Hey, Pass Me a Light Please

What Causes Smoking Addiction:  Nicotine or Dopamine?

Growing up, I have always been told that smoking is bad.  Smoking is hazardous.  Smoking costs money.  Smoking looks unappealing.  Smoking kills.  Yet, despite all of these warnings and lessons, that surely most people have heard before, millions of people still light up.  Why, why do people continue to participate in an activity that is commonly associated with health risks such as cancer?  The most frequently used answer is an addiction to nicotine.  And this notion that nicotine causes addiction was continuously lectured to me in past mandatory health classes.  Yet, at the same time nicotine was used as an explanation, it was an incomplete reason.  What role does the substance play to result in this need for a cigarette?  Nicotine stimulates dopamine, a chemical in the brain that affects learning, motivation and pleasure [1].  Scientists have further explored the role of dopamine on addiction and are now suggesting theories that dopamine is the cause of addiction.  So, perhaps it is not nicotine that causes the addiction, but the role dopamine plays that causes the need to smoke.

Although cigarettes are the size of a finger and look like they are composed of paper and chopped up leaves, the composition of the sticks is complex.  Cigarettes contain tobacco that is made of a blend of two leaf types.  {Additives and flavoring are put into the blend to sweeten the taste of cigarette smoke.}  Nicotine is found in the moisture that emits from the leaves when they burn.  This moisture is taken in by the smoker because it attaches itself to the tobacco smoke that gets inhaled.  It only takes a few seconds before nicotine reaches the brain. [2] Cigarettes contain 1.2-2.9 mg of nicotine, the amount varying by brand.  About 3 mg of nicotine is inhaled from a single cigarette.  For someone who smokes a pack in a single day, their nicotine retention is anywhere between 20-40 mgs. [3]

Depending on the dosage of nicotine, the effects vary as well.  Short doses cause alertness and reduce fatigue.  Long doses result in a sedation and euphoria.  In this way, nicotine acts as a stimulant and a depressant.  A person’s heart rate speeds up as their blood vessels constrict.  When the drug goes straight to the brain, it impacts the hypothalamic-pituitary axis and then affects the endocrine system.  Through the system, it pumps up the level of endorphins and several other chemicals that affect stress. [3]
In a sense, the brain is told by nicotine to give ‘rewards’ and place the smoker in a relaxed state.

Nicotine also affects dopamine levels.  When nicotine attaches it to nerve cells, the nerve cells affect glutamate.  In turn, glutamate, a chemical signal, is stimulated.  Neurons connected to the glutamate are told to release dopamine.  The more the dopamine, the better sense of a good feeling ensures. [4]

As a neurotransmitter, dopamine affects processes in the brain.  The transmitter is most commonly related to pleasure and desire but it is also involved in movement, memory and learning. [1]

Using illegal drugs such as heroin and cocaine result in a massive release of dopamine.  Because of this, it was believed that dopamine was just the pleasure switch.  It has recently been discovered that dopamine has more than one role.  Being the pleasure switch is one of its lesser roles; its main niche is to tell the brain and the body to acknowledge and remember certain chemicals that are important for survival.  This is the salience theory- the release of dopamine happens during an important event whether or not it is good or bad. [1] Dopamine highlights the occurrence, helps the brain and body in recognizing what happens to oneself in this occasion and how it affects survival.

With the induction of nicotine or any other drug, dopamine levels skyrocket anywhere from five to ten times as much as a regular release.  In drug users, the brain adjusts to this flood of dopamine by dulling the system through decreasing its number of dopamine receptors in the areas of the brain involved in motivation and pleasure.  At the same time, the areas of the brain that control behavior (judgment and inhibitory) are weakened because of the dampening of the dopamine system. [1] This decreased amount of dopamine receptors coupled with the desensitization of the brain’s control of behavior leads to more use of the drug- an addict.  Less pleasure is received, because of the depression of dopamine receptors, and to compensate for that lost, addicts need more of the drug.

What causes an addiction to cigarettes?  Perhaps the first aspect that needed to be tackled is what an addiction is.  According to Ann Marlowe, a former drug user and memoir writer, her continual use of heroin was chasing the memory of her first time with the drug.  This chase, in my opinion, was an addiction to her initial experience with heroin.  An addiction is the search of an experience that made a lasting impression.  From my belief then, it would make sense that dopamine, not nicotine, is the cause of smoking addiction since dopamine tells the brain to remember this feeling of nicotine in the body.  This lasting impression can be affected by anything, however.  The issue raised then is whether or not this ‘outside’ factor on an impression also has an effect on dopamine levels.

And perhaps the smoker has a mental addiction to smoking.  ‘Finding relief in the motions of smoking a cigarette’ was what one girl in my health class said.  However, I am skeptical as to whether it is just the motions that she is addicted to.  And what about those who have smoked a cigarette once and have never smoked another one again?  Was their reaction to smoking not strong enough for dopamine to register the act as something needed for survival?  Does knowledge of possible addiction affect chemicals like dopamine and tell the brain that smoking is not needed for absolute survival?

What causes an addiction to cigarettes- nicotine or dopamine?  The answer may be an addiction to nicotine, but dopamine causes the actual addiction to occur.  Nicotine is what affects the release of dopamine.  And dopamine is what results in the craving for nicotine.  But then, what about all the other factors, internal and external that may have a role in addiction or a role that affects nicotine or dopamine?  When looking for a clear cut answer, I discovered that there is none.  The problem in answering this question lies in the question itself.  There does not seem to be a black and white answer, a simple explanation for what seemed to be a simple question.

 [1] http://groups.msn.com/FreedomFromTobaccoQuitSmokingNow/addiction.msnw?action=get_message&mview=0&ID_Message=256152&LastModified=4675572759122348559
[2] http://www.ash.org.uk/html/factsheets/html/fact12.html
[3] http://www.emedicine.com/med/topic1642.htm
[4] http://chronicle.uchicago.edu/020328/nicotine.shtml