Health Effects of Smoking

TOLERANCE
Studies have demonstrated the rapid development of tolerance to the
effects of nicotine. When people begin to smoke, they experience a range
of rather unpleasant effects, such as dizziness or nausea, but these disappear
over days or weeks as the smoker continues to smoke. Tolerance to
other effects of nicotine develops even more rapidly. For example, when a
group of smokers was given two equal doses of nicotine sixty minutes
apart, they experienced more pronounced elevations of their heart rates
and reported greater subjective effects from the first dose compared to
the second.

 
WITHDRAWAL
On reporting for his first morning of smoking-cessation treatment after a
required day of abstinence, one of my patients summed up his feelings by
saying, “I want to hurt something.” As I scanned the room for sharp
objects, I realized that he was in nicotine withdrawal. Although not all
smokers are so extreme (or honest) in their feelings soon after quitting,
most report powerful cravings and irritability during the first two to three
weeks after their last cigarette. These are clearly symptoms of withdrawal.
As with tolerance, withdrawal from nicotine has both short- and longterm
aspects. For example, most smokers report that their first cigarette
of the day is the one that makes them feel best. This effect can be seen as
the termination of a mini-withdrawal after the overnight abstinence.

 
SUBJECTIVE EFFECTS

 

 
Although nicotine, particularly as administered by smoking, is clearly
addictive, it also clearly differs from many other addictive substances. It
lacks the obvious mind-altering effects of alcohol, stimulants, or opiates.
People don’t use nicotine because it provides a rush or a high. Rather,
most users report that it calms them and reduces anxiety. But even these
effects are more complicated than they may seem.  Because the vast majority
of nicotine users obtain it by smoking, we should consider smoking as a particular
kind of drug delivery. Many people derive considerable comfort and calming from
small personal habits or rituals—such as tapping a foot or humming to themselves—
and many such habits become associated with nicotine delivery during smoking.
Lighting up, holding the cigarette, moving it to and from the mouth and puffing—any
or all of these small rituals could calm the smoker in and of themselves and become
associated with the pharmacological effects of nicotine. Another consideration is that
the people who report the anti-anxiety and calming effects of smoking are most often
people who have been smoking for a while.  Thus, it is hard to know whether the
calming is a primary effect of nicotine or simply the reduction of an addicted person’s
craving.
Another commonly reported effect of smoking is the suppression of
appetite. Again, it is not clear if this effect is principally due to the nicotine
or the smoking, but animal studies show that nicotine can reduce eating when it is
given in the absence of smoke. In humans, smoking one cigarette has been shown
to diminish hunger contractions in the stomach. It is also possible that the appetite is
suppressed in part because smoking reduces the function of the taste buds in the
mouth. Other possibilities include the effects of smoking on energy metabolism and
bloodsugar levels. The fact is that we do not know exactly why smoking suppresses
appetite, but it seems clear that for some people it does. Of course, there is another
side to this coin: when a smoker quits smoking, his appetite often increases and he
gains weight. is could be due to the effects of the physical withdrawal of nicotine from
the system or to the need to replace the oral habits associated with the act of smoking.
EFFECTS ON THE BRAIN AND MENTAL FUNCTION
Before the 1980s, it was not at all clear how nicotine affected the brain. We
now know that nicotine stimulates a specific subtype of receptor for the
neurotransmitter acetylcholine—the nicotinic acetylcholine receptor.  These
receptors are distributed rather widely on nerve cells throughout the brain, so
nicotine has effects on a wide variety of brain structures. In general, it excites
nerve cells and increases cell-to-cell signaling. Several studies have shown that
nicotine increases the activity in brain regions that are associated with memory
and other mental functions, as well as in some structures involved with physical
movement.
When acetylcholine receptors in the brain are blocked, animals (and
people) have a difficult time remembering new information. Conversely,
some reports show that stimulating these receptors improves memory
somewhat. Because nicotine promotes the release of acetylcholine and
also activates its own subtype of acetylcholine receptors, some investigators
predicted that nicotine might enhance memory function. This appears to be
generally true in studies with animals, and a number of studies have been
undertaken to determine whether nicotine can help patients with memory
deficits, like those with early Alzheimer’s disease.

