A March 30, 2005 article in the journal Psychiatric Research by Jason Schiffman et. al. reported:

"Findings suggest that regular cannabis users are significantly more prone to cognitive and perceptual distortions as well as disorganization, but not interpersonal deficits, than non-regular users and those who have never used.

Additionally, the onset of schizotypal symptoms generally precedes the onset of cannabis use. The findings do not support a causal link between cannabis use and schizotypal traits."
3/30/05 Psychiatry Research

Neutral

A March 2005 article in the journal Addiction titled "Tests of Causal Linkages Between Cannabis Use and Psychotic Symptoms" stated:

"Regression models adjusting for observed and non-observed confounding suggested that daily users of cannabis had rates of psychotic symptoms that were between 1.6 and 1.8 times higher than non-users of cannabis....

The results of the present study add to a growing body of evidence suggesting that regular cannabis use may increase risks of psychosis.

The present study suggests that:

1. the association between cannabis use and psychotic symptoms is unlikely to be due to confounding factors; and

2. the direction of causality is from cannabis use to psychotic symptoms."
   3/05 Addiction

Con

Researchers Maria L. de Ceballos et al. wrote in their 2/23/05 article "Prevention of Alzheimer's Disease Pathology by Cannabinoids: Neuroprotection Mediated by Blockage of Microglial Activation," published in the Journal of Neuroscience :

"Our results indicate that cannabinoid receptors are important in the pathology of AD [Alzheimer's Disease] and that cannabinoids succeed in preventing the neurodegenerative process occurring in the disease."
2/23/05 Jrnl. of Neuroscience

Researchers from the Movement Disorders Centre, Dept. of Neurology at Charles University, Prague, Czech Republic, wrote in their "Survey On Cannabis Use In Parkinson's Disease" published in the journal Movement Disorders :

"An anonymous questionnaire sent to all patients attending the Prague Movement Disorder Centre revealed that 25% of 339 respondents had taken cannabis and 45.9% of these described some form of benefit....

The late onset of cannabis action is noteworthy. Because most patients reported that improvement occurred approximately two months after the first use of cannabis, it is very unlikely that it could be attributed to a placebo reaction."
9/04 Movement Disorders

Pro

Dennis M. Israelski, M.D., et. al, in their research study, "Marijuana Use is Associated with Better Adherence to ART Among HIV-infected Persons with Moderate to Severe Nausea," presented at the July 2004 XV International AIDS Conference, reported:

"Adherence to antiretroviral therapy (ART) is essential to successful treatment of HIV-infection. Two recent studies reported a negative correlation between marijuana use and adherence to ART. Some patients, however, report smoking marijuana to improve adherence to ART. We therefore sought to identify which sub-groups of patients may increase or decrease ART adherence with recent marijuana use.

...With a 5% refusal rate, 252 patients completed the interview...Forty-one subjects (24%),

...Examining sub-groups of patients, among those with nausea, marijuana users were more likely to be adherent than non-users (OR=3.3), while among those without nausea, marijuana users were less likely to be adherent (OR=0.52, p for homogeneity 0.02).

Our data suggest that medicinal use of marijuana may facilitate, rather than impede, ART adherence for patients with nausea..."
7/04 Israelski

In their article "Psychoactive Substance Use and the Risk of Motor Vehicle Accidents," published in the journal Accident Analysis & Prevention, researchers K.L.L. Movig et al. wrote:

"The objective of this study was to estimate the association between psychoactive drug use and motor vehicle accidents requiring hospitalization...

The risk for road trauma was increased for single use of benzodiazepines and alcohol... High relative risks were estimated for drivers using combinations of drugs and those using a combination of drugs and alcohol. Increased risks, although not statistically significant, were assessed for drivers using amphetamines, cocaine, or opiates.

No increased risk for road trauma was found for drivers exposed to cannabis."
7/04 Accident Analysis & Prevention

Wilson M. Compton, M.D., et al., in their article "Prevalence of Marijuana Use Disorders in the United States: 1991-1992 and 2001-2002," published in the Journal of the American Medical Association (JAMA), the researchers wrote:

"Among the adult U.S. population, the prevalence of marijuana use remained stable at about 4.0% over the past decade. In contrast, the prevalence of DSM-IV [psychological classifications of disorders] marijuana abuse or dependence significantly increased between 1991-1992 and 2001-2002, with the greatest increases observed among young black men and women and young Hispanic men.

Further, marijuana use disorders among marijuana users significantly increased in the absence of increased frequency and quantity of marijuana use, suggesting that the concomitant increase in potency of delta-9-THC [one of the active ingredients in marijuana] may have contributed to the rising rates."

The authors offered the following statistics and conclusion:

"...marijuana abuse or dependence increased among marijuana users by 18% from 30.2% in 1991-1992 to 35.6% in 2001-2002...

