THC's chemical structure is similar to the brain chemical anandamide. Similarity in structure allows the body to recognize THC and to alter normal brain. So how does marijuana have such a big impact on a person's ability to And after several decades of research they not only figured out how marijuana works, but discovered an important communications system in the brain and the body, . Because cannabinoid receptors are in so many parts of the brain and body, the effects But over time THC can change how the EC system works in these brain .
Does Body/Brain?: How Within the THC Work
This interferes with the ability of natural cannabinoids to do their job of fine-tuning communication between neurons, which can throw the entire system off balance. Because cannabinoid receptors are in so many parts of the brain and body, the effects of THC are wide-ranging: Refer to Figure 2 to see areas of the brain with cannabinoid receptors , then locate those areas on the chart to study some of the different effects of THC on the user.
Locations of Cannabinoid Receptors in the Brain. Breaking Down the Myths http: NIDA for Teens http: The Science of Marijuana: Department of Health and Human Services. Skip to main content. Find more facts about marijuana: Heads Up teacher site. But because of the ethical and logistical difficulties of conducting pain experiments on human volunteers, marijuana's potential to relieve pain has yet to be conclusively confirmed in the clinic.
Only a few such studies have been conducted and only one since Most tested the ability of cannabinoids to relieve chronic pain in people with cancer or acute pain following surgery or injury. Unfortunately, few of these studies are directly comparable because the methods used to conduct them varied greatly and in some cases appear to have been less than scientifically sound.
However, after critically reviewing existing research on THC and pain relief, the IOM team concluded that cannabinoids can provide mild to moderate relief from pain, on a par with codeine.
The IOM team also determined that the body 's own cannabinoid system likely plays a natural role in pain control. By contrast, some clinical studies not only have failed to demonstrate that THC relieves pain but have also found that the drug has the opposite effect. In these experiments, volunteers who experienced painful shocks, heat, or pressure from a tourniquet reported that THC actually increased their sensitivity to pain.
Participants were exposed to shocks or pressure over a range of intensities but were only asked to note when they first felt pain and the maximum intensity of pain they could withstand.
Since most people take medication for moderate pain, it would have been more useful to evaluate the ability of THC to relieve pain between the extremes that were actually measured researchers commonly do this by asking participants to use a. The second problem with this study is that the researchers failed to demonstrate that other painkillers could work under their experimental conditions. Without this standard of comparison, the results on THC have little meaning.
They may conflict with those of other studies simply because of the methods the researchers used. Design flaws also compromise a study that tested smoked marijuana 's ability to relieve heat-induced pain in human volunteers. In this experiment, habitual marijuana users were hospitalized and allowed free access to marijuana cigarettes for a period of four weeks. During this time, volunteers consumed an average of four to 17 marijuana cigarettes per day and were tested periodically to gauge their response to painful heat applied to the skin.
It is therefore not surprising that THC failed to relieve pain under these conditions. Two studies have examined the effectiveness of THC and levonantradol, a synthetic compound similar to THC, in relieving acute postoperative pain. In the first, volunteers who each had four molars extracted on separate occasions received the local anesthetic lidocaine plus one of the following treatments, given intravenously, with each successive tooth extraction: Twenty-four hours after surgery the patients were asked to rate how much pain they felt during the procedure.
Based on these ratings the researchers concluded that THC had no effect on surgical pain. There are several reasons to question this conclusion, however.
Most importantly, the scientists once again failed to check whether another pain reliever, rather than a sedative, would have fared better than THC in the test. Lidocaine almost certainly diminished the patients' perceptions of pain, which were further compromised because they were not reported until 24 hours after surgery.
The study on levonantradol is less problematic. Researchers gave the drug by intramuscular injection to 56 volunteers 24 to 36 hours after they were treated for injuries or underwent surgery. To eliminate the possibility that prior drug exposure would influence the patients' experience, the researchers did not test people who had a history of drug abuse or addiction or those who were taking prescription drugs that might interfere with their ability to perceive pain.
On average, the researchers reported, patients who received levonantradol after surgery experienced significantly greater pain relief than those who got the placebo. The extent to which patients varied in their response to the drug is not clear, however. The authors do not reveal whether all patients who took the THC analog felt its effects to some extent or whether some people obtained great relief while others found it had little or no effect on their postoperative pain.
The most encouraging—and believable—clinical studies of cannabinoids focus on chronic pain in cancer patients. Cancer causes pain in a variety of ways, including inflammation, nerve injury, and the invasion of bone and other sensitive tissue by growing tumors. Cancer pain tends to be severe, persistent, and resistant to treatment with opiate painkillers.
For this reason, researchers hope to discover pain relievers that act on the body in a different way than opiates do. In one such study, 10 patients with advanced cancer received THC pills in four different doses as well as a placebo.
Each patient received the entire range of pills, which were identical in appearance, over successive days. On days when patients received the two highest doses—15 and 20 milligrams of the drug, as compared with 0, 5, or 10 milligrams—they reported significant pain relief.
By comparison, when patients take Marinol for AIDS wasting, an approved indication, they commonly take it in 5-milligram doses, with a maximum dosage of 20 milligrams per day.
