Exploring dissociation and oxytocin as pathways between trauma exposure and trauma-related hyperemesis gravidarum: a test-of-concept pilot.

Posttraumatic stress disorder (PTSD) is associated with gastrointestinal and genitourinary comorbidities. These map onto the somatization disorder symptoms in the Diagnostic and Statistical Manual of Mental Disorders ( American Psychiatric Association, 1994 ) and the dissociative (conversion) disorders symptoms in the International Classification of Diseases taxonomy ( World Health Organization, 2007 ). Hyperemesis gravidarum (HG) is one of these symptoms and a gastrointestinal comorbidity of PTSD occurring in pregnancy. It is an idiopathic condition defined as severe vomiting with dehydration, metabolic imbalance, wasting, and hospital care seeking. HG is more severe than the normative phenomenon of nausea and vomiting of pregnancy. This test-of-concept pilot (N = 25) explored the hypothesis that there is a trauma-related subtype of HG characterized by (a) high levels of dissociative symptoms and (b) altered plasma concentrations of oxytocin. This hypothesis is informed by a theory of posttraumatic oxytocin dysregulation that posits altered oxytocin function as a mechanism of gut smooth muscle peristalsis dysfunction. A 4-group analysis compared controls with nausea and vomiting of pregnancy (NV only) and cases with HG only, NV and PTSD, or HG and PTSD. Oxytocin was correlated with the nausea and vomiting symptom severity score (r = .464, p = .019) and with the dissociation symptom score (r = .570, p = .003). Women in the group with both PTSD and HG (the trauma-related HG subtype) had the highest levels of dissociation and the highest levels of oxytocin. A linear regression model indicated that the independent association of the trauma-related HG subtype with oxytocin level was mediated by high levels of dissociative symptoms.