The potency of delta-9-THC in confiscated marijuana from police seizure increased by 66% from 3.08% in 1992 to 5.11% in 2002...

Moreover, there was no systematic change in the frequency of marijuana use between 1991-1992 and 2001-2001...

Increasing rates of marijuana use disorders among marijuana users in the absence of increased quantity and frequency of use strengthens the argument that the increasing rates may be attributable, in part, to increased potency of marijuana."
5/04 JAMA

Neutral

John Macleod, Ph.D., et al., in their article "Psychological And Social Sequelae of Cannabis and Other Illicit Drug Use by Young People: A Systematic Review of Longitudinal, General Population Studies," published 5/15/04 in The Lancet, the researchers found:

"Available evidence does not strongly support an important causal relation between cannabis use by young people and psychosocial harm, but cannot exclude the possibility that such a relation exists.

The lack of evidence of robust causal relations prevents the attribution of public health detriments to illicit drug use. In view of the extent of illicit drug use, better evidence is needed."
5/15/04 The Lancet

"Results: With the exception of higher drug use in San Francisco, we found strong similarities across both cities. We found no evidence to support claims that criminalization reduces use or that decriminalization increases use.

Conclusions: Drug policies may have less impact on cannabis use than is currently thought."
5/04 AJPH

A study published in January 2004 by the Journal of Acquired Immune Deficiency Syndrome (JAIDS), designed by Prentiss, Power, Balmas, Tzuang and Israelski "to examine the prevalence and patterns of smoked marijuana and perceived benefit" among 252 HIV patients, found;

"Overall prevalence of smoked marijuana in the previous month was 23%. Reported benefits included relief of anxiety and/or depression (57%), improved appetite (53%), increased pleasure (33%), and relief of pain (28%). Recent use of marijuana was positively associated with severe nausea and recent use of alcohol and negatively associated with being Latino.

The findings suggest that providers be advised to assess routinely and better understand patients' indications for self-administration of cannabis. Given the estimated prevalence, more formal characterization of the patterns and impact of cannabis use to alleviate HIV-associated symptoms is warranted.

Clinical trials of smoked and noncombustible marijuana are needed to determine the role of cannabinoids as a class of agents with potential to improve quality of life and health care outcomes among patients with HIV/AIDS."
01/04 Journal AIDS

An October 2003 article in Nature Reviews - Cancer, "Cannabinoids: Potential Anticancer Agents," by Manuel Guzman, Ph.D., reported:

"Cannabinoids -- the active components of Cannabis sativa and their derivatives -- exert palliative effects in cancer patients by preventing nausea, vomiting and pain and by stimulating appetite.

In addition, these compounds have been shown to inhibit the growth of tumour cells in culture and animal models by modulating key cell-signalling pathways.

Cannabinoids are usually well tolerated, and do not produce the generalized toxic effects of conventional chemotherapies."
10/03 Nature Reviews

A placebo-controlled clinical trial designed to determine "the short-term effects of smoked marijuana on the viral load of HIV-infected patients" concluded the following, as reported in the Annals of Internal Medicine (click here to see whole article in PDF format):

"Conclusions: Smoked and oral cannabinoids [marijuana] did not seem to be unsafe in people with HIV infection with respect to HIV RNA levels, CD4 and CD8 cell counts, or protease inhibitor levels over a 21-day treatment."

The accompanying "Summaries For Patients" provided by the journal (click here to read summary in pdf format) stated:

"Patients receiving cannabinoids [smoked marijuana and marijuana pills] had improved immune function compared with those receiving placebo. They also gained about 4 pounds more on average than those patients receiving placebo."
8/19/03 AIM

In a February 2003 article published in the British Journal of Psychiatry (BJP) titled "Adolescent Precursors of Cannabis Dependence: Findings from the Victorian Adolescent Health Cohort," which studied students in Australia from 1992 through 1998 (when they were 20-21 years old), researchers noted the following:

"Results Of 1,601 young adults, 115 met criteria for cannabis dependence. Male gender, regular cannabis use and persistent cigarette smoking independently predicted cannabis dependence. Neither smoking severity nor persistent psychiatric morbidity independently predicted dependence. Regular cannabis use increased risk only in the absence of persistent problematic alcohol use.

Conclusions Weekly cannabis use marks a threshold for increased risk of later dependence, with selection of cannabis in preference to alcohol possibly indicating an early addiction process."
02/03 BJP

A study of 311 young adult twin pairs conducted by Michael T. Lynskey, PhD, of the Washington University School of Medicine, St Louis, MO, and published January 22/29, 2003 in the Journal of the American Medical Association (JAMA) reported:

"Results: Individuals who used cannabis by age 17 years had odds of other drug use, alcohol dependence, and drug abuse/dependence that were 2.1 to 5.2 times higher than those of their co-twin, who did not use cannabis before age 17 years."

