Cannabis: Health issuesDespite the controversy surrounding the effects of Cannabis, some of the medical effects cannot be disputed.
In quantity, Cannabis smoking can cause the same health problems as tobacco smokers, such as bronchitis, emphysema, and bronchial asthma. It is to be noted, however, that while a habitual tobacco smoker may consume twenty to forty cigarettes (one to two packs) in a day, a habitual marijuana cigarette (joint) smoker consumes far fewer. It should also be noted, however, that marijuana users usually inhale much deeper breaths (hits) and hold them in for much longer in order to absorb as much of the THC in the smoke as possible. Many marijuana users wishing to minimize risks of lung damage instead choose to either eat their dosages or use water pipess or vaporizers, which are known to seriously reduce and perhaps (for vaporizers) eliminate lung damage. Although very limited research has been conducted on the effects of cannabis when consumed orally, it is commonly theorized that its harm is negligible, undoubtedly far less harmful than oral consumption of alcohol.
Inhalation of any sort of smoke is unhealthy. Marijuana smoke (and nearly all other smoke) contains known toxins. Using a water pipe or bong, believed to make smoking healthier, is actually worse for the user. This is because even though particulate matter is reduced in the smoke, THC concentration is also reduced, at a greater percentage than the particulate matter. Thus, one must smoke more to get the same amount of THC, exposing the lungs to more particulate matter. The highest ratio of THC to particulate matter is an unfiltered marijuana cigarette, or joint.
The THC molecule and related compounds (which, by themselves, are not carcenogenic) are usually detectable in drug tests for approximately one month after smoking cannabis. This detection is possible because THC metabolites are stored for long periods of time in fat cells, although the harmfulness of that phenomenon has not been heavily researched at the time of this writing.
Some of the effects of marijuana use also include increased heart rate, dryness of the mouth, reddening of the eyes, impaired motor skills and concentration, and frequently hunger which is often accompanied by greater enjoyment of food's taste and aroma. Although it is commonly stated as fact that marijuana use suppresses the immune system, this effect has not been confirmed by studies on humans using common recreational doses. Occasionally, hallucinations, fantasies and paranoia are reported, typically with inexperienced users under the influence of high potency cannabis.
One highly controversial aspect of cannabis use is its effect on one's ability to drive. Studies on the subject have been limited, and generally did not take into account relevant factors like age and alcohol intoxication. Most studies that have taken these factors into account have concluded that cannabis' effect on driving ability is negligible, and may be more positive than negative, due to the tendency of intoxicated individuals to drive much slower and more cautiously. The United Kingdom's Transit Research Laboratory (TRL) concluded in a 2001 study cannabis intoxication plays a relatively insignificant role in vehicular accidents. Specifically, intoxicated individuals had a lowered "tracking time" (ability to control the steering wheel) but were otherwise normal and, unlike alcohol (which reduces activity in the part of the brain that recognizes and responds to risks), participants were aware of the effects and compensated by driving more slowly and cautiously. Similar conclusions have been reached by studies maintained by the federal governments of Australia, United Kingdom, New Zealand and the United States (see here for a list of studies). The studies that have concluded that cannabis has a significant negative effect on driving ability generally involve the use of roadside sobriety tests as an indicator of reduced ability. For example, see this NIDA report.