Stress, Hormones, and Eating

Opioid tone may provide a way to identify people at risk of reward based eating, with more accuracy than self-report measures. Knowing such risk could improve treatment matching, and provide a biomarker to assess treatment progress. There is no direct measure of central opioid activity in humans, short of PET scans for opioid receptor binding. However, there is a promising indicator using an opioid antagonist such as naltrexone. Blocking opioid receptor releases the inhibitory opioidergic inputs to hypothalamic corticotropic releasing hormone (CRH) neurons, thus increasing CRH, and eventually cortisol in the blood. The extent of the cortisol rise in response to naltrexone might serve as an indicator of endogenous opioidergic tone. It is hypothesized that greater increases in cortisol indicate weaker endogenous opioid activity (by indicating a more complete opioid blockade). Salivary cortisol response to naltrexone may offer a relatively safe and unobtrusive way to measure endogenous opioidergic tone. We propose to test the reliability and validity of the naltrexone probe, taken at home, as a measure of endogenous opioidergic tone. In a previous study (Daubenmier et al, 2013), we administered a one time 50mg dose of naltrexone and examined nausea and cortisol responses. Results suggested that responses were higher in those who showed greater drive to eat. Here we examine a more direct measure of drive to eat, using the Yale Food Addiction Scale (YFAS), and test whether nausea and cortisol responses were associated with greater drive to eat, whether 50mg produced greater responses than 25 mg, and whether the responses were stable (highly related) when tested again one month later.