By Lorna Duckworth, Social Affairs Correspondent Source: Independent More adults use cannabis in Britain than in any other European state and almost half of the nation's teenagers are thought to have smoked the drug by the time they leave school. But the debate over the health impact of cannabis is highly controversial, with supporters of the drug claiming it has few harmful effects and opponents warning it can do serious damage. The adverse effects for regular users, and the medicinal benefits for patients with chronic conditions such as multiple sclerosis, are still not fully proved, partly because the drug has more than 400 active ingredients. Cannabis users take the drug because of its mildly sedative effect, which leads to lower blood pressure, increased appetite, feelings of relaxation and increased sociability. But if cannabis is smoked, people have all the long-term risks of tobacco such as mouth and lung cancers, bronchitis and increased risk of heart attacks. In some first-time users it can provoke anxiety, panic and suspicion. There is also evidence that, in extreme cases, it can produce severe mental disturbance, and precipitate or aggravate schizophrenic attacks. Long-term side-effects include distorted perception, slower reaction times, impaired co-ordination and driving skills, and lack of motivation. Some research has suggested that heavy users can suffer acute mental problems, loss of control, irrational fears and depersonalisation. Concerns have also been raised that plant breeding has made the drug many times more potent than it was in the 1960s. Some people argue cannabis can lead to use of hard drugs such as heroin, but this is not true for most users. Dr Claire Gerada, a specialist in drugs, said: "Cannabis is undoubtedly safer than heroin or cocaine. But if the constraints are relaxed, I would be concerned about increased use of the drug and more problems with side-effects as people use it for longer." Evidence that cannabis has a medicinal benefit led the House of Lords Science and Technology Committee to recommend in 1998 that it should be used for therapeutic purposes. But the Government is awaiting the results of clinical trials before deciding whether cannabis extracts should be prescribed to patients with multiple sclerosis, to help ease their muscle spasms and tremors, or to reduce the side-effects of chemotherapy in cancer patients. America's Food and Drug Administration has approved the oral use of dronabinol, a cannabis derivative, for people with Aids. Cannabis analogues have been shown to prevent seizures in epileptic patients when given in combination with prescription drugs. Claims have also been made for the drug's use in treating asthma, strokes, Parkinson's disease, Alzheimer's disease, alcoholism, insomnia and glaucoma. Complete Title: Scientists Still at Odds Over Risks and Benefits of Taking Cannabis Related Article: A Cause That Unites Across The Spectrum Author: Chris Gray Published: June 25, 2001 Support for liberalisation of the cannabis laws reaches across the political spectrum, from Tory libertarians to left-wing Labour MPs and Trotskyite Scottish socialists. It has been crystallised by a Police Foundation report into Britain's drugs laws, which last year suggested the scrapping of jail sentences for possessing the drug. The inquiry, chaired by Viscountess Runciman of Doxford  a well-known champion of health causes linked with social exclusion  argued that criminal penalties for cannabis possession were more harmful than the drug itself. Its main recommendations were rejected by Jack Straw when he was Home Secretary, but Lady Runciman, a former member of the Government's Advisory Council on Misuse of Drugs, insisted its "time would come". Clare Short has called for a fresh look at the problem while liberalisation, and in some cases full decriminalisation, has the support of several other left-wing Labour MPs including Tony Banks, Paul Flynn and Lynne Jones. They are joined by Tommy Sheridan, the far-left leader of the Scottish Socialist Party. Right-wing libertarian Conservatives have publicly made the same case. Last week, five Tories  including the MEP and former health minister John Bowis  announced their support for liberalisation and called for their party to look long and hard at changing its policy on drugs. The Liberal Democrats have traditionally been most in favour of decriminalisation. When Charles Kennedy took over he called for a Royal Commission on the issue, and has said that he is personally in favour of decriminalisation. Source: Independent (UK) Author: Lorna Duckworth, Social Affairs Correspondent Published: June 25, 2001 Copyright: 2001 Independent Newspapers (UK) Ltd. Website: http://www.independent.co.uk/ Contact: letters@independent.co.uk