Oxytocin and Immobilization without Fear
The hormone oxytocin plays a key role in social behavior. Oxytocin activates the parasympathetic social engagement system, increasing F1RV (Reyes-Lagos et al. 2019). It is important in pair-bonding, attachment processes, and parental nurturing. The milk ejection reflex in breastfeeding is facilitated by oxytocin, as are labor, sexual arousal, and orgasm. Endogenous oxytocin increases throughout pregnancy, prepares the body for labor, causes uterine contractions, and helps to reduce stress during and after birth (Buckley 2015).
Ordinarily, the dorsal vagal immobilization pathway maintains homeostasis. Yet under perceived threat, immobilization can lead to behavioral shutdown. Oxytocin, often called “the hormone of love,” modifies dorsal vagal function from a fear to a love system. Co-activation of the social engagement and immobilization systems (potentially with a small-to-moderate amount of sympathetic activation) appear central for reproductive behaviors, including sex, birth, and breastfeeding (Porges 2011).
Trust and safety are necessary for immobilization without fear. This state is where we can experience passionate, ecstatic pleasure during sex. When trust and safety are absent from a sexual encounter, pain and tissue damage may occur. Violations of trust switch the context and biology from safety to fear—stimulating sympathetic activation, or switching to immobilized shutdown if flight-or-fight is not an option. As explained above, should both the sympathetic (gas pedal) and immobilization (brake) systems be simultaneously activated, the “freeze” response can occur, as in rape. Oxytocin is thus the differentiating factor between affiliative immobilization without fear and defensive immobilization with fear; as potential threat is detected, the system switches. Porges (2018) describes this in the context of love and sexuality; however, given that these utilize the same autonomic systems as in labor, it seems logical that birth would follow a similar path. Notably, the synthetic oxytocin (Pitocin, or syntocinon) commonly administered in hospitals does not have the same effect as endogenous hormones; rather than supporting labor and breastfeeding, synthetic oxytocin may interfere (Olza-Fernandez et al. 2014; Buckley 2015).