Even short term use of cannabis can damage the lungs of young people, say researchers.
A team from Queen Elizabeth Hospital, Birmingham, conducted tests on smokers, non-smokers and cannabis users. Non-smokers had the healthiest lungs. But cannabis users showed more signs of damage than those who stuck to cigarettes. A British Thoracic Society meeting heard less than six years cannabis use was enough to cause significant damage.
Dr Sarah Nuttall, a research fellow from the Department of Clinical Pharmacology at Queen Elizabeth Hospital, said: “The consensus among many  young people who use cannabis seems to be that they will not suffer any long-term effects as long as they stop smoking it early enough “However this is clearly not the case – our study shows that even short-term use of cannabis in addition to tobacco use does have an impact and makes a serious difference to lung function.”
Dr John Harvey, chairman of the BTS communications committee, said: “It is vital that young people understand the dangers of both cigarette and cannabis smoking since these habits can start having a serious impact on their lungs at an early stage.”
A British Medical Journal study published earlier this year warned that regular cannabis use may be as dangerous as smoking in the long term.
Professor John Henry, a toxicologist at Imperial College London, feared that deaths attributable to cannabis could soar.
There are currently an estimated 3.2 million people in the Britain who smoke cannabis regularly, compared with 13 million tobacco smokers.

In a recent double-blind, placebo-controlled study, using both smoked marijuana and THC infusions, Mathew et al studied the effect of tetrahydrocannabinol (THC) on blood pressure, pulse rate and blood flow to the brain to determine the extent of the phenomenon of dizziness or faiting associated with blood pressure drop when standing up after smoking a joint. A blood pressure drop that results in fainting ‘has considerable clinical relevance. In healthy individuals, it can cause injuries including lacerations and fractures. In individuals with pre-existing cerebrovascular disorders it can lead to stroke and sudden death’. Further it complicates a variety of diseases including multiple sclerosis, diabetes mellitus, Shy Drager syndrome, nephrosis, chronic fatigue syndrome, Parkinsonism, organic dementia and cervical myelopathy’. In ‘elderly ambulatory men’ it was found to be a significant and independent predictor of mortality. 28% of those studied reported severe symptoms, both with smoked marijuana and the THC infusions. The study found that the most marked autonomic change caused by marijuana was increased pulse rate. ‘ The results of the study clearly show loss of cerebral autoregulation and postural syncope (fainting when standing up) after ingestion of marijuana/THC. However the mechanism responsible for these phenomena is unclear.

Note: the 29 subjects were all experienced marijuana smokers. The study was reviewed and approved by the Institution Review Board (IRB) at Duke University Medical Center.
Source: A transcranial Doppler study of the hemodynamics. R J. Mathew et al Pharmacology:
Biochemistry and Behavior 75 (2003) 309-318

Cannabis dependence assessed at age 18 and 21 increased from 6.6% for 18 to 9.6% at 21. unemployment or violent behavior more frequent with cannabis use at 21 years.

Smoking three cannabis joints will cause you to inhale the same amount of toxic chemicals as a whole packet of cigarettes, according to research published in France today.

Cannabis smoke contains seven times more tar and carbon monoxide, the French National Consumers’ Institute concluded in research published in the April edition of its monthly magazine.

The institute tested regular Marlboro cigarettes alongside 280 specially rolled joints of cannabis leaves and resin in an artificial smoking machine.

The tests examined the content of the smoke for tar and carbon monoxide, as well as for the toxic chemicals nicotine, benzene and toluene.

“Cannabis smoke contains seven times more tar and carbon monoxide than tobacco smoke,” the institute’s magazine “60 million consumers” said.

Someone smoking a joint of cannabis resin rolled with tobacco will inhale twice the amount of benzene and three times as much toluene as if they were smoking a regular cigarette, the study said.

Smokers of pure cannabis leaves will also inhale more of these chemicals than from a normal cigarette, though the amount varies depending on the quantities.

“Smoking three joints every day — which is becoming frequent — makes you run the same risks of cancer or cardio-vascular diseases as smoking a packet of cigarettes,” the magazine said.

Cannabis is “by far” the most popular illicit drug in France, it said. The number of cigarette smokers and people drinking alcohol fell in 2005, while the number of cannabis users has increased in France over the past five years.

Source: AFP, Australian Foreign Press March 27, 2006

“The only real way to tackle youth smoking is to make it no longer seem like the norm in adult society. That means more smoke-free places, no tobacco advertising and more adults quitting.”
New research from Sapparo in Japan sugge that young people who smoke start to suffer significant damage to their hearts and blood vessels at a much earlier age than had previously been thought.An advanced new scanning technique revealed that smokers aged between 18 and 35 showed signs of damage associated with coronary heart disease even though they appeared healthy on standard cardiac diagnostic tests. Most previous research had suggested that such effects began to accumulate in a significant way only after many years of smoking.

