Cannabis / Marijuana is the most commonly abused illegal drug. It is a derivative of the hemp plant (Cannabis sativa) and can take several physical forms including dried plant material (a green or grey mixture of dried, shredded flowers and leaves), blocks of resin and small containers of Cannabis oil.

Different names for Cannabis include weed, pot, grass, puff, ganja, hash, hashish, herb, skunk, draw and gangster.

Most users roll loose Cannabis into a cigarette called a "joint". It can be smoked in a water pipe, called a "bong", or mixed into food or brewed as tea.

If someone is intoxicated by Cannabis, he or she may have balance problems and have trouble walking. Their eyes may appear red and bloodshot and he or she may exhibit memory difficulties. When the early effects fade, over a few hours, the user can become hungry and later sleepy.

The active ingredient of cannabis (THC or Tetrahydrocannabinol) is detectable using the Drug-Aware Cannabis test kit (THC) for typically 14 to 28 days for frequent use of the drug, or around 5 days for a one-off use, at a cut-off level of 50 ng/ml. The reason for this long retention time is that THC binds with the body's fat reserves - and leaches out over a number of days. You will also undoubtedly have patients who claim that they are positive due to passive smoking. Let us assure you that this is not the case. The cut-off level of the test is set at a level much too high for passive smoking to affect the test results.

People sometimes ask what is the current class of Cannabis? In the UK, the most dangerous or addictive drugs are Class A - such as Heroin, Cocaine and Ecstasy, Class B drugs include Amphetamines and currently

However, this is likely to change in 2009. Cannabis was downgraded from a Class B drug, to a Class C, but this decision looks like it will be reversed due to the potential mental health issues which are manifested in heavy Cannabis users.

Studies have linked heavy Cannabis / Marijuana use to anxiety and mental health disorders such as paranoia, depression, insomnia, schizophrenia and even amotivational syndrome which relates to a lack of ambition or drive.

In order to learn more about drug use (and in particular Cannabis / Marijuana supply and young people), 182 young people who were Cannabis / Marijuana users aged between 11 and 19 years old were interviewed for a study published in January 2008 by the Joseph Rowntree Foundation. The sample included both city dwellers and young people living in rural villages.

The study discovered that half of the young people had taken Cannabis / Marijuana into school or college and 43 per cent admitted that they used Cannabis / Marijuana whilst at school or college. It is clear from the report that the majority of these young people purchase Cannabis from their friends or relatives and in turn supply their friends in a new wave of ?social? and ?not-for-profit? drug taking which is a departure from the typical dealer-user scenario. One young interviewee told the researchers that the people who sold her Cannabis / Marijuana included ?friends from school? and shows how combining drug-use with normal social networking is having the effect of normalising the act of taking drugs.

It has been announced by UK Home Secretary Jacqui Smith that Cannabis will be reclassified as a Class B drug, in order to convey that the drug is harmful and should not be taken.

Cannabis use has dropped, but the reclassification reflects the fact that skunk, a stronger type of Cannabis, now dominates the market. Skunk accounts for 81% of Cannabis / Marijuana available on UK streets compared with 30% in 2002.

Worryingly, the average starting age for Cannabis use is just 13 years old and young people often binge on more potent forms of Cannabis such as skunk, in the same way as alcohol, trying to achieve the maximum effect. If they do, the independent Advisory Council on the Misuse of Drugs found that the consequences of this "may be serious to their mental health".

Taking effect from early 2009, the reclassification will mean:

* More robust enforcement against cannabis supply and possession, and those repeatedly caught with the drug will not just receive cannabis warnings;

* A new strategic and targeted approach to tackling cannabis farms and the organised criminals behind them;

* Introducing additional aggravating sentencing factors for those caught supplying cannabis and other illegal substances near further and higher educational establishments, mental health institutions and prisons;

* Working with the Association of Chief Police Officers to look at how existing legislation and powers can be used to curtail the sale and promotion of cannabis paraphernalia; and

* Updating and refreshing our public information messages on the harm caused by cannabis.

The Home Secretary has asked the Association of Chief Police Officers, working with the Police Federation, the Superintendents Association and Criminal Justice Partners, to propose more robust enforcement measures for policing cannabis as a Class B drug. This will make clear that penalties for adults must be escalated following any cannabis warning and that police officers will not be precluded from arresting for a first offence.

Home Secretary Jacqui Smith said:

"Cannabis is and always has been illegal. It now dominates the illegal drugs market in the UK and is stronger than ever before.

"There is accumulating evidence, reflected in the Advisory Council on the Misuse of Drugs report, showing that the use of stronger cannabis may increase the harm to mental health. Some young people may be 'binge smoking' to achieve maximum possible intoxication which may be very serious to their mental health.

"I make no apology for erring on the side of caution and upgrading its classification. There is a compelling case to act now rather than risk the health of future generations.

"The enforcement response must reflect the danger that the drug poses to individuals, and in turn to communities. Those who are repeatedly caught with Cannabis must face tough punishment and that is why I have asked the Association of Chief Police Officers (ACPO) to propose more robust enforcement measures to reflect re-classification.

"It is also important that the organised criminals behind the growing threat of Cannabis farms feel the full force of the law, and that we use every opportunity and means to disrupt their activities so that the UK becomes a high risk place for them to operate.

"I also want to see more action against the trade in cannabis paraphernalia and will work with ACPO to look at how existing legislation and powers can be used by the police, local authorities and other partners to curtail the sale and promotion of these items."

Health Secretary Alan Johnson said:

"The message has always been that cannabis is a harmful and illegal drug and should not be used. We are determined to ensure that young people in particular are well aware of all the risks. Our multi-media 'FRANK' campaign will ensure that this is the case."

Secretary of State for Children, Schools and Families Ed Balls said:

"Cannabis use by young people has been falling over recent years but remains a persistent problem. The reclassification sends the right message to young people about the risks from Cannabis use - this is especially important given its increased strength and the heightened risk to young people.

"We also know parents are concerned about the recent trend towards the use of stronger strains of Cannabis by young people and the potential for significant mental health problems that would severely impact on a young person's future."