Marihuana has been used for thousands of years. The bark of the plant is especially useful for making a type of rope called hemp and marihuana is sometimes called the hemp plant. In some countries (e.g., Japan), marihuana is still grown for its hemp. In the United States colonial times, George Washington was known to cultivate marihuana for hemp! Some “counterculture” shops in the United States and elsewhere sell clothing that is woven out of hemp. The THC content of marihuana varies regionally. In some low-grade plants it is less than 1%. With careful breeding and cultivation and removal of male plants a form of female, seedless marihuana called sinsemilla, can be grown with THC content as high as 10%. There is also a Federal Government that supported experimental farm in Mississippi, where marihuana with THC content over 30% has been cultivated. The THC in marihuana is concentrated in the resin, which is most abundant in the flowering tops and leaves of the plant. The stalks, seeds, and roots contain almost no THC and are generally removed. The leaves and flowers are dried and then smoked. In many jurisdictions, marihuana stems and stalks are not controlled and seeds are only controlled if they are viable (they can be germinated). Concentrated forms of marihuana are prepared in various ways and known by different names all over the world. In the United States, the plant material can be boiled in methyl alcohol, filtered, and then evaporated down to a thick, gooey liquid known as hashish (hash) oil. High quality hash oil may contain more than 50% THC. Another preparation, hashish (hash) is prepared by collecting the resin from the live plants with leather straps and cloths. It consists of resin and hairs from the plant. It is a solid and is often sold in bricks. Hash oil and hash are generally smoked in small pipes that are designed for this purpose. The dish in the center of Figure 13.9 shows some pieces of hashish.

The side effects and risks involved with consuming marijuana-based products aren't clear, either, Bonn-Miller said. It's important to "determine cannabinoids that are useful therapeutically while understanding and using cannabinoids that are associated with less risk," he said. At least with CBD, he said, it doesn't appear to have the potential for addiction. That's different from THC, which has been associated with addiction, he said, and negative side effects, including acute anxiety.
Collin, C., Ehler, E., Waberzinek, G., Alsindi, Z., Davies, P., Powell, K., Notcutt, W., O'Leary, C., Ratcliffe, S., Novakova, I., Zapletalova, O., Pikova, J., and Ambler, Z. A double-blind, randomized, placebo-controlled, parallel-group study of Sativex, in subjects with symptoms of spasticity due to multiple sclerosis. Neurol.Res. 2010;32(5):451-459. View abstract.
As of November 2016, 33 states and the District of Columbia legally allow cannabis for personal medical use. Rules surrounding the use of medical cannabis (medical marijuana) vary by state. The first state in the union to legalize the medical use of marijuana was California in 1996. States that allow medical marijuana include: Alaska, Arizona, Arkansas, California, Colorado, Connecticut, Delaware, Florida, Hawaii, Illinois, Maine, Maryland, Massachusetts, Michigan, Minnesota, Missouri, Montana, Nevada, New Hampshire, New Jersey, New Mexico, North Dakota, New York, Ohio, Oregon, Pennsylvania, Rhode Island, Utah, Vermont, Washington, and the District of Columbia. It is important to recognize that these state marijuana laws do not change the fact that using marijuana continues to be an offense under Federal law.
Carbon dioxide is passed through the plant material at a very specific temperature and pressure. Carbon dioxide, which is normally a gas at (or above) room temperature, can be pressurized until it becomes so dense that it takes on some of the properties of a liquid while still maintaining the fluid dynamics of a gas. In this state, CO2 is known as a supercritical fluid.
^ Jump up to: a b Batalla A, Bhattacharyya S, Yücel M, Fusar-Poli P, Crippa JA, Nogué S, Torrens M, Pujol J, Farré M, Martin-Santos R (2013). "Structural and functional imaging studies in chronic cannabis users: a systematic review of adolescent and adult findings". PLOS One. 8 (2): e55821. Bibcode:2013PLoSO...855821B. doi:10.1371/journal.pone.0055821. PMC 3563634. PMID 23390554. The most consistently reported brain alteration was reduced hippocampal volume which was shown to persist even after several months of abstinence in one study and also to be related to the amount of cannabis use Other frequently reported morphological brain alterations related to chronic cannabis use were reported in the amygdala the cerebellum and the frontal cortex...These findings may be interpreted as reflecting neuroadaptation, perhaps indicating the recruitment of additional regions as a compensatory mechanism to maintain normal cognitive performance in response to chronic cannabis exposure, particularly within the prefrontal cortex area.
The AKC Canine Health Foundation (CHF) is currently sponsoring a study, through the Colorado State University’s College of Veterinary Medicine and Biomedical Sciences, that will evaluate the use of CBD in treatment-resistant epileptic dogs. The CHF hopes that this will be the first study to gain scientific data on the use of CBD in dogs with this condition.

CBD Sleep