Cannabidiol (CBD) is one of the 150+ naturally occurring phytocannabinoids found in certain strains of hemp and in all cannabis plant strains.

It is legal in many places and is used in the management and treatment of chronic pain, PTSD, anxiety, anxiety disorder, depression, diabetes type 1, diabetes type 2, seizures, and in conjunction with allopathic approaches to diseases including cancer chemotherapy and radiation therapy. Anecdotally CBD is being used with claimed positive results by patients for almost every illness.

Legal 
CBD, unlike Δ9-THC (Tetrahydrocannabinol), is a non psycho-active compound of cannabis. Its use and popularity as an alternative to pharmaceutical drugs is growing worldwide despite difficulties, ambiguities and, in some cases, contradictory legal status in some states and countries.

In the USA the consumption of CBD hemp oil is federally legal, since CBD hemp oil falls under the same importation and commerce laws as other hemp products. Some US states have not enacted legislation specifically relating to CBD hemp oil and continue to use high THC cannabis laws to govern the status of CBD. At the same time many states have legislated to legalize or decriminalize cannabis.

Most states have detailed information relating to the legal status of recreational cannabis, CBD, and what is increasingly referred to as 'medicinal cannabis'. up-to-date state specific info can be seen at Legal history of cannabis in the United States (in Notes).

In 1939 Irishman William Brooke O'Shaughnessy introduced cannabis extract to American pharmacies and thus began it's popularity as a remedy. A wide range of cannabis extracts became freely available and could be gotten from travelling doctors, 'snake oil salesmen', and apothecaries across America and Europe.

The general lack of controls and regulation at the time lead to some deaths and injuries linked back to supposed cannabis extracts. Unscrupulous makers produced formulations that were of questionable quality for quick profits and some cases the ingredients were toxic or poisonous. This unfortunate practice was widespread across the profitable field of medicine and remedies.

As result, in 1906, The Pure Food and Drug Act was passed by the United States Congress. It required that certain special drugs, including cannabis extracts, be properly and correctly labeled with contents. Prior to this many drugs were marketed as 'patented' medicines with 'secret ingredients'. The new regulations, however, did nothing to stem criticism about the availability of narcotics in particular and around 1910 there was a new round of legislation aimed to strengthen requirements for their sale and remove 'loopholes' in poison laws.

The 1910 revisions were designed to restrict all narcotics, including cannabis, as poisons therefore requiring a doctors prescription and limiting sales to pharmacies only. The first instance of the 1906 Act was enacted by the District of Columbia in the same year as 'An act to regulate the practice of pharmacy and the sale of poisons in the District of Columbia, and for other purposes'. The act was again updated in 1938 to the Federal Pure Food, Drug, and Cosmetics Act of 1938 which is still current as of the early 21st century. To date, marijuana remains under this law defined as a "dangerous drug".

CBD as a separate substance or as an ingredient of other products is legal across the USA since it is a hemp extract however when purchasing people should check their specific local and national laws.

History 

Evidence suggests that hemp and cannabis may have been farmed for up to 12,000 years and had many uses including the making of cloth, rope, paper, food, and medicine. However, in the modern context, it was not until its introduction to American pharmacies by William Brooke O'Shaughnessy in 1839 that Cannabis extracts came into mainstream awareness as a medicine. A wide range of cannabis extracts became easily available and could be gotten from travelling doctors and salesmen, doctors, and drugstores throughout America. This ended the introduction of the Pure Food and Drug Act. Similar products were also available across Europe.

Uses of CBD 
In the early decades of the 21st century, CBD is again becoming well known for its qualities as a remedy for health problems. Its world-wide popularity is ahead of the slow process of making it legal to produce, supply, buy, and use cannabis for enjoyment in non-medical settings, and especially when it comes to CBD, which doesn't have a psycho-active component.

There is some experience that CBD has a positive effect in managing and treating chronic pain, PTSD, anxiety, anxiety disorder, depression, diabetes type 1, diabetes type 2, seizures, and also combined with allopathic approaches to diseases including chemotherapy and radiation therapy for treating cancer. No toxic dose for CBD is known, and there is no record from any source of a death or serious injury from CBD as of this writing.

CBD may be useful either as treatment for a specific illness or in a smaller dose for maintenance of good health. Usually, CBD is taken by mouth as oil drops or a powder that dissolves in water, or made into a food to be eaten. Another form of CBD is used on the skin as the oil or a cream to rub in. CBD is popularly taken in the 'vape' method (from the word "vapor"), with the CBD is heated so it can be inhaled. This method is favoured because the effect is felt sooner than by other means. Patients who need long-lasting relief from pain or other symptoms such as nausea, may combine two methods: for example, first vape and then eat a food made with CBD.

References 

Cannabis
Organic compounds
Pharmacology