Scientists of the Center for Medicinal Cannabis Research (CMCR) of the University of California in San Diego, USA, investigated, among others, the effects of cannabis on appetite hormones in the course of a placebo-controlled trial with HIV patients, who suffered from neuropathic pain. In the original already published clinical study 28 patients had been included to investigate the effects of smoked cannabis on their pain. From these 7 were selected to investigate the blood levels of the hormones leptin, ghrelin, peptide YY and insulin after exposition with cannabis and placebo in a cross-over design. Leptin is known to inhibit appetite, among others by counteracting the effects of the endocannabinoid anandamide. Ghrelin is also considered as a counterpart of leptin. Peptide YY is released in response to feeding and reduces appetite.
Compared to placebo, cannabis administration was associated with significant increases in plasma levels of ghrelin and leptin, and decreases in peptide YY, but did not significantly influence insulin levels. Authors stated that "cannabis-related changes in these hormones had a magnitude similar to what has been observed with food intake over the course of a day in normal volunteers, suggesting physiological relevance." They concluded that "these findings are consistent with modulation of appetite hormones mediated through endogenous cannabinoid receptors, independent of glucose metabolism."