The report concluded:

"In particular, early access to and use of cannabis may reduce perceived barriers against the use of other illegal drugs and provide access to these drugs."
1/22/03 JAMA

Neutral

In a study of over 50,000 Swedish conscripts, researchers Stanley Zammit, M.D. and Peter Allebeck, M.D. concluded as published Nov. 23, 2002 in the British Medical Journal (BMJ):

"Cannabis was associated with an increased risk of developing schizophrenia in a dose dependent fashion both for subjects who had ever used cannabis, and for subjects who had used only cannabis and no other drugs.

Conclusions: Cannabis use is associated with an increased risk of developing schizophrenia, consistent with a causal relation. This association is not explained by use of other psychoactive drugs or personality traits relating to social integration."
11/23/02 BMJ

Con

A September 2002 article in the journal Addiction, "Cannabis Use and Psychosocial Adjustment in Adolescence and Young Adulthood," stated:

"Cannabis use, and particularly regular or heavy use, was associated with increased rates of a range of adjustment problems in adolescence / young adulthood -- other illicit drug use, crime, depression and suicidal behaviours -- with these adverse effects being most evident for schoolaged regular users.

The findings reinforce public health concerns about minimizing the use of cannabis among school-aged populations."
9/03 Addiction same sex, same gender, reparative therapy" name="keywords">

Donald P. Tashkin, M.D., in his article "Effects of Smoked Marijuana on the Lung and Its Immune Defenses: Implications for Medicinal Use in HIV-Infected Patients" published in the Journal of Cannabis Therapeutics (JCT), stated:

"Frequent marijuana use can cause airway injury, lung inflammation and impaired pulmonary defense against infection. The major potential pulmonary consequences of habitual marijuana use of particular relevance to patients with AIDS is superimposed pulmonary infection, which could be life threatening in the seriously immonocompromised patient.

In view of the immonosuppressive effect of THC, the possibility that regular marijuana use could enhance progression of HIV infection itself needs to be considered, although this possibility remains unexplored to date."
2001 JCT

Con

"The cumulative data obtained through cell culture studies using various immune cell populations extracted from animals or humans, together with those obtained using animal models of infection, are consistent with the proposition that marijuana and cannabinoids alter immune cell function and can exert deleterious effects on resistance to infection in humans."

Dr. Cabral then concluded:

"However, few controlled longitudinal epidemiological and immunological studies have been undertaken to correlate the immunosuppressive effects of marijuana smoke or cannabinoids on the incidence of infections or viral disease in humans.

Clearly, additional investigation to resolve the long-term immunological consequences of cannabinoid and marijuana use as they relate to resistance to infections in humans is warranted."
2001 JCT

"In practice it has been found that extracts of cannabis [processed whole plant compounds] provide greater relief of pain than the equivalent amount of cannabinoid given as a single chemical entity [such as Marinol]....

Some patients with multiple sclerosis who smoke cannabis [marijuana] report relief of spasm and pain after the second or third puff of a cannabis cigarette. This implies very rapid transit to, and absorption into the central nervous system. The time involved is seconds rather than minutes. "
2001 JCT

In a study published in the journal Nature ("Physiology: A Hunger for Cannabinoids") researchers Raphael Mechoulam et al. found:

"[M]olecules found naturally in the body, as well as in cannabis -- stimulate appetite."
4/12/01 Nature

In a study of "Marijuana Abstinence Effects in Marijuana Smokers Maintained in Their Home Environment," conducted through the University of Vermont, Burlington and the U.S. Air Force, Biomedical Science Corps, and published in the October 2001 issue of the Archives of General Psychiatry (AGP), researchers concluded:

"This study validated several specific effects of marijuana abstinence in heavy marijuana users, and showed they were reliable and clinically significant.

These withdrawal effects appear similar in type and magnitude to those observed in studies of nicotine withdrawal."

Researchers additionally noted the following specifics regarding "withdrawal discomfort," which they stated "increased significantly during the abstinence phases and returned to baseline" when marijuana smoking resumed:

"Craving for marijuana, decreased appetite, sleep difficulty, and weight loss reliably changed across the smoking and abstinence phases. Aggression, anger, irritability, restlessness, and strange dreams increased significantly during one abstinence phase, but not the other."
October, 2001 AGP

Researcher Andrew Johns, in his article "Psychiatric Effects Of Cannabis" published in the February 2001 edition of the British Journal of Psychiatry (BJP), noted:

"An appreciable proportion of cannabis users report short-lived adverse effects, including psychotic states following heavy consumption, and regular users are at risk of dependence.

