Preparations of the leaves and resin of the cannabis plant have been in use for over 2,000 years.
First introduced into Western medicine in the mid-19th century, cannabis was prescribed in the past for a diverse range of complaints including anxiety, rheumatic disorders, migraine and painful menstruation.
The short-term effects of cannabis include a feeling of relaxation and well-being. Appetite is usually increased and the person appears increasingly talkative.
However, short-term memory can be impaired, and driving ability and co-ordination are also disrupted. Hallucinations may rarely occur.
Over the long term, cannabis smoking increases the risk of lung cancer. It is considered more carcinogenic than cigarette smoke.
Regular users may become apathetic and neglect their work and personal appearance. In susceptible individuals the drug can precipitate psychosis, and has been linked with the onset of schizophrenia.
A cannabis derivative, nabilone, is successfully used to treat nausea and vomiting brought on by chemotherapy treatment in cancer patients.
The benefits of cannabis in patients with multiple sclerosis have been described; it reduces muscle cramps and relaxes bladder and bowel sphincters. The cannabis derivative THC reduces the pressure of fluid in the eyeball and could be used to help patients with glaucoma.
The reclassification of cannabis in the United Kingdom has stimulated renewed debate as to its legal status in the Republic.
In the UK cannabis has been reclassified as a class C rather than a class B drug, putting it in the same category as steroids and benzodiazepines.