The Longterm Mental Health Risks Of Cannabis Use Biology Essay

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Cannabis is the most widely used illegal drug in Britain. Made from resin or dried leaves and flowers of the cannabis plant, it's a naturally occurring drug. It is a mild sedative (leading to effects of relaxation or sleepiness) and it's also a mild hallucinogen (leading to visual distortion of interpretation). The main active compound in cannabis is tetrahydrocannabinol (THC). The concentration of THC in strains developed over the last few years is said to be up to 5 times more potent compared to that of the cannabis available 30 years ago, Gruber, Pope, Hudson and Yurgelum-Todd (2003) which has been a great cause of concern for medical authorities and consequently governing bodies, which is one of the reasons for the reclassification of the drug to class B in January 2009.

A higher concentration of THC has thus brought further medical complications researched by scientists linking the recreational drug to CNS disorders such as depression and schizophrenia, which ultimately puts the user at risk between normal and psychotic operation of the central nervous system because of the use of cannabis.

What is Cannabis?

Cannabis sativa and cannabis indicia are widely known as members of the nettle family that have grown wild throughout the world for centuries but are cultivated today to produce specific strains of cannabis with increasing effects. Both plants have been used for a variety of purposes in the past including; hemp in the production of rope and textiles, as a medical herb and as the popular recreational drug.


The two main extracts of the plant which may be used as a drug include; The resin which is a brown/black lump, known by street names such as bhang, ganja, hashish, resin etc and Herbal cannabis which is made up of the dried flowering tops as well as a varying quantity of dried leaves which are known as grass, marijuana, spliff, weed etc.


The newer term 'Skunk', refers to a variety of stronger strains of cannabis available today, which have been cultivated to offer a higher concentration of the active substances and therefore the affects on the users including the changes on the users mental state. The name 'Skunk' given refers to the pungent smell which this form of cannabis expends whilst growing. They can be grown in the wild but also under grow-lights or in a greenhouse, often using hydroponic (growing in nutrient rich liquids rather than soil) techniques to evade the statues on the farming of this product (Polen, Sidney, Tekawa, Sadler and Friedman, 1993).

The concentration of the main psycho-active ingredient (THC) found in herbal cannabis varies from as low as 1% up to 15%, though the newer strains such as the bio technology enhanced skunk can have up to 20% making a stronger, potent drug that increases addictiveness. 

The newer varieties of Cannabis are, on average, two or three times stronger than those varieties available 30 years ago says who. What ever the potentencey of the drug the users will absorb the drugs through the smoke into the lungs then the bloodstream which rapidly. Cannabis will produce hallucinations with users with profound relaxation and elation alongside the negatives of nervousness, anxiety attacks, projectile vomiting and a strong desire to eat (Polen, Sidney, Tekawa, Sadler and Friedman, 1993. 


Thus unregulated illegal street cannabis has wide variety of strengths, disabling the users of the possibility to judge from looking at the Cannabis resin the exact strength of the active substances in any one particular purchase.

How does Cannabis work?

Cannabis is known to contain roughly 400 chemical compounds in an average plant. The four main compounds are known as delta-9-tetrahydrocannabinol (delta-9-THC), cannabidiol, delta-8-tetrahydrocannabinol (delta-8-THC) and cannabinol (Pope, Gruber, Hudson, Huestis and Yurgelum-Todd, 2001). Apart from cannabidiol (CBD), these compounds may induce psychoactive characteristics towards users, the strongest agent being delta-9-tetrahydrocannabinol. The stronger varieties of the plant contain minute levels of cannabidiol (CBD), substituted for a higher concentration of delta-9-THC (Pope, Gruber, Hudson, Huestis and Yurgelum-Todd, 2001)


When cannabis is inhaled through smoke, these compounds rapidly enter the bloodstream and are transported directly to the brain and other parts of the body. The feeling of being 'high' is caused mainly by the delta-9-THC binding to cannabinoid receptors found within the brain. A receptor is a site found on a cell where specific substances for that receptor can become bound to for a certain period of time. This leads to an effect on the cell and the nerve impulses it produces.