 

In such studies researchers generally administer nicotine either by injecting
it or by using a patch that allows it to be absorbed slowly through the skin.
Although it’s still uncertain whether nicotine may be of use to Alzheimer’s
patients, some convincing studies show that nicotine does improve some
mental functions for at least a brief time after its use. In a study that used the
nicotine patch, patients with mild to moderate Alzheimer’s disease showed
increased attention while exposed to nicotine. This does not mean, however,
that a person should smoke cigarettes or chew nicotine gum while studying
or during an exam or other activity that demands concentration or memory.
The carbon monoxide in the cigarette, combined with the lack of oxygen
exchange in the lungs due to the smoke, would likely lead to other side effects,
such as dizziness, which could easily overpower any potential attention- or
memory-enhancing effects of the nicotine. In addition, chewing nicotine gum
often delivers enough nicotine to make even experienced smokers feel
nauseated the first time or two.
Another potential medical use for nicotine is in the treatment of adult
attention deficit/hyperactivity disorder (ADHD). Although work on this
problem is not extensive, one study indicates that nicotine patch treatments
reduce ADHD symptoms in both smokers and nonsmokers. When
nicotine patches were used for four weeks, the capacity for attention in
both children and adults with ADHD was improved.

 

Nicotine may also prove helpful in people with schizophrenia—not as a
treatment for the psychotic symptoms but rather as an aid for cognitive function.
Schizophrenics often suffer learning and other cognitive deficits that are likely
due to impaired nicotinic receptors in the hippocampus.  The thinking is that if
nicotine is given, it will make up, in part, for that deficit in the function of the
hippocampus and thus improve cognitive function in the patient. Although this
research is still in the early stage, there is some compelling evidence that nicotine
may indeed diminish some cognitive deficits in adult schizophrenics.
Although these studies appear promising and may lead to more effective
treatments for these disorders, it is critical to remember three things. First, the
studies we mentioned have not yet led to any approved medical uses for nicotine
beyond its approval for use in smoking cessation. Second, several of the studies
have involved injections of nicotine, which, of course, should never be undertaken
without medical supervision. Third, those results should never be interpreted as a
reason to smoke. The health costs of smoking far outweigh any potential health
benefits of nicotine.
SMOKING AND EMOTIONAL FUNCTION
Depression is a common problem among adolescents. As many as 15 to 20 percent
of adolescents may become depressed at some time during this period. Smoking has
generally been regarded as a consequence of depression in young people, but it may
be that smoking leads to depression in some. It turns out that adolescents who are
smokers are twice as likely as nonsmoking adolescents to sffuer an episode of major
depression and that teens with long-term depression are more likely to be smokers than
teens without depression. Recent studies also show that depression at the age of fourteen
predicted smoking progression as teens age from fourteen to eighteen. This suggests that
increased smoking during the teen years could represent a form of self-medication for
depression. Although these findings do not tell us why a teen smoker is more likely to
become depressed or vice versa, they may provide valuable warning signals. A young
person who has problems with depression may be at higher risk than normal for smoking,
and it may be wise for such people to take special care to avoid situations in which smoking
is prevalent.  Likewise, a teen who smokes may be more susceptible to depression and
should watch for early signs of it so that antidepressant treatment can be started, if necessary.

 

EFFECTS ON THE HEART

 
It is well known that smoking causes lung cancer and other chronic lung
diseases. What is less well known is that smoking also contributes to diseases
of the heart and vascular system, which actually kill more people in the United
States annually than any cancer. Nicotine affects the heart in several ways.
The heart is a big muscle, and like all muscles it needs a rich supply of oxygen
to do its work pumping blood throughout the rest of the body. When nicotine is
in the system, it results in the release of adrenaline, which increases heart rate
and blood pressure. The heart then needs more oxygen to increase its workload,
but its oxygen supply doesn’t increase, so it must do extra work with no extra help.
What’s worse, the carbon monoxide in smoke also decreases the ability of the
blood to carry oxygen, making the situation even more stressful for the heart.
Repeatedly stressing the heart in these ways leads to damage and compromises
its function. Cigarette smoke is also directly toxic to the inner lining of the blood
vessels. Something in the smoke makes them hard and inflexible, adding to the
cardiovascular problems. It is estimated that as many as 30 percent of the
deaths attributed to heart and vascular disease relate to smoking.

 

All of these negative effects on heart and circulatory functions may
have another, less dangerous but unwanted effect. Smokers develop
thinner skin. A 1997 study of identical twins in which one twin smoked
and one did not showed that the smokers had skin that was thinner than
that of their twin siblings. Investigators think that this may be why
some smokers tend to have more wrinkles and look older than they are.
One possible explanation for this effect on the skin is that smoking can
decrease the blood supply to the topmost layer of the skin and thus
damage it.

