List of effects
Cannabis has a broad spectrum of possible cognitive, behavioural, and physiological effects, the occurrence of which vary from user to user. Some of these are the intended effect desired by users, some may be considered desirable depending on the situation, and others are generally considered undesirable. Users of cannabis report that these kinds of effects are more often produced by the sativa species of Cannabis.
Cannabis also has effects that are predominantly physical or sensory, widely believed to be more common with the indica species.
Cognitive effects
* Short or long-term psychosis/schizophrenic disorders that begin in some young users
* Varying amounts of paranoia and anxiety in some users
* Loss of coordination and distorted sense of time in some users
* Impairment of short-term memory in some users
* Auditory or visual hallucinations at high doses in some users
* Increased mental activity, like metacognition and introspective or meditative states of mind in some users
* Relaxation or stress reduction in some users
* Entheogenesis (eg. per Rastafarian users, more "Jah-Vibrations") in some users
Although studies have not proven altogether conclusive on the subject, recent work suggests that the cognitive effects of cannabis use under 70 joints a week are wholly impermanent, and that most afformentioned effects subside after about a month.
behavioural effects
* Varying degrees of euphoria and feelings of well-being
Physiological effects
* Antiemetic properties (in moderate doses)
* Lowered intraocular pressure, beneficial to glaucoma patients and sufferers of certain types of headaches, cramps, and eye pain.
* Dilation of blood vessels (vasodilation), resulting in:
o Increased blood flow and heart rate (possibly even tachycardia)
o Reddening or drying of eyes
* Lower blood pressure while standing. Higher blood pressure while sitting (note that this can lead to instances of orthostatic hypotension, also known as head rush).
* Increased appetite (often referred to as "the munchies"), an effect of stimulation of the endocannabinoid system, which affects body weight, insulin resistance, and dyslipidemia. though recent and anecdotal evidence also points to it as an appetite suppressant.
* Varying degrees of dry (cotton) mouth
* Dilation of alveoli (air sacs) in lungs, resulting in deeper respiration and increased coughing.
Lethal dose
It is generally considered to be impossible to achieve a lethal overdose by smoking cannabis. According to the Merck Index, 12th edition, the LD50, the lethal dose for 50% of rats tested by inhalation, is 42 mg/kg of body weight. That is the equivalent of a 165 lb (75 kg) man ingesting all of the THC in 21 one-gram cigarettes of high-potency (15% THC) cannabis buds at once, assuming no THC was lost through burning or exhalation. For oral consumption, the LD50 for rats is 1270 mg/kg and 730 mg/kg for males and females, respectively, equivalent to the THC in about a pound of 15% THC cannabis. Only with intravenous administration - an unheard-of method of use - may such a level be even theoretically possible. Also, there is no practicality of overdosing, and virtually no chance of accidental overdose while smoking cannabis, considering the ratio of cannabis required to saturate cannaboid receptors to the amount of cannabis required to have a fatal over dose is 1:40,000.
There has only ever been one recorded verdict (although not ultimately upheld) of fatal overdose due to cannabis. In January 2004, Lee Maisey of Pembrokeshire, Wales was found dead. The coroner's report stated "Death due to probable cannabis toxicity". It had been reported that Maisey smoked about six joints a day. Mr. Maisey's blood contained 130 nanograms per milliliter (ng/ml) of the THC metabolite THC-COOH. However, the validity of the finding did not stand up well under review. As reported on 2004-01-28 in the Neue Züricher Zeitung, the Federal Health Ministry of Switzerland asked Dr. Rudolf Brenneisen, a professor at the department for clinical research at the University of Bern, to review the data of this case. Dr. Brenneisen said that the data of the toxicological analysis and collected by autopsy were "scanty and not conclusive" and that the conclusion "death by cannabis intoxication" was "not legitimate."
Health issues and the effects of cannabis
The most significant confounding factor is the use of other drugs, including alcohol and tobacco, by test subjects in conjunction with cannabis. When subjects using only cannabis were combined in the same sample with subjects using other drugs as well, researchers could not reach a conclusion as to whether their findings were caused by cannabis, other drugs, or the interaction between them. In addition, research using cannabis is heavily restricted in many countries, making it difficult to get new studies funded or approved. Since there are so many different compounds in cannabis, it is difficult to predict or accurately measure its effects. Some conclusions established with some degree of certainty that cannabis is less likely to cause emphysema or cancer than tobacco; that it is unlikely to cause birth defects or developmental delays in the children of users, and in a study done by the University of California Los Angeles in 2006, that even heavy marijuana smokers do not increase their risk for lung cancer. According to a United Kingdom government report, using cannabis is less dangerous than both tobacco and alcohol in social harms, physical harm and addiction.
Newer research has also shown that cannabis use is generally higher among sufferers of schizophrenia, but causality has not been established and confirmed that sustained early-adolescent cannabis use among certain genetically predisposed individuals has an elevated correlation with certain mental illness outcomes, ranging from psychotic episodes to clinical schizophrenia.
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The full fact sheet/report is here:
http://www.medic8.com/medicines/Marijuana.html
As for the language semantics...you "could" or "may possibly" incur negative physical effects from using any number of drugs. Drugs don't ALWAYS cause their harmful effects. Marijuana is much less potent than harder drugs and so it is less likely to induce negative effects. However, the possibility of a negative effect remains.