In 1999:

• youths who reported participating in violence during the past year were more likely to use alcohol and illicit drugs during the past month than youths who did not report past year violence.
• 18% of youths who had participated in a serious fight at school or work reported past month use of illicit drugs compared with 7 of youths who had not participated in a serious fight during the past year.
• veterans accounted for more than 65,000 admissions for substance  abuse treatment.
• the criminal justice system was the most common source of drinkers referrral for all veterans.
• 44% of heavy drinkers aged 18 to 25 had used illicit drugs in the past month compared with 26% of binge’ drinkers (persons who had five or more drinks on the same occasion at least once in the past month) in the same age group.

Marijuana Impairs Driving-Related Skills and Workplace Performance.Marijuana use impairs driving-related functions and is linked to a pattern of behaviors that leads to poor job performance, according to two NIDA-supported studies on the effects of marijuana on human performance. Findings from the studies were presented at NIDA’s first National Conference on Marijuana Use.
At NIDA ‘s National Conference on Marijuana Use, Dr. Stephen Heishman presented data from laboratory studies showing that marijuana impairs functions important to driving. Figures from previous studies of automobile accident victims show that from 6 to 12 percent of nonfatally injured drivers and 4 to 16 percent of fatally injured drivers had tetrahydrocannabinol (THC), the psychoactive ingredient in marijuana, in their bloodstream. One study showed that 32 percent of drivers in a shock trauma unit in Baltimore had marijuana in their bloodstream. However, in most of these studies, the majority of subjects who tested positive for THC also tested positive for alcohol, making it difficult to single out THC’s effect on driving.
In a laboratory study at NIDAs Addiction Research Center in Baltimore that controlled for alcohol’s confounding effect, Dr.Stephen Heishiman,a research psycologist in clinical pharmocology, tested marijuana’s effects on the functional components of driving. Study subjects smoked a marijuana cigarette, waited 10 minutes. then smoked another cigarette. Both cigarettes contained either 0. 1.8. or 3.6 percent THC. Twenty minutes after smoking the cigarettes. the subjects were given a standard sobriety test similar to a roadside sobriety test. The test showed that marijuana significantly impaired their ability to stand on one leg for 30 seconds or touch their finger to their nose. As the dose of THC increased, the subjects swayed more, raised their arms, and had to put their feet down in an attempt to maintain their balance. Subjects also committed 2.5 times more errors when they attempted to touch their nose with their finger.
The data from these laboratory studies show that marijuana impairs balance and coordination – functional components important to driving – in a dose-related way, said Dr. Heishman. These effects may be related to reported marijuana-induced impairment of automobile driving, he stated.
Highway and urban driving studies conducted in the Netherlands show less impact on actual driving. However. these driving studies used very low doses of marijuana for safety reasons, Dr. Heishman said. Future research using appropriate safety measures should test the effect of higher doses of marijuana on driving as well as the combined effect of marijuana and alcohol on driving, he concluded.

Dr. Wayne Lehman of Texas Christian University looked at how marijuana affects job performance. A series of surveys he conducted among 4,600 municipal employees in four cities in the Southwest indicated that 8 percent of employees had smoked marijuana in the past year, and a large percentage of these users had smoked marijuana in the past month, Dr. Lehman said.
‘Employees who report marijuana use are different from nonusers,” said Dr. Lehman. They are much more likely than nonusers to have arrest histories, low self-esteem, high rates of depression, and friends who are deviant. Many marijuana smokers also have alcohol-related problems. One-third of marijuana users in the suneys reported they drank frequently. one-half said they got drunk, and 60 percent reported a problem with alcohol use, according to Dr. Lehman.
This behavioral pattern in the personal backgrounds of marijuana-smoking employees was associated with negative attitudes toward work and job performance, Dr. Lehman said. The surveys found that marijuana users were less likely than nonusers to commit to the organization. had less faith in management, and experienced low job satisfaction. These workers reported more absenteeism, tardiness, accidents, workers’ compensation claims, and job turnover than workers who had not used marijuana. They were also more likely to report to work with a hangover, miss work because of a hangover, and be drunk or use drugs at work.
These data indicate that marijuana use is strongly associated with problematic alcohol use and a pattern of general deviance that leads to impaired behaviors and poor workplace performance, Dr. Lehman concluded.

