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Overview: The Physiological, and Neurological effects of Marijuana Use in Humans.
Alcohol and tobacco are two of the most commonly used drugs in the United States today. Their legality is well established, with restriction, on the basis of age and partly in turn the implicit ability to judge as a mature person their risks to overall health and well being; so an informed decision can be made on the question of whether or not they are worth using personally. Interestingly, this liberty is not extended to a class of illegal drugs that the mere possession of any of which can result in fines and penalties, including confinement to a correctional facility. In this subset of illegal drugs there is yet a further distinction between different drugs, in the severity of the penalty for their illegal use, possession, or distribution. While some people accept these laws uncritically, others have debated for a long time their justification, some in favor of upholding them and others in favor of taking a second look at and repealing some of them. No matter the view, a large component of the discussion invariably centers on the biological effects of the drugs as a means of understanding the ethical arguments in favor of prohibiting or allowing their use. One drug, marijuana, has particularly captured the attention of people across the country. The notoriety and debate regarding marijuana could simply be a reflection of its popularity with people, or it could stem from biological evidence which suggests that the drug is comparable with legal drugs alcohol and tobacco as far as the risks of potentially adverse effects are concerned. It may be that its biological profile of effects contributes to its relative popularity, both of which interact to shine the spotlight on cannabis use, and make it something of public interest. We intend here to provide a brief overview of the biological effects of cannabis use in humans, for a basic understanding of what is being agreed upon when a user contracts to use cannabis.
The psychoactive drug Cannabis, commonly known today as marijuana, green, or pot, is derived from the Cannabis Sativa plant. Routes of administration include smoking, ingestion, and rarely, rectal insertion of a solution including oil and water. Tetrahydrocannibanol (THC), the active ingredient in marijuana, is several times more pervasive, and rapidly absorbed (in seconds) in the blood of someone who has smoked marijuana, as opposed to eating or drinking it, wherein it may take an hour to feel the effects. It is responsible for the acute, physiological effects experienced shortly after use, and a myriad of effects on the heart, brain, and lungs which may become more pronounced over long term or chronic use. It has been shown that after smoking marijuana, a person's heart rate increases typically anywhere from 20-50%, and may sometimes double. An increase in heart rate, tachycardia is not believed to be a direct effect of marijuana on the heart; rather it is an indirect result of changes which occur in the autonomic nerves that preside over the regulation of heart rate. Other acute effects frequently reported are the reddening or prominence of bloodshot eyes, which can be attributed to a swelling of the conjunctivas blood vessels, and dry mouth, due to reduced salivation. The user will also, often times experience an increase in appetite. Euphoria and elation predominate initially, followed by a period of lingering drowsiness, which some users may try to delay or subvert by taking repeated doses. Learning and athletic performance reliably suffer as there is difficulty concentrating, remembering, or coordinating and balancing one's movements; these are trumpeted as the hallmarks of marijuana use . Some people report being detached and experiencing a dissolution in deed and perception known as depersonalization, which is, among the more variable effects that not all of, or even most people might experience, including altered sense of time, anxiety, and sharper vision coupled with visual distortions. While the effects described here occur often enough in people that use marijuana to be relevant and repeated with regularity, with the exception of a few, because of people's varying experiences due to common factors such as dose, prior usage history, experience, THC content, and some would even argue setting and expectations although research hasn't proven it, they don't occur in all users or in the vast majority of times following use.
Cannabinoid receptors are sites in the brain that correspond to the endogenous neurotransmitter anandamide. Tetrahydrocannibanol acts by attaching to cannabinoid receptors on nerve cells in multiple regions of the brain. Those regions of the brain with an abundance of cannabinoid receptors are therefore more prone to the influence of THC, and as a result the more consistent and apparent effects of marijuana use mostly have to do with functions that are regulated by areas of the brain most susceptible to THC.. When THC in marijuana attaches to cannabinoid receptors in various regions of the brain, one area affected heavily is the Hippocampus, which is responsible for learning and memory vital to success in school. Other regions also influenced considerably include the Cerebellum, responsible for body movement and coordination, the Cerebral Cortex, agent of higher cognitive functions, the Nucleus Accumbens, a reward center, and the Basal Ganglia, also involved in movement control. Researchers and others alike tend to be especially interested in the Nucleus Accumbens, an aggregation of neurons in the forebrain thought to have a strong bearing on reward, pleasure, and addiction among other things. Euphoria and bliss, the main effects sought though cannabis use, occur in tandem with increased levels of dopamine in the Nucleus Accumbens, a finding that is also characteristic of most every other recreational drug. The Hippocampus is another region of the brain that draws a lot of attention with regard to marijuana use. Neurons in the Hippocampus control memory and related learning functions, so as people get older and lose neurons their ability to remember things decreases. THC accelerates this process by aging neuron cells prematurely, which might hasten the imminence of their death and impair memory in the user. The persistence of this effect, although not at this time thought to be permanent, is longer than the period of intoxication and probably less inclined to wear off with more chronic use.
