Quote:
Originally Posted by maverick030581 Man.I've been smoking for the last 8 years and it is without a doubt the most addictive habit anyone can ever have.My advice to anyone who hasn't started : Don't ever even think of starting.A totally harmful habit but one that seems impossible for me to quit. |
From a study done by our organisation (all publicly available data and research):
Dr. Jack E. Henningfield of the US National Institute on Drug Abuse, and Dr. Neal L. Benowitz of the University of California at San Francisco ranked six substances (nicotine, heroin, cocaine, alcohol, coffee, and marijuana) on five areas: (a) withdrawal: presence and severity of characteristic withdrawal symptoms; (b) reinforcement: a measure of the substance's ability, in human and animal tests, to get users to take it again and again, and in preference to other substances; (c) tolerance: how much of the substance is needed to satisfy increasing cravings for it, and the level of stable need that is eventually reached; (d) dependence: how difficult it is for the user to quit, the relapse rate, the percentage of people who eventually become dependent, the rating users give their own need for the substance and the degree to which the substance will be used in the face of evidence that it causes harm, and (e) intoxication: though not usually counted as a measure of addiction in itself, the level of intoxication is associated with addiction and increases the personal and social damage a substance may do. Their findings indicate that nicotine ranked the highest in dependence, and the second-highest on tolerance.
Amongst new smokers, inhaling smoke from only 1 or 2 cigarettes is sufficient to induce craving, the most common symptom of dependence. Around 10% of new users lose autonomy over tobacco and become dependent within 2 days of inhaling from a cigarette for the first time. Nearly 50% lose autonomy by the time they were smoking only 7 cigarettes per month. Thus, it may take only 1 cigarette to initiate a life-long dependence on tobacco.
Nicotine, when inhaled, enters the lungs where a large surface area of small airways and alveoli exists. Nicotine undergoes dissolution in pulmonary fluid, is transported to the heart, and then immediately passes to the brain. The rapid rate of nicotine absorption and high amounts of nicotine attained in the brain from smoking and tobacco use are two crucial factors that promote and sustain nicotine addiction. Nicotine affects many neurotransmitter systems in the brain: dopamine, norepinephrine, acetylcholine, serotonin, γ-aminobutyric acid, glutamate, and endorphins. The major effect of nicotine is to stimulate release of these transmitters. Of primary importance to its addictive nature are findings that nicotine activates the brain circuitry that regulates feelings of pleasure, the so-called reward pathways. A key brain chemical involved in mediating the desire to consume drugs is the neurotransmitter dopamine, and nicotine indirectly causes a release of dopamine in the brain regions that control pleasure and motivation. Because dopamine release signals a
pleasurable experience, the effect of nicotine on dopamine release is critical to the reinforcing effects of nicotine. This reaction is similar to that seen with other drugs of abuse, such as cocaine and heroin, and is thought to underlie the pleasurable sensations experienced by many tobacco users.
Nicotine can act as both a stimulant and a sedative. Immediately after exposure to nicotine, there is a `kick’ caused by nicotine’s stimulation of the adrenal glands and resulting discharge of epinephrine (adrenaline). The rush of adrenaline stimulates the body and causes a sudden release of glucose as well as an increase in blood pressure, respiration, and heart rate. Cigarette smoking produces a rapid distribution of nicotine to the brain, with drug levels peaking within 10 seconds of inhalation.
Nicotine dosage is carefully controlled by manufacturers to ensure that nicotine dose levels are sufficient for target populations to produce desired effects such as relaxation and mental acuity, while minimising the risk of producing undesirable effects such as nausea and intoxication. Acetaldehyde used in cigarettes is a known carcinogen that also potentiates the dependence-causing effects of nicotine. Further, nearly 20% of the documented cigarette additives have pharmacological actions that camouflage the odour of environmental tobacco smoke emitted from cigarettes, enhance or maintain nicotine delivery, could increase the addictiveness of cigarettes, and mask symptoms and illnesses associated with smoking behaviours. Certain additives such as menthol in manufactured cigarettes are added specifically to reduce the smoke harshness and enable the smoker to take in more dependence-causing and toxic substances. Higher rate of absorption can also influence the dependence-causing and reinforcing effects. For example, among tobacco products, cigarettes (and variants such as bidis, kreteks or waterpipes) are associated with the highest levels of disease among tobacco products because their designs and ingredients both facilitate and reinforce powerful dependencies and deep lung exposure of toxins. They deliver mildly acidic smoke that is inhaled more easily than the alkaline smoke of most pipes and cigars. The rapid absorption of nicotine (from smoking) in the lung has a high potential to cause dependence because it very rapidly results in delivery of small doses to the brain, establishing the repetitive and persistent smoke self-administration characteristic of smokers of cigarettes and other smoking products.
As would be expected with substances associated with tolerance and addictive properties, with chronic or even acute administration of nicotine, neural adaptations occur. Neural receptors also become desensitised or inactivated, which is one potential mechanism leading to the development of tolerance. This means that more nicotine is required to deliver the same neurochemical effect. Although independent of nicotine effects, cigarette smoking is associated with decreased activity of monoamine oxidase enzymes in the brain, which are associated with the degradation of dopamine. Inhibition of monoamine oxidase activity augment nicotine effects of increasing dopamine levels and contribute to positive reinforcement, tolerance, and addiction. Thus the effects of nicotine dissipate in a few minutes, causing the tobacco user to continue dosing frequently throughout the day to maintain the drug's pleasurable effects and prevent withdrawal. Nicotine also creates tolerance. There is rapid development of tolerance to subjective effects such as pleasure. In the long term, nicotine depresses the ability of the brain to experience pleasure. Thus, tobacco users may need greater amounts to achieve the same levels of satisfaction. Such escalating usage may be observed for several years after initiation of tobacco use.
Thus nicotine addiction is thus sustained by a combination of positive effects of nicotine on neurotransmitter levels related to pleasure and arousal, the dampening effect of those pleasure or reward mechanisms over time, and the need for continued nicotine exposure to avoid the negative affects related to the decreased neurotransmitter levels, particularly that of dopamine, that would occur without nicotine. However, in addition to the pharmacologic mechanisms of nicotine, conditioning is thought also to play an important role in tobacco. With regular tobacco use, specific moods or other environmental factors, known as `cues’ or stimuli, become associated with the pleasurable or rewarding effects nicotine. With time and associative learning, these stimuli begin to control behaviour, such that when a smoker is exposed to these stimuli, they evoke craving. This association between the cues and the anticipated pleasure associated with the drug, known as conditioning, is a powerful contributor to addiction known as conditioning. Smoking and tobacco use is also maintained in part by conditioning. For example, smoking becomes associated with specific behaviours, such as drinking a cup of tea/coffee or alcohol. Repetition of these co-existing behaviours over time leads to the behaviour becoming a cue the person to want to smoke. Behaviours can be conditioned to either the positive or negative reinforcing effects of nicotine. For example, because smoking becomes associated with relieving the negative effects of nicotine withdrawal, the smoker can associate smoking with relieving other negative feelings, such as stress.