Marijuana cigarettes contain highly variable amounts of THC, typically between 30 and milligrams, but much of that THC is lost in uninhaled smoke. The study did not, unfortunately, compare THC with any other painkiller. Although they reported feeling less pain, patients who received the highest dose of THC in this study were also heavily sedated. They appeared dreamy and immobile; their thoughts were disorganized and they described feelings of unreality.
Moreover, during the process of selecting patients to participate in the study, five of 36 volunteers became intensely anxious after receiv-. If this experiment is any indication, THC's side effects—though somewhat different—are as problematic as those of opiates. Interestingly, during this study none of the patients experienced nausea or vomiting and more than half reported that their appetite increased, which suggests that oral THC acted as an antiemetic and an appetite stimulant, as well as a pain reliever.
The authors also noted that some patients who appeared calmer after taking THC reported that it had not relieved their pain; other patients said that while their pain remained the same it bothered them less. These impressions resemble several anecdotal reports from marijuana users, who told the IOM team that marijuana did not take away their pain but helped them cope with their discomfort.
In a subsequent study the same researchers compared the effects of a single potent dose of THC with that of a relatively weak narcotic pain reliever, codeine. They found that 10 milligrams of THC gave the same pain relief as a milligram moderately strong dose of codeine and that 20 milligrams of THC worked as well as milligrams of codeine. The two drugs produced similar side effects, but THC appeared to be more sedating than codeine. On the other hand, patients tended to have a greater sense of well-being and less anxiety after taking THC than they did under the influence of codeine.
Another group of researchers compared two conventional painkillers, codeine and secobarbital a short-acting barbiturate , with a synthetic compound similar to THC. This THC analog had previously been shown to block pain in animals, so it was being tested for its ability to relieve moderate to severe pain in cancer patients.
Both comparisons were conducted in cancer patients who suffered moderate to severe pain. In one trial 30 such patients were given three different treatments, in random order, on consecutive days: Patients then rated the intensity of their pain on a three-point scale none, slight, moderate every hour for six hours.
The second trial, which compared the cannabinoid with secobarbital in 15 patients, followed the same procedure. On average, participants found that. In addition to the clinical trials already discussed, a handful of case studies and surveys have addressed the ability of marijuana or cannabinoids to relieve pain.
The case studies are generally unconvincing, but survey responses suggest that marijuana—and by extension cannabinoids —can ease certain chronic pain syndromes. For example, in a recent survey of more than regular marijuana users with multiple sclerosis, nearly every participant reported that marijuana helped relieve spasticity and limb pain see Chapter 7.
Yet the IOM team located only one scientific report on that subject published since It consists of a description of three cases in which people suffered migraines after quitting their daily marijuana habits. Exploring the possibility of using marijuana-based medicines to relieve migraine pain will require rigorous clinical experiments designed to control for factors that can bias the results. A possible link between cannabinoids and migraine has been revealed, however, in studies of cannabinoid receptors in the brain.
These receptors occur in abundance in the periaqueductal gray PAG region, an area where migraines are suspected to arise. But it remains to be determined what effect cannabinoids exert on the PAG and whether they might prevent migraines from occurring.
Such research would be worth doing since the best medicine currently available for migraines, sumatriptan Imitrex , fails to provide complete relief for more than one in four of the patients who use it.
An estimated 11 million people in the United States suffer from moderate to severe migraines. Much of what medical scientists have learned about marijuana's pain-relieving potential warrants further study, according to the IOM team. A logical next step in basic research. But some of those side effects may make marijuana an especially useful pain reliever.
Cannabinoids appear to reduce nausea, vomiting, and appetite loss as well as pain. And the euphoric lift that attracts recreational users to marijuana could benefit people with anxiety-producing disorders such as AIDS or cancer.
In fact, for that reason the IOM team recommended that researchers undertake clinical studies of cannabinoid medications among cancer patients on chemotherapy and AIDS patients suffering from wasting or significant pain. The IOM also recommended that the following groups of patients be included in such studies:. In this case, cannabinoids should be administered along with opiates to determine whether cannabinoids reduce the nausea and vomiting associated with opiate painkillers. All of the above patients are currently treated with opiate drugs, which produce tolerance and dependence as well as undesirable side effects.
Could lower doses of opiates give these patients the same degree of relief when supplemented with cannabinoids? The answer lies in carefully conducted clinical experiments. Clinical trials could also determine whether THC is the sole—and, if not, the best —pain-relieving compound in marijuana. If additional cannabinoids relieve pain, researchers must then consider which cannabinoids or combinations thereof work best.
Although there has been very little clinical pain research on marijuana, the findings support positive results from animal and other basic experiments. Further clinical research appears to be well worth pursuing if it leads to a new class of drugs to complement existing painkillers or medications that could simultaneously relieve pain and nausea or appetite loss.
Looking for other ways to read this?
After you inhale marijuana smoke, its chemicals zip throughout the body. THC is a very potent chemical compared to other psychoactive drugs. Once in your. Foundational understanding is lacking, and while there is a growing body of research looking at various aspects of cannabis effect, as is always. How Does THC Work Within the Body/Brain?: Each individual has an important and necessary system within their body, known as the.