"When it comes to emotion, all roads lead to the autonomic nervous system” Robert W. Levenson
Recently, many clinicians are advocating for the use of the term “Emotional Dysregulation Disorder” to replace the very stigmatized “Borderline Personality Disorder.” It makes sense because, even when all personality disorders suffer from emotional dysregulation one way or another, BPD is the one that struggles the most regulating emotional responses.
The autonomic nervous system, regulated by the hypothalamus, is a control system that acts largely without our conscious participation to regulate bodily functions that behave always the same way. All those functions are supposed to be automatic and autonomous. That’s only partially true since even the most basic functions like heart rate and respiratory rate can be changed at will if we want to, and learn to.
The autonomic nervous system consists of two antagonistic sets of nerves, the sympathetic and parasympathetic nervous systems. Those 2 systems connect the brain with all the rest of the body and with each organ, sending signals to organs, glands, and spinal nerves to regulate functions; the sympathetic regulates activity, and the parasympathetic regulates digestion, stores energy, and controls rest states. Both nerve systems are in charge of keeping the system working which translates as the survival system.
According to several theories, emotions organize the activity of the autonomic nervous system (ANS) and the ANS has a critical role on the generation, expression, experience, or recognition of emotion.
Reciprocal sympathetic activation, or increases in sympathetic activity accompanied by decreases in parasympathetic activity, is associated with better regulation of emotion.
With the introduction of Polyvagal theory, the relationship between emotional dysregulation and the ANS becomes a little more complicated.
Porges changed the paradigm of the ANS by combining biology with attachment theory and evolution. The most significant differences are:
Porges differentiated between two branches of the Vagus Nerve: the ventral which is myelinated —newer, optimized, only on mammals — and the dorsal which is unmyelinated —older, primitive, shared by all vertebrates.
Porges differentiates brainstem areas that regulate the organs situated above the diaphragm (branching to the face, head, lungs, and heart) from those regulating below the diaphragm (gut), depending on the myelinated and unmyelinated vagal pathways (ramifications of the vagus nerve extends from the head to the abdomen; myelinated refers to a fat layer covering the nerve, and myelinated nerves send signals faster than an unmyelinated nerve)
Porges also notes that the ANS is a system of three circuits in which newer circuits inhibit older circuits; that the ANS functioning is hierarchical instead of antagonistic (or looking only for equilibrium); and that the newest vagus controls vocalization and face expression-recognition as an added survival strategy.
According to the polyvagal theory, the ventral vagus – the second branch of the parasympathetic nervous system and our newest evolutionary function – supports our capacity to have healthy relationships, it regulates our physiology, it is the place from which we keep ourselves safe and connected through socially engaged behavior.
With all that said, let’s put together the AND and BPD symptoms.
There is published evidence that the parasympathetic component of the ANS differentiates the response profiles between individuals diagnosed with BPD and others.
The lack of attunement with the sympathetic system of the mother (or primary caregiver) could cause the ventral vagus system of the child to become atrophied or compromised.
When the Social-engagement system regulated by the ventral vagus (part of the parasympathetic) is compromised in pwBPD it becomes difficult for them to accurately recognize facial expressions as cues for safety, which keep them in a state of hypervigilance, confusion, mistrust, and alertness.
The ventral vagus is in charge of Orienting (and Freeze) which puts the break to the activation of the fight-flight response (sympathetic). If as I said, it’s compromised and its regulation atypical, pwBPD lack the capacity to hold the fight-flight response. They go into hyperarousal much faster than people with a regulated ventral vagus, this is experienced as lack of affect tolerance, and impulsivity.
Since the amygdala is overactive in pwBPD, the sympathetic and parasympathetic lose reciprocity, and the system loses homeostasis. Therefore, both branches of the ANS will get activated randomly and without harmony, which may be the origin of the quick shifts on emotional states, the random confusion and dissociation, and the high level of somatic symptoms.