Health effects of nicotine

Nicotine is an alkaloid found primarily in plants of the nightshade family, notably in tobacco; it is also synthesized.[1] Nicotine is used recreationally for its stimulant and anxiolytic effects.

In humans, nicotine acts primarily as a stimulant by binding to and activating nicotinic acetylcholine receptors (nAChRs) in the central nervous system and peripheral tissues. This results in the release of neurotransmitters such as dopamine, acetylcholine, and norepinephrine, producing effects including increased alertness, reduced anxiety, and mild euphoria.[2] Nicotine is typically consumed through tobacco smoking, vaping, or other nicotine delivery systems.

Effects on brain development

Main article: Effects of nicotine on human brain development

Exposure to nicotine, from conventional or electronic cigarettes during adolescence can impair the developing human brain.[3] E-cigarette use is recognized as a substantial threat to adolescent behavioral health.[4] Furthermore, youth and young adults are more vulnerable than adults to the long-term consequences of nicotine exposure, including susceptibility to nicotine addiction and potentially reduced impulse control, deficits in attention and cognition, and mood disorders.[4]

The use of tobacco products, no matter what type, is almost always started and established during adolescence when the developing brain is most vulnerable to nicotine addiction.[notes 1] Young people's brains build synapses faster than adult brains.[6] Because addiction is a form of learning, adolescents can get addicted more easily than adults.[6] The nicotine in e-cigarettes can also prime the adolescent brain for addiction to other drugs such as cocaine.[6]

Addiction to nicotine

Nicotine is addictive, and nicotine dependence is characterized by tolerance, physical dependence, psychological dependence, and nicotine withdrawal symptoms such as irritability, anxiety, and difficulty concentrating.[7][8]

According to studies by Henningfield and Benowitz, nicotine is more addictive than cannabis, caffeine, alcohol, cocaine, and heroin when considering both somatic and psychological dependence. However, due to the stronger withdrawal effects of alcohol, cocaine and heroin, nicotine may have a lower potential for somatic dependence than these substances.[9][10]

Although nicotine does play a role in acute episodes of some diseases (including stroke, impotence, and heart disease) by its stimulation of adrenaline release, which raises blood pressure,[11] heart and respiration rate, and free fatty acids, the most serious longer- term effects are more the result of the products of tobacco smoking. This has led to the development of various nicotine delivery systems, such as the nicotine patch or nicotine gum, that can satisfy the addictive craving by delivering nicotine without the harmful combustion by-products. This can help the heavily dependent smoker to quit gradually while discontinuing further damage to health.[12]

Nicotine in tobacco products

Main article: Health effects of tobacco

The health effects of nicotine also depend on its delivery methods, nicotine concentration on the product and accompanying compounds.

Smoking

When tobacco is smoked, most of the nicotine is pyrolyzed; a dose sufficient to cause mild somatic dependency and mild to strong psychological dependency remains. The amount of nicotine absorbed by the body from smoking depends on many factors, including the type of tobacco, whether the smoke is inhaled, and whether a filter is used. There is also a formation of harmane (a MAO inhibitor) from the acetaldehyde in cigarette smoke, which seems to play an important role in nicotine addiction[13] probably by facilitating dopamine release in the nucleus accumbens in response to nicotine stimuli.

Ingesting a compound by smoking is one of the most rapid and efficient methods of introducing it into the bloodstream, second only to injection, which allows for the rapid feedback which supports the smokers' ability to titrate their dosage. On average, it takes about ten seconds for the substance to reach the brain. As a result of the efficiency of this delivery system, many smokers feel as though they are unable to cease. Those who achieve one year of continuous abstinence are highly likely to remain so, with the vast majority of relapses occurring within the first eight days after attempting cessation.[14]

An average cigarette yields about 2 mg of absorbed nicotine, a dose sufficient to produce reinforcement and dependence while remaining far below toxic levels.[16]

Smokeless tobacco

Smokeless tobacco are tobacco products that is used by means other than smoking, for example by chewing, sniffing, or placing the product between gum and the cheek or lip.[17]

Smokeless tobacco differs depending on the type of product, the types of tobacco used, and the amount of each tobacco type used within a product. Each variable results in a different level of nicotine. Furthermore, nicotine is absorbed by the body to different degrees depending on the pH level of the product, which is known as the free nicotine or unionized nicotine level.[18]

The amounts of nicotine in saliva from using smokeless tobacco could be at amounts that can be toxic to cells in the oral cavity.[19]

Smokeless tobacco (including products where tobacco is chewed) is a cause of oral cancer, oesophagus cancer, and pancreas cancer.[20] Increased risk of oral cancer caused by smokeless tobacco is present in countries such as the United States but particularly prevalent in Southeast Asian countries where the use of smokeless tobacco is common.[21][22]

Nicotine replacement therapy

Nicotine replacement therapy (NRT) products, including gums, patches, and lozenges, deliver the compound in slower, lower doses that are less addictive and are used medically to help people quit smoking.[23][24]

Synthetic derivatives of nicotine, such as varenicline, act as partial agonists at nicotinic receptors and are also used as smoking cessation aids.[25]

See also

Notes

  1. ^ A 2018 review found "Nicotine is the third most commonly used substance by adolescents and use of electronic cigarettes has become twice as popular as traditional tobacco products. Concomitantly, e-cigarettes have been found to increase the risk for transitioning to more traditional tobacco cigarettes. Although acute administration of nicotine may enhance cognition in teens and young adults, especially memory and attention, chronic use has been linked with attention and working memory deficits in teens. Acute withdrawal from nicotine in adolescent users has also been associated with abnormal reward processing, working memory, and verbal memory fMRI tasks, highlighting the necessity to measure last use of nicotine prior to neurocognitive assessment."[5]

References

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  2. ^ Sajja RK, Rahman S, Cucullo L (March 2016). "Drugs of abuse and blood-brain barrier endothelial dysfunction: A focus on the role of oxidative stress". Journal of Cerebral Blood Flow and Metabolism. 36 (3): 539–554. doi:10.1177/0271678X15616978. PMC 4794105. PMID 26661236.
  3. ^ England LJ, Bunnell RE, Pechacek TF, Tong VT, McAfee TA (August 2015). "Nicotine and the Developing Human: A Neglected Element in the Electronic Cigarette Debate". American Journal of Preventive Medicine. 49 (2): 286–293. doi:10.1016/j.amepre.2015.01.015. PMC 4594223. PMID 25794473.
  4. ^ a b Stratton, Kathleen; Kwan, Leslie Y.; Eaton, David L. (January 2018). Stratton, Kathleen; Kwan, Leslie Y.; Eaton, David L. (eds.). Public Health Consequences of E-Cigarettes (PDF). National Academies of Sciences, Engineering, and Medicine (National Academies Press). pp. 1–774. Bibcode:2018nap..book24952N. doi:10.17226/24952. ISBN 978-0-309-46834-3. PMID 29894118.
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