Yes, a Neuropharmocology research study was conducted by Dr. Haney in 2007. Low-dose naltrexone describes the off-label use of the medication naltrexone at low doses for diseases such as multiple sclerosis. Naltrexone belongs to a class of drugs known as opiate antagonists. Opioid antagonists are competitive and bind to the opioid receptors with higher affinity than agonists (drugs eg. Heroin) but do not activate the receptors. This effectively blocks the receptor, preventing the body from responding to opioids. Research study suggests that "marijuana-smoking patients treated with high naltrexone doses may experience an enhanced effect from marijuana. Low doses of naltrexone may decrease marijuana’s effects."
Neuropsychopharmacology (2007) 32, 1391–1403. doi:10.1038/sj.npp.1301243; published online 8 November 2006