ABSTRACT
Neurobiological studies of NSSI point to abnormalities on the hypothalamic-pituitary-adrenal (HPA) axis, in the endogenous opioid system and in the neural processing of emotionally, socially or physically adverse stimuli. Intensely stressful experiences during childhood may permanently influence stress responses and stress management later in life. Exposure to stress activates the autonomic nervous system and the HPA axis. The former system releases the hormones adrenalin and noradrenalin, which activate the sympathetic part of the autonomic nervous system, putting the body on alert and mobilizing energy for flight or fight. The other systemic stress response is the release of cortisol from the adrenal cortex under influence from the HPA axis. Studies suggest that persons with emotional dysregulation and NSSI have a more sensitive and active amygdala response, which offers a physiological explanation of their tendency to be more impulsive, sensitive, reactive and tense. This heightened stress response means that persons with NSSI need an increased level of endogenous opioids to regulate inner tension, which helps explain why NSSI can have an instantly calming effect. Studies have found a connection between reduced serotonin levels and increased impulsivity, aggression, suicide attempts and NSSI. The chapter also briefly outlines the role of serotonin in NSSI.
