Cannabis is the most widely-used illegal drug in Britain.
What is Cannabis
Cannabis is also known as marijuana, and refers to products of the dried leaves, flowers, stems, and seeds of the hemp plant, Cannabis sativa.
The plant contains the chemical delta-9-tetrahydrocannabinol (THC) which is responsible for generating the high feeling.
Cannabis is known as Grass, Weed, Council, Reefer, Dope, Ganjha, Skunk, Pot, Resin, Hash, and Solid.
It is categorised as a depressant, hallucinogen, and stimulant.
What does it look like?
Although it's all from the same plant, cannabis comes in different forms.
Hash is a black or brown soft lump made from the resin of the cannabis plant. It's much less common in the UK than it used to be.
Grass, or weed, is made from the dried leaves and flowering parts of the female cannabis plant and looks like tightly packed dried herbs. This traditional form of cannabis is usually grown in the UK.
Skunk is a cannabis bred to produce much higher concentrations of THC. Sinsemilla and netherweed are names of two varieties of skunk. Skunk is much stronger than traditional weed.
Cannabis oil is a sticky, dark honey-coloured substance and not common.
How it is taken?
Most people smoke cannabis in hand-rolled cigarettes mixed with tobacco known as spliffs or joints. It can also be smoked in pipes or water pipes known as bongs, or in emptied cigars, partly or completely refilled with cannabis, known as blunts.
To avoid inhaling smoke, more people are using vaporizers. These devices pull the active ingredients from the cannabis and collect the vapour in a storage unit. A person then inhales the vapour, not the smoke.
Some people mix cannabis in food such as cakes, biscuits, or sweets, or even brew it as a tea. Edibles take longer to have an effect.
A growing method of use is smoking or eating different forms of THC-rich resins extracted from the plant and referred to as dabbing.
Popular forms of the resins are:
These resins can deliver extremely large amounts of THC to users, and their use has sent some people to the emergency room.
Preparing these resins usually involves butane (lighter fluid). Many people who have used butane to make the resins have caused fires and explosions, and some have been seriously burned.
What are the effects
Cannabis can provide a genuine feeling of calm, relaxation, and pleasure with a sharper sense of colours and sounds. In addition, there is also growing evidence that it can provide relief for chronic pain where many other medications do not work.
Cannabis can have a number of negative side effects both short and long term. Some will disappear as soon as cannabis smoking stops, and some will persist for years afterwards.
When smoking cannabis, people can become hungry, referred to as 'getting the munchies', harmless except to one's waistline. By contrast, some people have one or two drags on a joint and feel light-headed, faint and sick, called a 'whitey'.
Regular use can reduce concentration, memory and motivation. This is particularly serious for young people whose brains are still developing, and still in education.
More serious possible effects of cannabis, include anxiety, suspicion, panic and paranoia, even hallucinations. These symptoms often abate when smoking stops.
Probably the most serious side effect of cannabis, is that some people develop serious, long-term mental health problems like schizophrenia. People with a family history of psychotic illnesses are particularly vulnerable, while those with a personal history are susceptible to a relapse or their condition worsening.
Cannabis can increase heart rate and affect blood pressure, which can be dangerous for people with heart disease.
Tobacco and cannabis share some of the same chemicals, so smoking cannabis can make asthma worse, cause wheezing and lead to lung cancer. Also, mixing cannabis with tobacco introduces all the risks associated with smoking tobacco, ranging from coughs and chest infections to cancer or heart disease.
A review of cannabis in the British Medical Journal found those driving under the influence of cannabis had nearly double the risk of a crash. Mixing cannabis with alcohol can have particularly serious consequences - the accident rate is 16 times higher than for cannabis or alcohol alone.
When a person smokes cannabis, THC quickly passes from the lungs into the bloodstream. The blood carries the chemical to the brain and other organs throughout the body very quickly so the effects are felt quickly.
By contrast, the body absorbs THC more slowly when the person eats or drinks it, and the user generally feels the effects after 30 minutes to 1 hour. If taken in food, effects can be stronger and harder to control.
