Calls for more research into the medicinal use of cannabis were made at the annual convention of the American Association for the Advancement of Science (AAAS) held in California last week.

Proponents of the use of cannabidiol (CBD), an active component of cannabis, claim it could help patients suffering from a wide range of medical conditions, such as chronic pain , epilepsy and anxiety-related psychological disorders. It has also been suggested that CBD could even help treat those addicted to new varieties of super-strength cannabis known as 'skunk'.

Financial concerns for investment are one of the main reasons suggested for multi-national pharmaceutical companies being reticent to get involved in cannabis research. In an interview for the Royal Society of Chemistry, Mark Ware, leader of the pain research unit at McGill University, Canada, explained: "They are old drugs. They are hard to lock in patents and that makes it difficult for someone to invest significantly into these kinds of research studies that might not have the long-term payback."

The illegal status of cannabis in most US states and in the UK means that permission for research needs to be sought, adding further complications for universities and other research establishments.

One of the more surprising medical applications of CBD is in the treatment of addiction to very high strength 'skunk' cannabis. Skunk contains up to four times more of the other main active ingredient, tetrahydrocannabinol (THC), which has been widely associated with cannabis-related psychosis and memory loss. In an interview for the BBC - whose Radio 4 flagship news programme, Today, recently devoted a week-long series of features to the drug -  Professor Val Curren of University College London described the THC/CBD effects as being like a 'yin/yang' relationship, with CBD mitigating the negative effects of THC.

"The THC makes you stoned, but it can also make you anxious. It can also make you feel a bit psychotic, and will seriously impair your memory. The other side of the yin/yang is CBD, which has almost the opposite effects. CBD calms you down, it has anti-psychotic properties and it also offsets the effects on memory," she explained.

In 1999, the House of Lords in the UK recommended that cannabis be made available for medical use by prescription from doctors, but the then government rejected the findings, though more detailed clinical trials were allowed. In 2003, GW Pharmaceuticals were given a licence to produce a medical cannabis derivative, branded as Sativex, though this was not passed for prescribing until 2013. Its prohibitive high cost, however, has made its use in the UK infrequent and not cost effective compared to US produced alternatives.

The AAAS's calls last week and the added profile in the UK from the Today programme will only fuel more calls for continued research and implementation of cannabis for medicinal use.