Self-harm - The Autonomic Nervous System and Self-Injury

The Autonomic Nervous System and Self-Injury

Everyone has a natural set point for their ability to experience stress. For some people this is a very high threshold whereas other people can become overwhelmed very quickly. Emotional pain activates the same regions of the brain as physical pain so this can be a very intolerable state for some people. Some of this is environmental and some of this is due to physiological differences in responding. One area of interest is the autonomic nervous system, which is composed of two components: the sympathetic nervous system controls arousal and physical activation (i. e. the fight-or-flight response) and the parasympathetic nervous system controls physical processes that are automatic (e. g. saliva production). The sympathetic nervous system innervates (i. e. is physically connected to and regulates) many parts of the body involved in stress responses. For instance, the eyes, heart, and palms are innervated. This is why when we are faced with a stressful stimulus such as a hungry lion or having to give a speech in public our pupils dilate (to take in more information), the heart rate speeds up (to pump blood to muscles needed for fight or flight), and our palms get sweaty. One common measure of sympathetic activity is skin conductance, which measures how sweaty our palms are and how well they conduct electricity. The parasympathetic nervous system controls more automatic processes such as digestion, slowing down heartbeat, and constricting bronchioles in the lungs. When faced with fearful stimuli it is important to be able to reallocate energy from automatic and non-vital processes to the fight-or-flight response. One way to measure an individual’s flexibility to do this is to measure heart rate variability with higher heart rate variability reflecting an ability to deal with stress quickly and efficiently. Studies of adolescents have shown that adolescents who self-injure have greater physiological reactivity (i. e. skin conductance) to stress than adolescent’s who don’t self-injure. Also, it is important to note that this stress response persists over time, staying constant or even increasing in self-injuring adolescents but gradually decreases in adolescents who don’t self-injure.