Is cannabis a gateway drug?
There are strong opinions on the subject of cannabis being a gateway drug. While some research suggests that cannabis users may go on to harder drugs, the vast majority of people do not do so according to surveys.
In the UK, Cannabis is a Class B drug; illegal to have, give away or sell. Possession can result in up to five years in prison, an unlimited fine, or both. Supplying people, including friends, can result in up to 14 years in prison and/or an unlimited fine.
The trend in the West appears to be towards the legalisation of Cannabis for medical and personal, which many argue is less harmful than legal drugs like alcohol. UK MPs have urged the government to leglise Cannabis in the UK.
The President of Colombia, Juan Manuel Santos, has used his Nobel Peace Prize acceptance speech to call for the world to "rethink" the war on drugs.
He said the zero-tolerance policy might be "even more harmful" than all the other wars being fought worldwide.Drugs workers fear a "bad batch of heroin" could have led to the deaths of at least seven drug users in recent weeks in the Gwent Police force area.
Drugs workers fear a "bad batch of heroin" could have led to the deaths of at least seven drug users in recent weeks in the Gwent Police force area.
According to NHS figures, 1,087 babies in England were affected by maternal use of drugs in 2014-15, while in Scotland 987 babies were affected.
The Metropolitan Police has said it will examine 58 GHB-related deaths, following the conviction of serial killer Stephen Port.
A leading police chief says recreational drug testing "may be very useful". Commander Bray is in discussion with the government about it.
Britain should follow America's lead and legalise cannabis, and rake in £1 billion a year in tax revenues
Marijuana legalization will unleash misery on Arizona, according to a wave of television ads that started rolling out across the state last month.
Police in Denmark have arrested a man and woman on suspicion of providing cannabis to cancer patients and people with other serious illnesses.
The National Drugs Helpline is a 24-hour, 7-days a week, free and confidential telephone service that offers advice and information for anyone.
It is run by the government agency, known as FRANK, created to provide drug support and advice for the public.
If you need emergency help, are worried about a friend or relative's drug use or want support coping with your own, contact FRANK on-line contact or by phone.
Canada has laid out its plan to legalise the sale of recreational marijuana by June 2018. If it passes, the country will be the largest developed nation to end marijuana prohibition.
The law was tabled on Thursday, and would allow adults over 18 to possess up to 30g of dried marijuana. However, it has been a slow process to put the law into practice
Uruguay will begin selling cannabis in pharmacies from July, the final stage in the country's pioneering regularisation of the drug.
The South American country will be the first in the world to legally sell the drug over the counter for recreational use.
The move started in 2013 with a law that fully legalised the cannabis trade.
From the first-floor window of the flat where he was incarcerated, 15-year-old Tung began to piece together what the UK was like. He liked watching the busy road with three or four shops, a pizza restaurant and a petrol station. He had been told never to turn on the light, so he often sat by the window in the dark, peering out from the side. "Where I lived in Vietnam was a very remote area, just trees and dirt tracks. We rarely saw a car. I found it all so surprising."
As marijuana legalization swept the US in November, Arizona was alone in its rejection of legal weed. There, a pharmaceutical company called Insys was a major backer of the successful campaign to stop the state's recreational cannabis measure, publicly arguing that pot businesses would be bad for public health and endanger children.
But to marijuana activists, the motive was clear - to squash the competition.
Chemicals found in cannabis could be used to help treat dementia, early studies have shown - but further research into the findings is being stymied by restrictive drug laws, scientists say.
Cannabinoids like tetrahydrocannabinol (THC) can aid the removal of dangerous dementia proteins from brain cells, according to researchers at the Salk Institute, a renowned biomedical research facility in California.
Scientists are calling for a major effort to make cannabis use less harmful as a rising number of countries look to replace long-standing and outright bans on the drug with more relaxed legislation.
A number of countries and US states have softened laws around cannabis use against a backdrop of rising drug potency and an apparent increase in the number of people in treatment for cannabis-related problems.
Clever children are twice as likely to smoke cannabis during their teenage years due to their curious minds, a landmark study has revealed.
