The Journal of the American Medical Association (JAMA) published:
Medical Cannabis Laws and Opioid Analgesic Overdose Mortality in the United States (1999-2010)

Here is a link to a study done by John Hopkins University and the Philadelphia Veterans Affairs Medical Center:
Prescription drugs overdose deaths lower in states with legal medical marijuana

The above results are due to the fact that Cannabis amplifies the pain blocking effect of opioids, aspirin, and ibuprofen. Therefore, a smaller quantity of the opioid, aspirin or ibuprofen can be used, if combined with cannabis, to block the same amount of pain.

PHARMACEUTICAL COMPOSITION FOR THE TREATMENT OF CHRONIC OBSTRUCTIVE PULMONARY DISEASE.

TREATING OR PREVENTING DIABETES WITH CANNABIDIOL

COMBINATION OF CANNABINOIDS FOR THE TREATMENT OF PERIPHERAL NEUROPHATIC PAIN.

ANTI-NAUSEA AND ANTI-VOMITING ACTIVITY OF CANNABIDIOL COMPOUNDS

PROSTATE CANCER RESEARCH.

ENDOCRINOLOGY RESEARCH INTO BREAST AND PROSTATE CANCER.

On "SCIENTIFIC AMERICAN" Volme 291 Number 6 (Dec. 2004) there is an article on page 68 named "The Brain's Own Marijuana". The article is about the endocannabinoids, cannabinoids produce by our body (such as Anandamide), and how these cannabinoids play an important role in controlling brain activity.

There is a new documentary named "Weed The People" in Netflix that shows the results of two recent medical studies. In one studies, we can see how cancer cell commit  apoptosis (cancer cells kill themselves) when they come in contact with Cannabigerol (CBG). In the other study, tumors in rats are significantly shrunk when CBG is added to their diet.

In fact, as far back as 1996 ( 1996 medical study ) it was known that CBG has antitumor properties. CBGA (Acidic CBG) is a precursor to CBDA, CBCA, & THCA. And CBG does not make us high. The hemp plants, that are now legal, have a high concentration of CBG, but almost no THC. And the medical marijuana that has high THC content have very low CBG content.

Endogenous Cannabinoid System.

Cannabis Compounds Reduce Multi-Drug Resistant Infections

Cannabis May Help Combat Cancer-causing Herpes Viruses