If someone smokes cigarettes for a week and never again, we can conclude with reasonable certainty that it won't affect their long term health prognosis. However, if the same person smokes for 30 years, bravely assuming that they are not already suffering from, most likely they are at an increased risk for lung cancer, heart disease, and other ailments that only develop over long term use. Much in the same way, research today indicates that using marijuana in the short term does not have any permanent adverse effect in humans. Less certain though, is whether or not long term Cannabis use is to the detriment of the user. There are several purported long term effects of marijuana use that have been studied; some are more credible than others. These effects pertain to the individual who has used marijuana daily, heavily, for many, many years. As to which factor would have a greater bearing on our definition of a heavy, long term user, frequency of use has precedent over the quantity of dose. Research has provided considerable evidence that cannabinoids in marijuana, particularly THC, induce immunological changes in rodent animals in the cell-mediated and humeral immune system. The method used to show impaired cell-mediated immune system function is a decreased lymphocyte response in reaction to T-cell mitogens. To demonstrate an impaired humeral immune system the same method is used, except that the muted reaction is in response to B-cell mitogens, T-cells being characteristic of the cell mediated immune system, and B-cells being characteristic of the humeral immune system. Due to these changes, the result is an increased risk of bacterial or viral infection. The relevance of these findings is mitigated however, because the doses required in order to incur these changes have been very high, which adds to the stand alone problem of applying results in rodents to humans. Another obvious concern is that the evidence does not address the possibility that tolerance would develop in humans, perhaps making these findings irrelevant altogether. In the limited human experimental and clinical data, there is unresolved, likely evidence that THC impairs cell-mediated immune system function. What to make of studies that have implicated THC in suppressed immune system function is uncertain because the expectation is that reduced immune system function would result in an increase of infectious diseases, yet there has been no epidemiological outbreak of diseases among chronic heavy cannabis users. One study of HIV positive gay men suggests that their continued use of marijuana did not put them at an increased risk of worsening to AIDS. Considering the extent of marijuana use in western society, reconciled with the fact that there has been no epidemiological outbreak of infectious diseases among users, the evidence is in favor of it being unlikely that smoking cannabis leads to major dysfunction in the immune system. It is not as easy to rule out marijuana use in minor immune system impairment that cannot be as easily detected, but would instead take the form of an unsuspecting cold or other common, bacterial or viral illness.
Healthy young adults who use Cannabis do not show any prolonged strain on their cardiovascular system, as the effect is comparable to common stress. People with preexisting heart conditions such as atherosclerosis however, appear to be at a special risk and are advised to abstain from cannabis use. In chronic heavy users who smoke cannabis, the effects on the respiratory system are similar to a person who smokes tobacco. Most of the health problems in the respiratory system mutual to tobacco and chronic heavy marijuana use arise because of the method of administration, smoking, not because of anything that can be isolated as a byproduct of the cannabinoids. Coughing, wheezing, and sputum production, all which are symptoms of chronic bronchitis, can result from chronic heavy cannabis use. Additionally, chronic bronchitis and cancer of the respiratory tract are probably a more common occurrence in heavy chronic marijuana users for the same reason they are more common in tobacco smokers. A preexisting respiratory condition such as asthma might be exacerbated by smoking cannabis; the same concern with a preexisting heart condition, and the reason why people with respiratory illnesses are advised not to smoke cannabis. Evidence indicates that chronic heavy marijuana use causes microscopic changes in lung tissue, like those that occur prior to lung cancer. At this time it is debated whether or not cannabis smoke causes cancer, with certain studies indicating it does, and others, very recently showing otherwise, that it does not. Although it remains to be proven definitively, the cancer-marijuana link probably presents the most ominous risk in the perception of a casual cannabis user who does not smoke tobacco, and plausibly even in users that smoke cannabis and tobacco, out of fear that the risks may be mounting to cause for a reconsideration of their habits. It's worth noting that even if it is proven beyond any doubt that smoking cannabis causes cancer in chronic heavy users, the results would by and large be insignificant to the typical, infrequent user, but still persuade some to discontinue cannabis use, or use cannabis less frequently, and others not to begin.