 

 
SECONDHAND, THIRDHAND, AND
SIDESTREAM SMOKE

 

 
There are two sources of smoke from cigarette smokers: the smoke they
exhale (secondhand) and the smoke rising off the lit cigarette, cigar, or
pipe itself (sidestream). It is worth knowing that sidestream smoke has a
higher concentration of carcinogens than either secondhand smoke or the
smoke that a smoker takes into his lungs through a cigarette filter.  Whatever
the source, smoke can cause disease. The Environmental Protection Agency,
after considerable study of this issue, determined that secondhand smoke is
indeed a carcinogen in and of itself and is responsible for a signicant number
of lung cancer deaths each year in the United States. Of course, the amount
of exposure to secondary smoke is a critical factor in the risk of developing
lung disease (as is the smoker’s own amount of exposure), and a few parties
in smoky rooms will probably not kill anyone. However, people who spend a
lot of time in smoky places, like bars, or who live with smokers are clearly
placing themselves at some risk for lung disease. The effects of secondhand
smoke on the development of heart disease are even more alarming. A ten-year
study published in 1997 showed that regular exposure to secondhand smoke
can double a person’s risk of heart disease. This study of more than thirty
thousand women suggests that as many as fifty thousand people may die each
year in the United States as a result of heart attacks related to secondhand-smoke
exposure.  In enclosed areas where smoking occurs, the residue of the nicotine on
surfaces can react with normal chemicals present in the air to create carcinogens
that are found in tobacco. This toxic feature is referred to as “thirdhand” smoke,
though obviously it is not smoke per se. The actual health risks of such residues are
not clear. But it is a matter of current study and some public health researchers are
concerned that toddlers and young children may be at greater risk of exposure
because they are more likely than adults to touch and explore surfaces and put their
hands in their mouths or eat without washing their hands first.

 

 
PRENATAL AND POSTNATAL EFFECTS

 
As with most psychoactive drugs, nicotine passes to the fetus in the blood of the
pregnant woman who smokes (or otherwise uses nicotine). Babies born to smoking
moms have been shown to have levels of cotinine in their urine that are nearly as
high as those of active smokers. As time passes after birth and their nicotine levels
fall, these babies show symptoms of nicotine deprivation. The pregnant smoker
also passes along cyanide and carbon monoxide to her baby, both of which are very
bad for the developing fetus. Remember that carbon monoxide reduces the ability of
blood to carry oxygen and thereby depletes body tissues of oxygen. Also, nicotine
constricts blood vessels bringing blood to the fetus, further limiting oxygen supply. In
the fetus, this oxygen depletion is thought to account for the fact that babies born to
smoking mothers are smaller, lighter, and have smaller head circumferences than
babies born to nonsmoking mothers. In addition, as with alcohol, smoking during
pregnancy likely has lasting (perhaps permanent) effects on the brain and mental
function of the child after birth. Some studies have linked maternal smoking with
difficulties in verbal and mathematical abilities and hyperactivity during childhood. 
There’s also a greater likelihood of nicotine addiction in adulthood for people whose
mothers smoked during their pregnancy. Interestingly, maternal smoking did not
change the likelihood of people trying cigarettes, but it did significantly increase the
chances of them becoming addicted if they did initiate cigarette use.  This finding may
suggest that while experimenting with smoking may be driven largely by social forces,
the liability to addiction may be tied more closely to specific biological characteristics.

 

Once a baby is born, an immense amount of brain development is still going on.
Exposure of babies and small children to secondary smoke should also be avoided.
For example, some studies have suggested that there is an increased risk of sudden
infant death syndrome (SIDS) in babies of smoking mothers and that this could be due
to smoke in the environment. It is also possible that this could be due to damage that
the baby suffered before birth due to the mother’s smoking or to the combination of
prenatal and postnatal exposure.  Studies also indicate that the children of fathers who
smoke are more likely to develop childhood cancers than the children of nonsmoking
dads. Based on the Oxford Survey of Childhood Cancers, the study of some three
thousand parents showed that fathers who smoked twenty or more cigarettes per day
had a 42 percent increased risk of having a child with cancer and that those who smoked
ten to twenty cigarettes per day increased the risk by 31 percent. The risk was increased
by 3 percent for fathers who smoked fewer than ten cigarettes per day. These results
suggest that smoking may damage sperm in ways that could lead to cancer-causing
alterations of the DNA. The message is very clear—babies are best raised in a smoke-free
environment.

 

 

*Excerpted from Buzzed: The Straight Facts about the Most Used and Abused Drugs from Alcohol to Ecstasy, Fully Revised and Updated Fourth Edition by Cynthia Kuhn, PhD, Scott Swartzwelder, PhD and Wilkie Wilson, PhD. Copyright 2014, 2008, 2003, 1998 by Cynthia Kuhn, Scott Swartzwelder and Wilkie Wilson.  With permission of the publisher, W.W. Norton & Company, Inc.  All rights reserved

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