Addiction Annulled: A Brief Background on Cigarette Cessation
Tobacco use is widely considered to cause more preventable and premature deaths than any other factor in developed countries. In other words, a successful campaign against tobacco use would arguably save more lives globally than any other campaign for public health.
There are many different ways of consuming tobacco, but for the purposes of this paper only cigarette smoking will be discussed and will be referred to simply as “smoking.” It is well known that smoking causes a variety of serious negative health effects; all one has to do is look at the warning label on a box of cigarettes. Why then, in spite of the obvious dangers, do so many people continue to smoke? One reason is simply because smoking looks cool, mainly due to its glorification in popular culture. In a more recent phenomenon, it seems that lower numbers of smokers in the population have given smoking a unique, hipster image. While an important one, image is not the only factor preserving smoking’s popularity; the main factor can only be fully understood through neuroscience. It is a specific process occurring within the brain called addiction, or more technically drug dependence.
The chemical compound nicotine is the main psychoactive ingredient in tobacco that enters the brain rapidly after smoking. Nicotine acts upon nicotinic acetylcholine receptors. When a nicotine molecule binds to its receptor it can have a variety of effects depending on the receptor type, the location of the receptor within the neuron, and the location of the neuron within the brain. Most commonly nicotine enhances neurotransmitter release; an effect that is affiliated with the stimulant class of drugs. While nicotine has been shown to enhance the release of all known neurotransmitters, the specific neurotransmitter associated with smoking addiction is called dopamine.
One general function of dopamine in the brain is to provide reinforcing feedback to reward certain behaviors. Nicotine’s activation of dopamine-releasing neurons can be associated with pleasant feelings, or alleviation of unpleasant ones (such as craving a cigarette), and is thought to be the primary neurological mechanism for smoking addiction. Naturally, dopamine rewards behaviors necessary for life such as eating and sex; when activated by nicotine it specifically rewards one thing: self-administration of more nicotine. Habitual smokers who abstain from smoking for too long experience withdrawal symptoms such as irritability and headache, but mostly their minds are focused on one thing: smoking another cigarette. This strong urge to smoke again is called craving, and is a major affliction of anyone with drug dependence. A common way to subdue cravings for people trying to quit or cut down on smoking is through use of a nicotine patch that delivers nicotine through the skin. While these patches do activate dopamine reward pathways in the brain and reduce cravings, they are not particularly effective at getting people to quit. In a controlled study done in New Zealand only 5.8% of participants were able to quit smoking using a nicotine patch. Another, more recent way to subdue cravings is the electronic cigarette. Like the nicotine patch it delivers nicotine to the brain and dopamine reward pathways to reduce cravings. What makes the electronic cigarette different is its appearance. At a distance someone using an electronic cigarette is indistinguishable from someone smoking. The way electronic cigarettes look might seem trivial, but, as mentioned earlier, image can play an important factor and is sometimes what gets people to start smoking in the first place. In the same New Zealand study, 7.3% of participants using electronic cigarettes achieved abstinence from smoking, making electronic cigarettes almost 30% more effective than nicotine patches. The most surprising results, however, came from participants using placebo electronic cigarettes that contained no nicotine. Despite lacking nicotine induced activation of dopamine reward pathways in their brains, 4.1% of participants using the placebos were able to obtain abstinence, making simply the act of using an electronic cigarette 70% as effective as nicotine patches for obtaining abstinence in the study.
How is it possible that a device containing no nicotine was able to satisfy users suffering from nicotine-withdrawal induced cravings? The answer may be found in a function of the brain known as parallel processing. Simply put, parallel processing describes the simultaneous activation of multiple brain pathways. When a person smokes, not only is his or her brain receiving nicotine, but also sensory information associated with smoking: the feeling of pulling air through the cigarette, the smell and taste, seeing the smoke while exhaling, and other sensory responses that might not even be consciously interpreted. One important pathway in the brain is from the olfactory bulb directly to the Ventral Tegmental Area, located near the top of the brainstem, which produces dopamine. Thus, simply smelling a cigarette or (because taste and olfaction are so closely connected) tasting something associated with smoking can trigger cravings. For example, someone who has previously drank coffee while smoking cigarettes (a popular combination) will suddenly crave a cigarette when he or she drinks coffee, or even gets a whiff of it. Because all of the sensory information associated with smoking is also associated with a nicotine induced reward response from activation of dopamine-releasing neurons, when a placebo electronic cigarette is used it activates those sensory pathways and provides relief from cravings. Simply replacing nicotine intake will not subdue cravings completely; to do so other parallel pathways involved in the addiction must be stimulated. Because of this, electronic cigarettes are rising in popularity and making it easier for people to quit smoking while still maintaining the “cool” image factor of being a smoker.
Cellular mechanisms of nicotine addiction – Pharmacology Biochemistry and Behavior
A fresh look at tobacco harm reduction: the case for the electronic cigarette – Harm Reduction Journal