The effects of tobacco on the brain
Lighting up and smoking a cigarette are actions that millions of people carry out on a regular basis every day, even though they know that smoking and tobacco consumption have a great deal of harmful effects on our survival.
Today most people know the relationship between smoking and lung cancer, respiratory problems, the aging of our tissues or the shortening of life expectancy. However, there are other organs and affectations that are not usually so taken into account by the population and that are nevertheless fundamental: for example, the effects of tobacco on the brain.
Throughout this article we are going to make a brief review of what smoking implies, how tobacco affects the brain and the effects and risks that smoking can have on the king organ.
Tobacco and nicotine
Tobacco is a product made from the tobacco plant (Nicotiana tabacum), specifically from its leaves and stem, which after being chopped or cut are prepared in different formats and some of which are mixed with other substances to form cigarettes, rolling tobacco or for use in a pipe, and which is generally consumed by inhaling the smoke from its combustion.
The main active principle of tobacco, which gives it its psychoactive properties, is nicotine. This substance has activating and stimulating effects on the organism , binding to the nicotinic acetylcholine receptors of our body. Despite this, with the chronic consumption and progressive habituation that this substance generates, the effects are less and less activating and tend to be perceived as depressing and even relaxing.
But the habituation to nicotine ends up generating dependence to its acquisition by external means, in such a way that little by little greater quantities are needed to obtain the same effects: with the passage of time smoking becomes a necessity and smoking or dependence to nicotine or tobacco is established .
Tobacco use and the inhalation of its smoke also means that other components are incorporated into the body, such as carbon monoxide, carcinogenic substances, free radicals and oxidants such as the hydroxyl radical, carcinogenic gases such as formaldehyde or nitric oxide or metals such as cadmium or beryllium (and even arsenic).
Moreover, this consumption has harmful effects on many parts of our body, regardless of whether we are talking about tobacco in the form of cigarettes or other forms: smoke inhalation is irritating and is deeply linked to respiratory problems (being one of the most common reasons for chronic obstructive pulmonary disease, emphysema and other respiratory problems) and the emergence of respiratory tumors or intestinal and oropharyngeal tract.
It also affects the heart and the vascular system among others, generating vasoconstriction and may facilitate severe problems in that system. It can generate liver and pancreas problems, cause eye and skin damage and alter the metabolism and gastrointestinal system. It also reduces physical capacity due to lack of oxygenation.
How does smoking act on our brain?
Upon inhalation, most of this substance is absorbed by the smoker through the lungs (and in much smaller quantities through the mucous membranes and the tongue), and after being processed through the alveoli and carried to the blood in about eight seconds it reaches our brain after having passed through the blood-brain barrier.
Once there, it is fixed in the acetylcholine receptors called nicotinics, in which it generates the opening of calcium channels but prevents the acetylcholine already existing in the brain from entering. This will cause the body to attempt to generate higher levels of acetylcholine, which will also cause the activation of the dopaminergic in the brain’s reward system. Nicotine generates affectation in different points of the brain, but some of the most relevant are the limbic system and the basal ganglia , as well as the mesocortical and mesolimbic pathways.
It is this system that makes tobacco use gradually more appealing and promotes addiction. Dopamine in that area increases while other tobacco components block the action of MAO that would decrease it. It also affects the locus coeruleus, stimulating it and causing an increase in energy levels while contributing to feelings of tranquillity in stressful situations.
Also, gradually a desensitization of the nicotine receptors to this substance is generated by positive regulation, to which the body will respond by forming a greater amount of receptors where the bond between nicotine and receptor can occur. A tolerance to the substance is being formed , which will cause more and more nicotine to be needed to produce the same effects. And this tolerance also partly explains why chronic smokers feel more relaxed when they smoke than when they are activated: they are actually relieving the anxiety of withdrawal.
At the same time, it affects the hypothalamus-pituitary axis in a way that increases the release of adrenocorticotropic hormones and ACTH, which in turn contributes to the stimulation of the adrenal glands in such a way that it causes the synthesis and release of adrenaline or epinephrine. This hormone will generate vasoconstriction and increases in heart pressure and frequency and in turn feeds back the activation of the body. It also hinders the synthesis of pancreatic enzymes.
Effects of tobacco on the brain
Beyond how it acts, it is also relevant to know some of its effects. In the short term and with first consumptions, it is common that the initial consumption of small doses can alleviate depressive symptoms and increase mood.
The activation of the locus coeruleus also facilitates activation and may appear to result in increases in levels of wakefulness, ability to concentrate and the feeling of being able to cope. However, it can also cause dizziness and breathing problems.
However, as consumption becomes more frequent, the consequences become worse and worse. Firstly, the progressive tolerance to nicotine results in the appearance of a dependence on the substance, initially physical and later also psychic.
The lack of tobacco will generate abstinence, usually in the form of discomfort and anxiety . Increased appetite, apathy, headaches and sleep problems are also observed. In abstinence, concentration problems may also appear. It also alters the capacity of olfactory and gustatory perception, damaging these senses.
The effect of nicotine on the neocortex has been observed, especially in the long term, as problematic and negative. Various studies suggest that smoking weakens and causes deterioration of the nerve cells in this part of the brain, and that it causes a reduction in their thickness due to increased mortality of the nerve fibres. This factor can be linked to a greater likelihood of cognitive impairment and even dementia. It has also been seen that the formation of new neurons is reduced .
In case of pregnancy, it has been observed that smoking can generate prematurity and low weight, as well as delays in growth and cognitive development of the child.
They also greatly affect the vasoconstrictive capabilities of nicotine, which can facilitate the occurrence of stroke . However, nicotine (not smoking) appears to have positive effects on Parkinson’s prevention, although this is still being studied.
If we also consider the possible effect of the presence of carbon monoxide (common in the combustion of tobacco), also hinders the oxygenation of the brain and can cause demyelination of the nervous system (loss of myelin, which results in loss of speed in the transmission of information between neurons)
Also, although in the initial moments it generated stimulation, in the long run it can generate problems such as depression. On a less biological and more psychological level, if unsuccessful efforts are made to stop it, there may also be a feeling of helplessness or ineffectiveness, or even resorting to other more harmful substances.
- Dani, J.A. (2001). Overview of nicotinic receptors and their roles in the central nervous system. Biol. Psychiatry 49, 166-174.
- Karama, S., Ducharme, S., Corley, J., Chouinard-Decorte, F., Starr, J.M., Wardlaw, J.M., Bastin, M.E. & Deary, I.J. (2015). Cigarette smoking and thinning of the brain’s cortex. Molecular Psychiatry, 20: 778-785.
- Martín, A., Rodríguez, I., Rubio, C. Revert, C & Hardisson, A. (2004). Toxic effects of tobacco. Rev. Toxicol.,21: 63-71.
- Tanja, A.J., Quintero, L.C.M. (2015). Neurobiochemical effects of nicotine on the human brain. Magazine 16 April; 54 (260): 31-41.