The long-term use of cannabis, particularly at high intake levels, is associated with several adverse psychosocial features, including lower educational achievement and, in some instances, psychiatric illness. There is little evidence, however, that long-term cannabis use causes permanent cognitive impairment, nor is there is any clear cause and effect relationship to explain the psychosocial associations. There are some physical health risks, particularly the possibility of damage to the airways in cannabis smokers.

Overall, by comparison with other drugs used mainly for ‘recreational’ purposes, cannabis could be rated to be a relatively safe drug.

The author concludes that there is little evidence that long-term cannabis use causes permanent cognitive impairment or has an adverse effect on global intelligence. Iversen does acknowledge, however, that smoking marijuana long-term may cause "the possibility of damage to the airways," though he admits that "little progress has been made in quantifying such risks." The author also notes that various longitudinal studies have found an association between the long-term, heavy use of cannabis and specific adverse psychosocial features, including lower educational achievement, though he acknowledges that there exists no "clear cause and effect relationship to explain the psychosocial associations."
Abbreviations: THC, Δ⁹-tetrahydrocannabinol
 

Read Complete Study in PDF File Here

HempPharm.com Comments: So, basically there is absolutely no legal basis for prohibition of either hemp or medical cannabis, not from a criminal point of view and certainly not from a public health point of view; go and try to put cigarettes through the same tests and see how it compares to cannabis, but hey, cigarettes are ok even if they kill you and are not a medicine, go figure! Where is the logic? Vaporized Cannabis has only benefits for the human body!
 

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Minor Respiratory Complications, No Decrease In Pulmonary Function Associated With Long-Term Marijuana Smoking, Study Says
February 15, 2007 - West Haven, CT, USA

West Haven, CT: Long-term smoking of cannabis is associated with an elevated risk of respiratory complications, including an increase in cough, sputum production, and wheezing, but not a decline in pulmonary function, according to a review published in the February issue of the journal Archives of Internal Medicine.

Investigators at the Yale University School of Medicine conducted a systematic review of studies published between 1966 and 2005 that assessed the effects of marijuana smoking on pulmonary function and respiratory complications.

The data failed to show an association between long-term marijuana smoking and airflow obstruction (emphysema), as measured by airway hyperreactivity, forced expiratory volume (FEV), and other measures, investigators reported. Short-term use of cannabis was associated with bronchodilation.

Investigators did find that long-term marijuana smoking was associated with an increased risk of certain respiratory complications -- including cough, bronchitis, phlegm, and wheezing. Most of these complications persisted even after researchers adjusted for tobacco smoking.

Previous reviews of long-term cannabis smoking have noted similar respiratory complications, though an association between cannabis use and lung and/or upper aerodigestive tract (UAT) cancers has not been found.

Authors suggested that cannabis inhalation via specialized delivery systems such as vaporizers would likely yield different results.

Cannabis vaporization limits users' intake of respiratory toxins by heating cannabis to a temperature where cannabinoid vapors form (typically around 180-190 degrees Celsius), but below the point of combustion where noxious smoke and associated toxins (e.g., carcinogenic hydrocarbons) are produced (near 230 degrees Celsius). According to clinical trial data published last year in the Journal of Pharmaceutical Sciences, vaporization is a "safe and effective" cannabinoid delivery system for individuals desiring the rapid onset associated with inhalation, but who wish to avoid the respiratory risks of smoking.

"The final pulmonal uptake of THC is comparable to the smoking of cannabis, while avoiding the respiratory disadvantages of smoking," investigators in that study reported.

Full text of the study, "Effects of marijuana smoking on pulmonary functions and respiratory complications: a systemic review" appears in the current issue of the Archives of Internal Medicine.