Child abuse can lead to substance abuse

Carl Anderson, a Harvard instructor in psychiatry and a research associate in McLean Hospitals Developmental Biopsychiatry Research Laboratory and Brain Imaging Center, and his colleagues found that repeated sexual abuse affects the blood flow and function of a key brain region related to substance abuse, the cerebellar vermis. This part of the brain has been recently implicated in the coordination of emotional behavior, is strongly affected by alcohol, cocaine, and other drugs of abuse, and may help regulate dopamine, a neurotransmitter critically involved in addiction.
‘Damage to this area of the brain may cause an individual to be particularly irritable, and to seek external means, such as drugs or alcohol, to quell this irritability,” said Anderson.
Anderson said the teams findings enhance understanding of the developmental mechanisms of childhood sexual abuse, which may result in new methods of treatment for child-abuse survivors.

Scientists at the National Institute on Drug Abuse (NIDA) have demonstrated that laboratory animals will self-administer marijuana’s psychoactive component, THC (delta-9-tetrahydrocannabinol), in doses equivalent to those used by humans who smoke the drug.
Self-administration of drugs by animals, long considered a model of human drug-seeking behavior, is characteristic of virtually all addictive and abused drugs.
“This study is simple and its findings are clear,’ says NIDA Director Dr. Alan I. Leshner. ‘Animals will work to get THC. This emphasizes further the similarity between marijuana and other abusable, addicting substances. Both animals and humans will work to acquire access to marijuana in the same way that both animals and humans change their behavior to get other drugs of abuse, like cocaine and heroin.”
“This is the first study in which it has been possible to show that monkeys or other research animals will self-administer THC. There are many factors which may explain this behavior, including the fact that in our study we used doses of THC that are directly comparable to doses in marijuana smoke inhaled by humans,” Dr. Goldberg says.
Before the study began, the scientists first established self-administration behavior in squirrel monkeys that received repeated intravenous injections of cocaine after pressing a lever 10 times for each injection. At the start of the study, the researchers replaced cocaine with saline solution and the animals’self-administration stopped. When saline was replaced with THC in a solution that would rapidly pass from blood to the brain, the animals resumed self-administration, rapidly pressing the lever to obtain on average 30 injections of THC during each of a series of 1-hour sessions. Treatment with a compound that prevented TI-IC from binding to cannabinoid receptors on brain cells almost completely eliminated self-administration of THC, but had no effect in another group of monkeys self-administering cocaine under identical conditions.
“The drug-seeking behavior in these animals was comparable in intensity to that maintained by cocaine under identical conditions, and was obtained from a range of doses comparable to those self-administered by humans smoking a single marijuana cigarette,” Dr. Goldberg says. “This finding suggests that marijuana has as much potential for abuse as other drugs of abuse, such as cocaine and heroin.”

People who begin using marijuana early are more likely than others to become dependent, new findings show.
In a study of over 2700 marijuana users in Ontario, Canada, those who started smoking at 17 years or later were twice as likely to eventually quit compared with those who started at 14 years or younger. “We believe this study has uncovered important information regarding the effects of patterns of marijuana use on the risk of desistance and progression to marijuana- related harm Dr. David J. DeWit, of the Centre for Addiction and Mental Health, in London, Ontario.
“We observed a significant.. relationship between frequency of lifetime marijuana use and marijuana desistance,” the authors say.
Compared with infrequent use, a lifetime frequency of 100 to 199 uses predicted an almost five fold higher likelihood of developing marijuana disorders, they report.
Prevention programs that are effective in delaying initiation of marijuana use until the age of 16 and beyond may greatly diminish the likelihood of prolonged consumption and consequently serve to avert serious problems later in life” DeWit and colleagues conclude.

People who begin using marijuana early are more likely than others to become dependent, new findings show.
In a study of over 2700 marijuana users in Ontario, Canada, those who started smoking at 17 years or later were twice as likely to eventually quit compared with those who started at 14 years or younger. “We believe this study has uncovered important information regarding the effects of patterns of marijuana use on the risk of desistance and progression to marijuana- related harm Dr. David J. DeWit, of the Centre for Addiction and Mental Health, in London, Ontario.
“We observed a significant.. relationship between frequency of lifetime marijuana use and marijuana desistance,” the authors say.
Compared with infrequent use, a lifetime frequency of 100 to 199 uses predicted an almost five fold higher likelihood of developing marijuana disorders, they report.
Prevention programs that are effective in delaying initiation of marijuana use until the age of 16 and beyond may greatly diminish the likelihood of prolonged consumption and consequently serve to avert serious problems later in life” DeWit and colleagues conclude.

SOURCE: Preventive Medicine 2000;31 :455-464