The cannabinoid receptors (CB2) are usually bound by naturally occurring substances known as endocannabinoids. When cannabis enters the bloodstream it binds to the CB2 receptors blocking the action of endocannabinoids on the occupied receptors (Herkenham, Lynn and Little, 1990)


Most of these receptors are found in the parts of the brain altering perceptions of pleasure, memory, thought, concentration, sensory and time perception.

Mental Health

Cannabis intoxication can cause distorted perceptions, impaired coordination, difficulty in thinking and problem solving, and problems with learning and memory. Research has shown that cannabis's adverse impact on mental processes and long term mental health including learning and memory which can last for days or weeks after the acute effects of the drug wear off (Gruber, Pope, Hudson and Yurgelum-Todd, 2003). As a result, someone who smokes cannabis every day may be functioning at a suboptimal intellectual level all of the time which affects long term mental health with conditions that cannot be reversed Gruber, Pope, Hudson and Yurgelum-Todd (2003).

Research on the long-term effects of cannabis abuse indicates some changes in the brain, and user's long term mental health and therefore relationship similar to those seen after long-term abuse of other major drugs. For example, cannabinoid 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.

Addictive Potential

Long-term cannabis abuse can lead to addiction; that is, compulsive drug seeking and abuse despite its known harmful effects upon physical health, mental health and social functioning and relationship in the context of family, school, work, and recreational activities (Rodriguez de Fonseca, Carrera and Navarro, 1997). Long-term marijuana abusers trying to quit the drug and return to a non drugs life style report irritability, sleeplessness, decreased appetite, anxiety, and drug craving, all of which make it difficult to control and remove the addiction. These withdrawal symptoms begin within about 1 day following abstinence, peak at 2-3 days, and subside within 1 or 2 weeks following drug cessation (Rodriguez de Fonseca, Carrera and Navarro, 1997).

Health Studies

A number of mental and physical health studies have shown an association between chronic marijuana use and increased rates of anxiety, depression, suicidal ideation, and schizophrenia. Some of these studies have shown age at first use to be a factor, where early use is a marker of vulnerability to later problems Gruber, Pope, Hudson and Yurgelum-Todd (2003). However, at this time, it is not clear whether marijuana use causes mental problems, exacerbates them, or is used in attempt to self-medicate symptoms already in existence.

Chronic marijuana use, especially in a very young person, may also be a marker of risk for mental illnesses, including addiction, stemming from genetic or environmental vulnerabilities, such as early exposure to stress or violence. At the present time, the strongest evidence links marijuana use and schizophrenia and/or related disorders. High doses of marijuana can produce an acute psychotic reaction; in addition, use of the drug may trigger the onset or relapse of schizophrenia in vulnerable individuals. Gruber, Pope, Hudson and Yurgelum-Todd (2003)

This had lead to increasing levels of evidence that people with serious mental illness, including depression and psychosis, are more likely to use cannabis or have used it for long periods of time in the past.  Regular use of the drug has appeared to double the risk of developing a psychotic episode or long-term schizophrenia.


Over the past few years, research has strongly suggested that there is a clear link between early cannabis use and later mental health problems in those with a genetic vulnerability which has stemmed from the issue of increasing use of cannabis by adolescents.



A study following 1600 Australian school-children, aged 14 to 15 for seven years, found that while children who use cannabis regularly have a significantly higher risk of depression, the opposite was not the case, children who already suffered from depression were not more likely than anyone else to use cannabis (Moore, Zammit, Lingford-Hughes, 2007). However, adolescents who used cannabis daily were five times more likely to develop depression and anxiety in later life.



Three major studies followed large numbers of people over several years, and showed that those people who use cannabis have a higher than average risk of developing schizophrenia. If you start smoking it before the age of 15, you are 4 times more likely to develop a psychotic disorder by the time you are 26 (Moore, Zammit, Lingford-Hughes, 2007). They found no evidence of self-medication. It seemed that, the more cannabis someone used, the more likely they were to develop symptoms.


