Por qué la gente empieza a fumar Tomado del Taller de Capacitación para ONGs sobre Ratificación del CONVENIO MARCO PARA CONTROL DE TABACO de la Fundación Interamericana del Corazón

Why do people start smoking?

Experimenting with smoking usually occurs in the early teenage years and is driven predominantly by psychosocial motives. For a beginner, smoking a cigarette is a symbolic act conveying messages such as, in the words of the tobacco company Philip Morris, “I am no longer my mother’s child,” and “I am tough.” Children who are attracted to this adolescent assertion of perceived adulthood or rebelliousness tend to come from backgrounds that favour smoking (for example, with high levels of smoking in parents, siblings, and peers; relatively deprived neighbourhoods; schools where smoking is common). They also tend not to be succeeding according to their own or society’s terms (for example, they have low self esteem, have impaired psychological wellbeing, are overweight, or are poor achievers at school). The desired image is sufficient for the novice smoker to tolerate the aversion of the first few cigarettes, after which pharmacological factors assume much greater importance. Again in the words of Philip Morris, “as the force from the psychosocial symbolism subsides, the pharmacological effect takes over to sustain the habit.”Within a year or so of starting to smoke, children inhale the same amount of nicotine per cigarette as adults, experience craving for cigarettes when they cannot smoke, make attempts to quit, and report experiencing the whole range of nicotine withdrawal symptoms.

Physical and psychological effects of nicotine

Absorption of cigarette smoke from the lung is rapid and complete, producing with each inhalation a high concentration arterial bolus of nicotine that reaches the brain within 10-16 seconds, faster than by intravenous injection. Nicotine has a distributional half life of 15-20 minutes and a terminal half life in blood of two hours. Smokers therefore experience a pattern
of repetitive and transient high blood nicotine concentrations from each cigarette, with regular hourly cigarettes needed to maintain raised concentrations, and overnight blood levels dropping to close to those of non-smokers.

Nicotine has pervasive effects on brain neurochemistry. It activates nicotinic acetylcholine receptors (nAchRs), which are widely distributed in the brain, and induces the release of dopamine in the nucleus accumbens. This effect is the same as that produced by other drugs of misuse (such as amphetamines and cocaine) and is thought to be a critical feature of brain addiction mechanisms. Nicotine is a psychomotor stimulant, and in new users it speeds simple reaction time and improves performance on tasks of sustained attention. However, tolerance to many of these effects soon develops, and chronic users probably do not continue to obtain absolute improvements in performance, cognitive processing, or mood. Smokers typically report that cigarettes calm them down when they are stressed and help them to concentrate and work more effectively, but little evidence exists that nicotine provides effective self medication for adverse mood states or for coping with stress.

A plausible explanation for why smokers perceive cigarettes to be calming may come from a consideration of the effects of nicotine withdrawal. Smokers start to experience impairment of mood and performance within hours of their last cigarette, and certainly overnight. These effects are completely alleviated by smoking a cigarette. Smokers go through this process thousands of times over the course of their smoking career, and this may lead them to identify cigarettes as effective self medication, even if the effect is the negative one of withdrawal relief rather than any absolute improvement.

Regulation of nicotine intake

Smokers show a strong tendency to regulate their nicotine intakes from cigarettes within quite narrow limits. They avoid intakes that are either too low (provoking withdrawal) or too high (leading to unpleasant effects of nicotine overdose). Within individuals, nicotine preferences emerge early in the smoking career and seem to be stable over time. The phenomenon of nicotine titration is responsible for the failure of intakes to decline after switching to cigarettes with low tar and nicotine yields. Compensatory puffing and inhalation, operating at a subconscious level, ensure that nicotine intakes are maintained. As nicotine and tar delivery in smoke are closely coupled, compensatory smoking likewise maintains tar intake and defeats any potential health gain from lower tar cigarettes. Similar compensatory behaviour occurs after cutting down on the number of cigarettes smoked each day; hence this popular strategy fails to deliver any meaningful health benefits.

Socioeconomic status and nicotine addiction

An emerging phenomenon of the utmost significance over the past two decades has been the increasing association of continued smoking with markers of social disadvantage. Among affluent men and women in the United Kingdom, the proportion of ever smokers who have quit has more than doubled since the early 1970s, from about 25% to nearly 60%, whereas in the poorest groups the proportion has remained at around 10%. Part of the explanation for this phenomenon may be found in the growing evidence that poorer smokers tend to have higher levels of nicotine intake and are substantially more dependent on nicotine. It is evident that future progress in reducing smoking is increasingly going to have to tackle the problems posed by poverty.

Smoking as a chronic disease

Cigarette dependence is a chronic relapsing condition that for many users entails a struggle to achieve long term abstinence that extends over years or decades. Successful interventions need to tackle the interacting constellation of factors—personal, family, socioeconomic, and pharmacological—that sustain use and can act as major barriers to cessation.

Referencias

Encuesta Mundial del Tabaquismo en Jóvenes (EMTJ)
(28/Jul/2003) en español (407.86k)

La Asamblea Mundial de la Salud contemplará la adopción de un tratado mundial para el control del tabaco (15/May/2003) en español  (3.54k)  

Prevalence of and risk factors for cigarette smoking among adolescents in South America: a systematic literature review (15/May/2003) in english (4.12k)