Long term cannabis use probably has undesired consequences in the reproductive system for males and females. In females, levels of Lutropin, a hormone produced by the Anterior Pituitary gland that triggers ovulation, seem to be affected by chronic use; it is likely that cannabis causes disruptions to the ovulatory cycle. Pregnant women who smoke cannabis risk low birth weight and less certainly, in utero birth defects that have been shown in animal studies. Lifestyle factors may play a role; in one study, pregnant rats on diets varying in protein content were administered cannabis, the rats on high protein diets fared better in their respective pregnancies than those rats on a low protein diet. Nevertheless, pregnant women should probably exercise additional caution and abstain from cannabis use. In males, chronic cannabis use may result in decreased testosterone secretion, and reduced sperm production and viability, though confidence in these results is subject to appraisal. In general, healthy young men are probably affected insignificantly, while children and men with fertility problems are in a group that should have increased concern.
Experimental, clinical, and epidemiological evidence has shown that cannabis dependence can develop among heavy users. A fair amount of evidence shows that some users develop a tolerance to the effects of the cannabis and show withdrawal symptoms when use is abruptly discontinued. Also, epidemiological and clinical evidence points to some users who report being unable to control their use and even at the cost that it has a negative effect on their personal and social life. A cannabis dependence syndrome has been secondary, overlooked many times because people affected also have a more pressing problem with narcotic or stimulants drugs. Another reason that cannabis dependence has presumably escaped the available perception of people is that few have requested treatment for it. On balance, marijuana commands a view of one that it is not liable to be one of the traditional addicting drugs. In any case, it should be an objective to find out more about cannabis dependence syndrome, especially a model that speaks to its elements, a necessary first step to amassing statistics on its occurrence, and also of some importance there should be work towards a method for treating the dependence, perhaps observing from already established treatment methods for dependence on other substances. The view is that chronic marijuana use does not cause severe cognitive impairment; however, it is likely that it causes subtle changes in higher cognitive function. Areas mutual to complex intellectual processes such as memory, and attention and organization and assimilation of complex information are suspect to being indefinitely impaired in a long term, heavy cannabis user. It is unclear if prolonged abstinence would reverse these effects. This would, like most long term effects described so far, have some people at close attention, namely those people who are not very intelligent to begin with, and those whose chosen endeavors require a high mental capacity; others should probably not see this is as something pronounced, of impressive concern. Heavy chronic cannabis use does not cause structural brain damage, though this does not rule out changes at the receptor level. Psychosis is one of the more outlying effects sometimes associated with cannabis use. Research studies suggest that cannabis use can trigger an acute psychosis in people with genes that predispose them to it. One study followed a group from birth to young adulthood and found that for those with a gene variant that predisposed them to developing psychosis, and who also smoked marijuana in their teens, the risk jumped exponentially. Those in the group absent the gene had little or no added risk.
The task of summarizing the adverse effects of marijuana use which normally persist beyond intoxication in otherwise healthy people doesn't take long; there are none, disallowing at risk persons such as pregnant women, who risk compromising the fetus to a low birth weight, and those with a predisposition to psychosis, who risk precipitating psychotic symptoms. During intoxication, the primary adverse effects include cognitive impairment and a decrease in motor skills, as well as in some inexperienced users, anxiety or paranoia. In long term use, which we defined earlier as daily use over a period of many years, there appears to be several major undesired effects, some are very likely and others have not yet been confirmed by research. Of those which are very likely, respiratory illness such as chronic bronchitis, and changes to the tissue that precede cancer, due to the method of administration, smoking, A high degree of credibility is also maintained in a cannabis dependence syndrome that is established over long term use, and subtle cognitive impairment that might be permanent. Those effects which have been discussed considerably but not confirmed by research include an increased risk of cancers of the pharynx, oral cavity and esophagus, an increased risk of birth defects in pregnant women who used cannabis while pregnant, and leukemia in the offspring of pregnant women who used cannabis while pregnant. Groups at special risk not already mentioned include people with preexisting respiratory or heart conditions that might be provoked by cannabis use. Although our understanding of the effects of cannabis, for that matter most things, is subject to change, if not in the long term, at least in the short term, cannabis use on its own does not appear to have any major adverse effects in normal, healthy people which give due cause for alarm.
Mustafa