Students who are high academic achievers at the age of 11 are also more likely to drink alcohol as teenagers, but less likely to smoke tobacco cigarettes, a nine-year study by University College London found.
Cannabis has long been associated with hippies and students. But as marijuana is gradually legalised across the US and other parts of the world, growers and sellers are looking to change its image and attract new clients.
Enter Olivia Mannix, the founder and CEO of Cannabrand: what is believed to be the first marketing agency dedicated to cannabis.
The legalisation of marijuana in several US states has not curbed beer sales, according to new research, as Americans managed to find room in their social schedules for both.
Analysts at investment firm Bernstein said fears that the brewing industry would be sent into chronic decline by red-eyed revellers reaching for joints instead of beers have proved unfounded.
There is not enough research to reach conclusive judgments on whether marijuana can effectively treat most of the symptoms and diseases it is advertised as helping, according to a wide-ranging US government study.
The same is also true of many of the risks said to be associated with using cannabis, the study finds.
The cannabis market in Australia is estimated to be bigger than the wine market. But unlike our wine market, not a cent of Australia's cannabis is taxed.
In 2014-15, 66,309 people were arrested in Australia for possessing cannabis. The number of people arrested for cannabis consumer offences increased more than 40% between 2004-5 and 2014-15. No one knows what it costs to police and process cannabis possession.
An unprecedented number of older people are using illegal recreational drugs in the US, according to a study which has revealed a 70 per cent spike in cannabis use among Baby Boomers in the past decade.
"For years we've been worried about the potential effects of marijuana on the developing brains of teens, but now we may need a bit more focus on their grandparents," said Dr Joseph J. Palamar of New York University.
Cannabis should be legalised in the UK, according to a report that has the backing of several cross-party MPs.
Current cannabis policy in Britain is a "messy patchwork" of legislation, says the report by the free-market thinktank the Adam Smith Institute. The government must recognise that legalising the Class B drug is the "only workable solution to the problems of crime and addiction in the UK.
Faced with stark numbers of brain trauma and psychological distress cases among combat veterans, the nation's largest active veteran's organization is pushing for relaxing federal restrictions on marijuana.
The American Legion took a position on medical marijuana for the first time. At its convention, it passed a resolution calling on Congress to amend its laws to "at a minimum ... recognize cannabis as a drug with potential medical value".
One of the biggest detractors from legalization is the public sentiment that it will lead to easier teen access to cannabis. A new study on Washington State has shown that that will not be the case. In fact, not only does it not make cannabis easier to get, it makes hard drugs harder.
The study presented at the Pediatric Societies 2016 meeting on 1 May shows that there is virtually no change in teen perception on access to cannabis.
It's been a year since Colorado became the first state in the US to legalise marijuana, and its impact on health, crime, employment and other factors can now be more empirically measured.
So, did it bring about an apocalypse as some feared? "We found there hasn't been much of a change of anything," a Denver police officer told CBC. "Basically, officers aren't seeing much of a change in how they do police work."
Cannabis is still the most widely used substance in the UK, even thoughthere has been a steady reduction in use since 1996.
In spite of warnings, many people see cannabis as a safe substance that helps you to relax. Research over the last 10 years has suggested that it can have serious consequences for people, such as the development of an enduring psychotic illness, particularly in those who are genetically vulnerable.
The teenager's brain must transform from the brain of a child into the brain of an adult. Some researchers worry how marijuana might affect the process.
"Actually, in childhood our brain is larger," says Krista Lisdahl, director of the brain imaging and neuropsychology lab at University of Wisconsin, Milwaukee. "Then, during the teenage years, our brain is getting rid of those connections that weren't really used, and it prunes back.
A former government adviser has told MPs that alcohol consumption would fall by as much as 25% if Dutch-style cannabis "coffee shops" were introduced.
Prof David Nutt also told the Commons home affairs committee that he stood by his claim that horse-riding was more dangerous than taking ecstasy, despite the fact that the comparison triggered his sacking as chairman of the advisory committee on the misuse of drugs.