Alternatively, elements of both systemic immune disease and OCD may alter physiology so as to perpetuate symptoms of each other; proposed mechanisms involve the stress response, central activity of immunomodulatory signaling molecules such as histamine (Rapanelli et al. 2017), and alterations in microbiota (Sherwin et al. 2016; Rieder et al. 2017). The experience of both acute and chronic medical symptoms such as pain may also precipitate or modify OCD symptoms. There is also growing evidence that chronic psychiatric illnesses affect the expression and severity of immune-related diseases, both in utero (Douros et al. 2017; Van den Bergh et al. 2017) and later in life through altered glucocorticoid and beta-adrenergic activity (Ohno 2017).