Why should teenagers be particularly vulnerable to the use of cannabis? No one knows for certain, but it may be something to do with brain development. The brain is still developing in the teenage years - up to the age of around 20, in fact (Moore, Zammit, Lingford-Hughes, 2007).. A massive process of 'neural pruning' is going on. This is rather like streamlining a tangled jumble of circuits so they can work more effectively. Any experience, or substance, that affects this process has the potential to produce long-term psychological effects.


Recent research in Europe, and in the UK, has suggested that people who have a family background of mental illness - and so probably have a genetic vulnerability anyway - are more likely to develop schizophrenia if they use cannabis as well.  (Moore, Zammit, Lingford-Hughes, 2007).

Effects on the Heart

Cannabis increases heart rate by 20-100 percent shortly after smoking; this effect can last up to 3 hours. In one study, it was estimated that marijuana users have a 4.8-fold increase in the risk of heart attack in the first hour after smoking the drug.(Mittleman, Lewis, Maclure, Sherwood and Muller, 2001) This may be due to the increased heart rate as well as effects of cannabis on heart rhythms, causing palpitations and arrhythmias. This risk may be greater in aging populations or those with cardiac vulnerabilities.

Effects on the Lungs

Numerous studies have shown cannabis smoke to contain carcinogens and to be an irritant to the lungs. In fact, marijuana smoke contains 50-70 percent more carcinogenic hydrocarbons than does tobacco smoke (Mittleman, Lewis, Maclure, Sherwood and Muller, 2001). Cannabis users usually inhale more deeply and hold their breath longer than tobacco smokers do, which further increase the lungs' exposure to carcinogenic smoke. Marijuana smokers show dysregulated growth of epithelial cells in their lung tissue, which could lead to cancer; however, a recent case-controlled study found no positive associations between cannabis use and lung, upper respiratory, or upper digestive tract cancers(Tashkin, 2005). Thus, the link between marijuana smoking and these cancers remains unsubstantiated at this time.

Nonetheless, cannabis smokers can have many of the same respiratory problems as tobacco smokers, such as daily cough and phlegm production, more frequent acute chest illness, and a heightened risk of lung infections. A study of 450 individuals found that people who smoke cannabis 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 cannabis smokers in the study were for respiratory illnesses (Budney, Vandrey, Hughes, Thostenson and Bursac, 2008).

Cannabis psychosis

Recent research in Denmark suggests that yes, there is. It is a short-lived psychotic disorder that seems to be brought on by cannabis use but which subsides fairly quickly once the individual has stopped using it(Moore, Zammit, Lingford-Hughes, 2007).. It's quite unusual though - in the whole of Denmark they found only around 100 new cases per year.

 However, they also found that three quarters had a different psychotic disorder diagnosed within the next year and nearly half still had a psychotic disorder 3 years later.


So, it also seems probable that nearly half of those diagnosed as having cannabis psychosis are actually showing the first signs of a more long-lasting psychotic disorder, such as schizophrenia. It may be this group of people who are particularly vulnerable to the effects of cannabis, and so should probably avoid it in the future.

Cannabis addiction

It has some of the features of addictive drugs such as: tolerance - having to take more and more to get the same effect. Withdrawal symptoms: These have been shown in heavy users and include: Craving, decreased appetite, sleep difficulty, weight loss, aggression and/or anger, irritability, restlessness, strange dreams (Diana, Melis and Gessa, 1998).

These symptoms of withdrawal produce about the same amount of discomfort as withdrawing from tobacco.


For regular, long-term users:

3 out of 4 experience cravings;

half become irritable;

7 out of 10 switch to tobacco in an attempt to stay off cannabis.


The irritability, anxiety and problems with sleeping usually appear 10 hours after the last joint, and peak at around one week after the last use of the drug.



Research has provided evidence that Cannabis has potential to cause long terms effects. Those who are regular takers can suffer from physical, mental, social and cognitive abilities. Depending on the duration of smoking it that one may suffer serious health risks, however, in some cases this has been unsupported, but it is agreeable that there are more disadvantages in smoking Cannabis as opposed to it's advantages. Further research for this ongoing debate is beneficial that could support its long term effects as a priority to one's health.