View source for Harm Reduction: Cannabis effects and risks

As with any other substance, the effects of cannabis are determined by various factors. In principle, it is necessary to consider the type of product (such as hashish, resin, oil, or marijuana), the administered dose, and the route of administration (whether smoked or oral), as well as the characteristics of the person (such as previous experience with the substance and personality traits) and the environment and circumstances in which it is used.

== Cannabinoids ==
The plant's cannabinoids are responsible for its psychoactive effects. <br>
• <strong>Delta-9-tetrahydrocannabinol (Δ9-THC).</strong> is the main psychoactive cannabinoid responsible for most of the biological effects  <br>
• <strong>Cannabidiol (CBD)</strong> attenuates the psychoactive effects of THC and has its own biological effects.  <br>
• <strong>Cannabinol (CBN)</strong> is a product of THC degradation, which indicates the age of a sample.  <br>
• <strong>Cannabichromene (CBC)</strong> may have a sedative effect <br>
• <strong>Tetrahydrocannabivarin (THCV)</strong> may have a metabolic effect on diabetes and obesity.  <br>
• <strong>Cannabigerol (CBG)</strong> has an antibiotic/defensive effect in the plant. <br>

== General effects ==
The effects that can occur after the administration of cannabis are extraordinarily varied. Generally, there is a change in the usual state of consciousness, which alters the way in which one perceives oneself and the surrounding environment, as well as the usual way in which thoughts and language are handled and processed. In this sense, although cannabis is sometimes classified as a nervous system depressant (along with alcohol and benzodiazepines), its effects are closer to those of psychedelics or visionary substances (hallucinogens), although much more moderate in intensity. Like psychedelics, cannabis has a touch of unpredictability: the same substance on the same person can produce very different effects on different occasions.

The psychological effects of smoked cannabis begin within minutes and last for the next 3-4 hours. This fact allows better control of the amount that the user administers and reduces the possibility of overdosing. The effects by oral route (generally marijuana in cookies or salads) begin later and usually have greater intensity and duration,facilitating the appearance of adverse reactions, particularly in people with little experience with the substance or those who are susceptible to this type of reaction.

A feeling of placidity and well-being usually appears, which may be accompanied by extreme hilarity (anything seems extraordinarily funny and makes one laugh) or by introspection and contemplative silence. A general sharpening and moderate increase in the awareness of the senses (sight, taste, touch...) is characteristic. The sense of time can be distorted. While seeing geometric patterns with eyes closed is rare, it is possible, especially with more powerful varieties.

In most cases, and considering the factors already mentioned, the pleasant effects of cannabis predominate over the neutral or unpleasant ones. However, it should be noted that for certain types of people, this range of effects can be uncomfortable or unpleasant, leading to states of anxiety or anguish of varying intensity and duration. This fact is also frequent in people who consume cannabis for the first time and who are not used to its effects.

=== Organical effects and risks ===
==== Animal studies vs human studies ====
When assessing other possible physical risks of cannabis, it is important to be careful to differentiate between effects observed in experimental animals, where very high and/or very frequent doses of cannabis are generally administered orally or intravenously under laboratory conditions, and effects demonstrated in humans. In rats and monkeys, alterations in the concentration of sex hormones have been found when they have been subjected to very intensive regimens of cannabis administration. However, there is no objective scientific data to indicate that these alterations in animals can be extrapolated to humans or that any conclusions can be drawn from this fact. In fact, at least two studies in humans have found no differences in the sex hormone levels of cannabis users and non-users. Furthermore, there are no epidemiological studies linking cannabis use with infertility, chromosomal damage, or genetic damage in humans.

==== Toxicity potential. ====
At the physical level cannabis is characterized by an extraordinarily low acute toxicity; the consequences of an overdose can be remarkable in terms of psychological effects but the probability of death or serious physical sequelae after cannabis intoxication is almost nil. However, like any substance, it is not free of physical risks that should be known.

==== Cardiovascular and metabolic effects ====
Dry mouth and a characteristic reddening of the conjunctiva of the eye due to dilation of the blood vessels usually appear. This same mechanism at the level of the large arteries of the body can lead to drops in blood pressure (orthostatic hypotension) that are compensated by the body by making the heart beat faster (reflex tachycardia). Dizziness or loss of consciousness that appear in inexperienced users or those who have consumed large amounts of cannabis are not caused by drops in blood glucose (as is sometimes mistakenly claimed) but by decreases in blood pressure. The increased work of the heart may have consequences in people with severe cardiovascular disease but is generally well tolerated by healthy individuals. Strokes are also possible, although very rare. 

==== Respiratory effects ====
The fact that cannabis derivatives are commonly smoked with tobacco makes it difficult to know what risks are attributable to either substance. The combustion of cannabis produces irritant and carcinogenic products, and it is reasonable to assume that chronic inhalation of such compounds may have long-term consequences similar to those of tobacco, such as chronic bronchitis and lung cancer. Studying this question is difficult, as there are few smokers who use only unmixed cannabis derivatives, and the total amounts smoked are generally lower than those of tobacco smokers.

The use of vaporizers diminish respiratory risks derived from combustion. There are some homologued vaporizers that have proved to achieve adequate levels of cannabinoids in organism avoiding harmful particles. These devices are used in clinical trials with therapeuric cannabis

==== Neurocognitive (memory) effects ====
Studies on the endogenous cannabinoid system in humans suggest that it is involved in memory, learning, and attention processes. Thus, it seems logical to think that the administration of cannabinoids may have some effect on these functions.

