MEDICAL MATTERS: Colorado and Washington have just become the first US states to legalise the possession and sale of cannabis for recreational use. The states, which already have laws legalising cannabis use for medical purposes, are now in conflict with the federal government, which classifies it as an illegal drug.

Preparations of the leaves and resin of the cannabis plant have been in use for over 2,000 years. Short-term effects include a feeling of relaxation and wellbeing. Appetite is often increased and the person appears increasingly talkative.

First introduced into western medicine in the mid-19th century, cannabis was prescribed in the past for a diverse range of complaints including anxiety, arthritis and rheumatic disorders, migraine and painful menstruation. A cannabis derivative, nabilone, is effective in treating nausea and vomiting brought on by chemotherapy treatment in cancer patients. The benefits of cannabis in patients with multiple sclerosis (MS) have been well described. It reduces muscle cramps and relaxes bladder and bowel sphincters.

The medically active cannabis derivative THC reduces the pressure of fluid in the eyeball. Research in the 1970s showed it was effective in the treatment of patients with glaucoma.

Although cannabis is still an illegal substance under the Republic’s Misuse of Drugs Act, a derivative, Sativex, has been recommended for approval by the Irish Medicines Board as a prescription-only medicine. The Government has said it will bring forward legislative proposals either later this year or early next year that will legalise authorised cannabis-based medicinal products while maintaining existing controls on the drug.

Sativex consists of THC and cannabidiol, another cannabis derivative. An oral spray, it improves symptoms in patients with moderate to severe spasticity due to MS.

Hemp, a strong fibre in the stem of the cannabis plant, has been used to make rope and cloth. I recently came across a man who swears hemp oil, taken internally, keeps his arthritic joints mobile. Marijuana proponents argue it is next to impossible to overdose on the drug; they say its lack of addictive properties make it safer than many medicines currently used as muscle relaxants or for pain control.

Cannabis may also be a safer alternative to oral steroids in boosting appetite among cancer and Aids patients.

But cannabis is not without side effects: short-term memory can be impaired, and driving ability and co-ordination are disrupted. Hallucinations may – rarely – occur.

Over the long term, cannabis smoking reduces lung function and increases the risk of lung cancer. It is considered more carcinogenic than cigarette smoke. Regular users may become apathetic and neglect their work and appearance which, it is said, contributed to it falling out of favour with the medical establishment in the early 1900s.

The decrease in concentration produced by cannabis can be dangerous when driving or operating heavy machinery.

Similarly, changes in perception and sense of time could be deadly on the roads.

It seems marijuana also has residual effects on cognitive functioning – including memory – for up to 48 hours after smoking. In susceptible individuals it can precipitate a psychotic episode, and has been linked with the onset of schizophrenia.

But none of these concerns should stop the legislation of medicinal cannabis here. It would bring us into line with practice in the UK, Canada, Italy, Spain and a growing number of US states.

Making cannabis legal under controlled medication legislation should minimise any abuse: people with MS and other debilitating diseases deserve nothing less.