and cognitive (i.e., related to thoughts) with an emphasis on future negative events, and anxious arousal, which is characterized by autonomic activation and somatic fear response. In other words, the latter is more visceral, emphasizing a behavioral response as in PTSD, while the former is more cognitive with worry as its main component such as in generalized anxiety disorder (GAD). In support of this distinction, neuroimaging studies indicate higher activation in the left hemisphere in anxious apprehension and right hemispheric activity in anxious arousal.
Further evidence comes from a study showing that generalized anxiety disorder (GAD), which would be categorized under the anxious-apprehension sub-type, displays relatively greater left hemispheric activity. Those results are in line with previous ones since worry is the underlying pathological cognitive process in GAD as well as the main component in anxious apprehension. The autonomic indicators of worrying, by contrast, have not been satisfactorily identified, as mixed results were produced.
The current study seeks to compensate for the paucity of information in that field by distinguishing between anxious apprehension and anxious arousal. The results are consistent with previous findings implicating greater left hemispheric activation during anxious apprehension (e.g., worrying) and right hemispheric activation during anxious arousal. Extending the current research, the authors also report decreased vagal tone (i.e., low respiratory sinus arrhythmia RSA) during anxious apprehension (i.e., worrying) compared to anxious arousal. Decreased vagal tone or low RSA indicates higher sympathetic activation and decreased autonomic flexibility, which reflects overall restlessness.
Reference:
Hofmann, S. G., Moscovitch, D. A., Litz, B. T., Kim, H.-J., Davis, L. L., & Pizzagalli, D. A. (2005). The Worried Mind: Autonomic and Prefrontal Activation During Worrying. Emotion, 5(4), 464–475. https://doi.org/10.1037/1528-3542.5.4.464