Cannabis use has been associated with alterations in immediate and recent memory, which are the ability to learn and recall new information, as well as in executive brain functions requiring complex manipulations of learned material.

No relationship has been found between cannabis use and disturbances in remote memory, which is the ability to recall old memories.

However, when assessing these effects, it is important to distinguish between those that appear while smoking or in the following hours (acute) and those that appear when assessing the memory of regular cannabis smokers.

People who are under the effects of cannabis make more errors or achieve lower scores in psychological tests that measure some functions related to recent memory and attention, as well as in certain psychomotor skills. In people who use cannabis occasionally or sporadically, these alterations are maintained only during the time in which the state of cannabis intoxication persists, returning the functions to normal once the active compounds have been eliminated from the organism.

Individuals who use cannabis daily and habitually can reach a state in which their organism is constantly under the effects of the substance. Depending on the frequency of use, intensity, and personal characteristics, some people may present chronic alterations in memory as a reflection of the constant action of cannabinoids on the organism.

However, this effect does not imply toxicity, such as chronic or irreversible damage, as the alterations normalize within a few weeks after stopping cannabis consumption. Scientific studies have shown that there are no differences in memory between people who have never smoked cannabis and those who have not smoked for a month.

==== Cannabis Hyperemesis Syndrome ====
A recently described entity, in 2017, is the Cannabis Hyperemesis Syndrome . Although the finding of a specific syndrome in a substance with more than three thousand years of history of human consumption is striking, the syndrome seems to have a specific entity. The number of cases is limited, but showing an increasing tendence on time. It is probably linked to high potency cannabis.

Essential criteria

Cannabis use for more than 5-10 years

Major criteria: <br>
• Frequent and severe nausea and vomiting of cyclic nature <br>
• Pattern of marijuana use at least 1-2 times per week <br>
• Abdominal, epigastric or umbilical pain <br>
• Relief of symptoms with hot baths or showers <br>

Minor criteria Age < 50 years

Weight loss > 5 kg  <br>
Morning predominance of symptoms <br>
Normal medical examinations <br>

=== Mental health ===
====  Cannabis and psychosis ====
The most extensively studied relationship is the one between cannabis and psychosis.<br>
The following data is considered to be the most relevant:<br>

Frequent anxiety disorders appear as acute adverse effects of cannabis use. Acute self-limited toxic psychosis can also occur in predisposed individuals, especially those with low tolerance and/or high doses, using very potent strains, or via the oral route.

The presence of psychotic symptoms during acute cannabis intoxication is considered a risk factor for developing chronic psychotic disorders in the future. In those who have had this complication and continue using cannabis, the long-term diagnosis of chronic psychotic disorder is more common.

Cannabis use in patients already diagnosed with schizophrenia worsens symptoms, increases hospitalizations, and has a worse prognosis.

The relationship between cannabis use and the development of chronic psychotic disorders is still debated. The accepted model explains schizophrenia as a result of a series of risk factors on a vulnerable personality due to genetic and/or environmental reasons. In this sense, cannabis use can be considered a stressful risk factor (like parental separation, a breakup, or military service). However, the existence of a "cannabis psychosis" in which cannabis use is a necessary and sufficient factor is not supported by available scientific evidence 

==== Cannabis and Amotivational Syndrome ====
Some scientists argue that heavy cannabis use can lead to a condition called amotivational syndrome. It is characterized by apathy, indifference, loss of self-improvement spirit, and lack of interest in studies, resulting in a change in lifestyle where conventional ambitions and motivations are lost. It is challenging to distinguish whether the relationship between cannabis use and this syndrome is one of cause, consequence, or association.

Many cases coincide with adolescence or early youth, which is a time of significant personality changes. Adolescence itself has something of an "amotivational" character in many cases. No mechanism has been proposed for how the syndrome occurs, nor is there any consensus on diagnostic criteria, evolution, or possible treatments. Professional diagnostic manuals (DSM-V and ICD-10) also do not include this syndrome.

Therefore, although certain patterns of cannabis consumption may affect individual personalities, amotivational syndrome cannot be considered from a strictly scientific point of view.
=== Effects on pregnancy, fetus and newborn ===
The most relevant data are: <br>
• Children born to cannabis users have been found to have a lower birth weight. Tobacco use could be a potential confounding factor in this respect. <br>
• Mild neurocognitive deficits have also been reported (only noticeable in specific tests) that are maintained up to two years after birth <br>
• There is no evidence of teratogenic potential of cannabis in humans. <br>
• Immunological alterations have also been found in specific blood tests of unknown significance <br>

In general, the data from the available studies are questionable in their methodology and, at times, adventurous in their conclusions. For example, studies linking marijuana use to the development of childhood tumors are seriously flawed

In practice, the amount of cannabinoids to which the fetus is exposed in mothers who use marijuana and their repercussions are unknown. It is clear that cannabinoids are very liposoluble molecules (they cross biological membranes well) and that cannabinoid receptors are expressed in tissues such as the Central Nervous System and the Immune System.

On the other hand, it has been demonstrated that the development of the endogenous cannabinoid system occurs mainly after birth.
In any case, common sense indicates that during pregnancy only those drugs that are essential and medically indicated should be used. The use of cannabis during pregnancy should be considered contraindicated. In practice, some women find it difficult to achieve this goal, which requires an individualized approach, always from an empathetic attitude and avoiding moral judgments.
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