There is good evidence that taking cannabis leads to acute adverse mental effects in a high proportion of regular users. Many of these effects are dose-related, but adverse symptoms may be aggravated by constitutional factors including youthfulness, personality attributes and vulnerability to serious mental illness....

People with major mental illnesses such as schizophrenia are especially vulnerable in that cannabis generally provokes relapse and aggravates existing symptoms."
February, 2001 BJP

Con

An article in the March, 2001 issue of the Journal of Respiratory Cell and Molecular Biology (JRCMB), states:

"Marijuana tar induced higher levels of CYP1A1 messenger RNA (mRNA) than did tobacco tar, yet resulted in much lower CYP1A1 enzyme activity. These differences between marijuana and tobacco were primarily due to Delta-9-tetrahydrocannabinol....

This complex regulation of CYP1A1 by marijuana smoke and the Delta-9-THC that it contains has implications for the role of marijuana as a cancer risk factor."
March, 2001 JRCMB

Con

Harvard psychiatrist Lester Grinspoon, M.D., wrote in an article published in 2001 in the International Journal of Drug Policy:

"The cannabinoids in whole marijuana can be separated from the burnt plant products by devices already being perfected that will be inexpensive when manufactured in large numbers.

Inhalation is a highly effective means of delivery, and faster means will not be available for analogs (except in a few situations such as parenteral injection in an unconscious patient or one with pulmonary impairment). Furthermore, any new analog will have to have an acceptable therapeutic ratio.

The therapeutic ratio of marijuana is not known because it has never caused an overdose death, but it is estimated on the basis of extrapolation from animal data to be 20,000 to 40,000. The therapeutic ratio of a new analog is unlikely to be higher than that; in fact, it may be less safe because it will be physically possible to ingest more."
2001 International Journal of Drug Policy

"Citizens who live under decriminalization laws consume marijuana at rates less than or comparable to those who live in regions where the possession of marijuana remains a criminal offense."
2000 JPHP

Mohmoud A. ElSohly, Ph.D., in the Journal of Forensic Sciences (JFS) titled "Potency Trends of Delta-9-THC and Other Cannabinoids in Confiscated Marijuana from 1980-1997" wrote:

"The potency (concentration of D9-THC) of marijuana samples rose from less than 1.5% in 1980 to approximately 3.3% in 1983 and 1984, then fluctuated around 3% till 1992. Since 1992, the potency of confiscated marijuana samples has continuously risen, going from 3.1% in 1992 to 4.2% in 1997. The average concentration of D9-THC in all cannabis samples showed a gradual rise from 3% in 1991 to 4.47% in 1997.

Hashish and hash oil, on the other hand, showed no specific potency trends. Other major cannabinoids [cannabidiol (CBD), cannabinol (CBN), and cannabichromene (CBC)] showed no significant change in their concentration over the years."
2000 JFS

A study published in the June, 1999 Journal of Respiratory Cell and Molecular Biology (JRCMB), states:

"Marijuana (MJ) smoking produces inflammation, edema, and cell injury in the tracheobronchial080 mucosa of smokers and may be a risk factor for lung cancer....

We conclude that MJ [marijuana] smoke containing Delta-9-THC is a potent source of cellular oxidative stress that could contribute significantly to cell injury and dysfunction in the lungs of smokers."
6/99 JRCMB

Con

A study published in the December 1998 journal Acta Psychiatrica Scandinavica by researchers Muller-Vahl KR, et. al. titled "Cannabinoids: Possible Role in Patho-physiology and Therapy of Gilles De La Tourette Syndrome" states:

"High densities of cannabinoid receptors were found in the basal ganglia and hippocampus, indicating a putative functional role of cannabinoids in movement and behaviour. Anecdotal reports suggested beneficial effects of marijuana in Tourette's syndrome (TS).

We therefore interviewed 64 TS patients with regard to use of marijuana and its influence on TS symptomatology. Of 17 patients (27%) who reported prior use of marijuana, 14 subjects (82%) experienced a reduction or complete remission of motor and vocal tics and an amelioration of premonitory urges and obsessive-compulsive symptoms.

Our results provide more evidence that marijuana improves tics and behavioural disorders in TS. It can be speculated that cannabinoids might act through specific receptors, and that the cannabinoid system might play a major role in TS pathology."
12/98 Acta Psychiatrica Scandinavica

Pro

Researcher H. Thomas, in his article "Psychiatric Symptoms in Cannabis Users" published in the August, 1993 edition of the British Journal of Psychiatry (BJP) stated:

"Cannabis use can lead to a range of short-lived symptoms such as depersonalisation, de-realisation, a feeling of loss of control, fear of dying, irrational panic and paranoid ideas."

The article concluded:

"The evidence that cannabis has a causative role in chronic psychotic or affective disorders is not convincing, although the drug may modify the course of an already established illness."
August, 1993 BJP

Neutral