The active ingredients in marijuana are called Cannabinoids. This is what Wikipedia says about cannabanoids:
Cannabinoids are a class of diverse chemical compounds that act on cannabinoid receptors on cells that repress neurotransmitter release in the brain. These receptor proteins include the endocannabinoids (produced naturally in the body by humans and animals),[1] the phytocannabinoids (found in cannabis and some other plants), and synthetic cannabinoids (manufactured chemically). The most notable cannabinoid is the phytocannabinoid ∆9-tetrahydrocannabinol (THC), the primary psychoactive compound of cannabis.[2][3] Cannabidiol (CBD) is another major constituent of the plant, representing up to 40% in extracts of the plant resin.[4] There are at least 85 different cannabinoids isolated from cannabis, exhibiting varied effects.[5]
There are approximately 60 indentified cannabinoids and each of an infinite number of strains of cannabis has its own cannabinoid profile.
The active cannabinoids each have unique physiological effects and many combinations actually appear to have synergystic and antagonistic effects.
tetrahydrocannabinol (THC):
Euphoric, stimulant, muscle relaxant, , anti-cancer, anti-epileptic, anti-emetic, anti-inflammatory, appetite stimulating, bronchio-dilating, hypotensive, anti-depressant and analgesic effects.
Tetrahydrocannabivarin (THCV, THV), also known as tetrahydrocannabivarol:
A non-psychoactive cannabinoid found naturally in Cannabis sativa. It is an analogue of tetrahydrocannabinol (THC) with the sidechain shortened by two CH2 groups. THCV can be used as a marker compound to differentiate between the consumption of hemp products and synthetic THC (e.g., Marinol). THCV is found in largest quantities in Cannabis sativa subsp. sativa strains. Some varieties that produce propyl cannabinoids in significant amounts, over five percent of total cannabinoids, have been found in plants from South Africa, Nigeria, Afghanistan, India, Pakistan and Nepal with THCV as high as 53.69% of total cannabinoids. They usually have moderate to high levels of both THC and Cannabidiol (CBD) and hence have a complex cannabinoid chemistry representing some of the world’s most exotic cannabis varieties. It has been shown to be a CB1 receptor antagonist, i.e. blocks the effects of THC. In 2007 GW Pharmaceuticals announced that THCV is safe in humans in a clinical trial and it will continue to develop THCV as a potential cannabinoid treatment for type 2 diabetes and related metabolic disorders, similar to the CB1 receptor antagonist rimonabant.
Cannabidiol (CBD):
A major constituent of medical cannabis. CBD represents up to 40% of extracts of the medical cannabis plant. Cannabidiol relieves convulsion, inflammation, anxiety, nausea, and inhibits cancer cell growth. Recent studies have shown cannabidiol to be as effective as atypical antipsychotics in treating schizophrenia. In November 2007 it was reported that CBD reduces growth of aggressive human breast cancer cells in vitro and reduces their invasiveness. It thus represents the first non-toxic exogenous agent that can lead to down-regulation of tumor aggressiveness. It is also a neuroprotective antioxidant. Also lessens the psychoactive effects of THC and has sedative and analgesic effects.
Cannabichromene(CBC):
Promotes the effects of THC and has sedative and analgesic effects.
Cannabigerol (CBG):
Has sedative effects and anti-microbial properties as well as lowering intra-ocular pressure. CBG is the biogenetic precursor of all other cannabinoids.
Cannabinol (CBN):
A mildly psychoactive degradation of THC, it’s primary effects are as an anti-epileptic, and to lower intra-ocular pressure.