Scientists have known for a long time that THC interacted with cannabinoid receptors in the brain, but did not know why the brain would have such receptors. They thought that the brain must make some kind of substance that naturally acted on these receptors. In 1992, they found the answer...anandamide. Anandamide is the brain's own THC (just like "endorphin" is the brain's own morphine). Still, scientists are not sure what the function of anandamide is in the normal brain. The effects of marijuana start as soon as 1-10 minutes after it is taken and can last for 3-4 hours. There is some evidence that the effects of marijuana may last even longer. Experiments have shown that THC can affect two neurotransmitters: norepinephrine and dopamine. Serotonin and GABA levels may also be altered.

It is controversial whether marijuana causes long-term mental abnormalities. Only future research will give us the answers. It is interesting to note that there are NO documented cases of a fatal overdose produced by marijuana. However, because there is a high level of tar and other chemicals in marijuana, smoking it is similar to smoking cigarettes. The lungs get a big dose of chemicals that increase the chances of lung problems and cancer later in life.

The Effects of Marijuana on the Brain

Scientists have learned a great deal about how THC acts in the brain to produce its many effects. When someone smokes marijuana, THC rapidly passes from the lungs into the bloodstream, which carries the chemical to organs throughout the body, including the brain.

In the brain, THC connects to specific sites called cannabinoid receptors on nerve cells and influences the activity of those cells. Some brain areas have many cannabinoid receptors; others have few or none. Many cannabinoid receptors are found in the parts of the brain that influence pleasure, memory, thought, concentration, sensory and time perception, and coordinated movement.

The short-term effects of marijuana use can include problems with memory and learning; distorted perception; difficulty in thinking and problem solving; loss of coordination; and increased heart rate. Research findings for long-term marijuana use indicate some changes in the brain similar to those seen after long-term use of other major drugs of abuse. For example, cannabinoid (THC or synthetic forms of THC) withdrawal in chronically exposed animals leads to an increase in the activation of the stress-response system and changes in the activity of nerve cells containing dopamine. Dopamine neurons are involved in the regulation of motivation and reward, and are directly or indirectly affected by all drugs of abuse.

The Effects of Marijuana on the Heart

One study has indicated that a user’s risk of heart attack more than quadruples in the first hour after smoking marijuana. The researchers suggest that such an effect might occur from marijuana’s effects on blood pressure and heart rate and reduced oxygen-carrying capacity of blood.

The Effects of Marijuana on the Lungs

A study of 450 individuals found that people who smoke marijuana frequently but do not smoke tobacco have more health problems and miss more days of work than nonsmokers. Many of the extra sick days among the marijuana smokers in the study were for respiratory illnesses.

Even infrequent use can cause burning and stinging of the mouth and throat, often accompanied by a heavy cough. Someone who smokes marijuana regularly may have many of the same respiratory problems that tobacco smokers do, such as daily cough and phlegm production, more frequent acute chest illness, a heightened risk of lung infections, and a greater tendency to obstructed airways.

Cancer of the respiratory tract and lungs may also be promoted by marijuana smoke. A study comparing 173 cancer patients and 176 healthy individuals produced strong evidence that smoking marijuana increases the likelihood of developing cancer of the head or neck, and the more marijuana smoked the greater the increase. A statistical analysis of the data suggested that marijuana smoking doubled or tripled the risk of these cancers.

Marijuana use has the potential to promote cancer of the lungs and other parts of the respiratory tract because it contains irritants and carcinogens. In fact, marijuana smoke contains 50 to 70 percent more carcinogenic hydrocarbons than does tobacco smoke. It also produces high levels of an enzyme that converts certain hydrocarbons into their carcinogenic form—levels that may accelerate the changes that ultimately produce malignant cells. Marijuana users usually inhale more deeply and hold their breath longer than tobacco smokers do, which increases the lungs’ exposure to carcinogenic smoke. These facts suggest that, puff for puff, smoking marijuana may increase the risk of cancer more than smoking tobacco.

Other Health Effects of Marijuana

Some of marijuana's adverse health effects may occur because THC impairs the immune system’s ability to fight off infectious diseases and cancer. In laboratory experiments that exposed animal and human cells to THC or other marijuana ingredients, the normal disease-preventing reactions of many of the key types of immune cells were inhibited. In other studies, mice exposed to THC or related substances were more likely than unexposed mice to develop bacterial infections and tumors.

In Low to Medium Doses The Effects of Marijuana are:

In high doses, the Effects of Marijuana are:

The effects of marijuana will vary from person to person depending on:

Short-term effects of using marijuana include:

Long-term effects of using marijuana include: