The effects of tobacco on the brain

Lighting and smoking a cigarette are actions that millions of people carry out regularly every day, even knowing that smoking and tobacco use have a large number of harmful and detrimental effects on our survival.

Today most know the relationship between tobacco 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 taken into account by the population and that despite this are fundamental: for example, the effects of tobacco on the brain.

Throughout this article we are going to do a brief review of what smoking involves, how tobacco affects the brain and the effects and risks that tobacco use can have on the king organ.

• Related article: "Parts of the human brain (and functions)"

Tobacco and nicotine

Tobacco is a product made from the tobacco plant (Nicotiana tabacum), specifically its leaves and stem, which after being minced or cut are prepared in different formats and some of which are mixed with other substances to form cigarettes, rolling tobacco or to use in pipes, and which is generally consumed by inhaling the smoke of its combustion.

The main active ingredient in tobacco, which gives it its psychoactive properties, is nicotine. This substance has activating and stimulating effects on the body, attaching itself to the nicotinic acetylcholine receptors of our body. Despite this, with chronic consumption and the progressive habituation that this substance generates, the effects are less and less activating and tend to be perceived as depressants and even relaxants.

But habituation to nicotine ends up generating dependence on its acquisition externally, in such a way that little by little little are needed larger amounts to obtain the same effects: over time smoking becomes a need and smoking or dependence on nicotine or tobacco is established.

The consumption of tobacco and the inhalation of its smoke also implies that other components, such as carbon monoxide, carcinogens, free radicals and oxidants such as hydroxyl radical, carcinogenic gases such as formaldehyde or nitric oxide or metals such as cadmium or beryllium (and even arsenic).

In addition, this consumption has harmful effects on multiple parts of our body, regardless of whether we are talking about tobacco in the form of cigarettes or in other modalities: smoke inhalation is irritating and is deeply linked to respiratory problems (one of the most common reasons being of chronic obstructive pulmonary disease, emphysema and other respiratory problems) and the development of respiratory or intestinal tract tumors and oropharyngeal.

It also affects, among others, the heart and the vascular system, generating vasoconstriction and can facilitate severe problems in said system. It can cause liver and pancreas problems, damage eyes and skin, and alter metabolism and the gastrointestinal system. It also reduces physical capacity due to lack of oxygenation.

How does smoking work in our brain?

Upon inhalation, most of this substance is absorbed by the smoker through the lungs (and in much less quantity by the mucous membranes and the tongue), and after having been processed by the alveoli and taken to the blood in about eight seconds reaches our brain after having passed through the barrier blood brain.

Once there, it fixes on the acetylcholine receptors called nicotinics, in which it generates the opening of calcium channels but preventing acetylcholine already existing in the brain from entering. This will cause the body to try to generate higher levels of acetylcholine, which will also cause the activation of the dopaminergic of the brain's reward system. Nicotine affects different parts 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.

This system is the cause that the consumption of tobacco gradually becomes palatable and encourages addiction. Dopamine in this area increases at the same time that other components of tobacco block the action of MAO that would decrease it. It also affects the locus coeruleus, stimulating it and causing an increase in energy levels at the same time that it contributes to generating feelings of tranquility in stressful situations.

Likewise, little by little, a desensitization of nicotinic receptors is generated through positive regulation. substance, to which the body will respond by forming a greater number of receptors where the union between nicotine and receiver. A tolerance to the substance is building, something that will cause more and more nicotine to be needed to cause the same effects. And this tolerance also partly explains why chronic smokers feel more relaxed when they smoke than being activated: they are actually relieving the anxiety of withdrawal.

At the same time, it affects the hypothalamic-pituitary axis in a way that increases the release of adrenocorticotropin and corticotropin-releasing hormones, which in turn contributes to the stimulation of the adrenal glands in such a way that it causes the synthesis and emission of adrenaline or epinephrine. This hormone will generate vasoconstriction and increases in pressure and heart rate and, in turn, feeds back the activation of the organism. It also hinders the synthesis of pancreatic enzymes.

Effects of tobacco on the brain

Beyond how it works, it is also relevant to know some of its effects. In the short term and with the first consumptions, it is usual that the initial consumption of small doses can alleviate depressive symptoms and increase mood.

Activation of the locus coeruleus also facilitates activation and there may appear to be increases in levels of wakefulness, ability to concentrate, and sense of coping. However, it can also cause palpitations, dizziness and respiratory problems.

However, as consumption becomes more frequent, worse and worse consequences are seen. In the first place, the progressive tolerance to nicotine has as a result that a dependence on the substance ends up appearing, initially physical and later also psychic.

Lack of tobacco will lead to withdrawal, usually in the form of discomfort and anxiety. Increased appetite, listlessness, headaches, and sleep problems are also seen. In abstinence, concentration problems can also appear. It also alters the capacity for olfactory and taste perception, damaging these senses.

The effect of nicotine on the neocortex has been observed, especially in the long term, as problematic and negative. Several studies suggest that tobacco use weakens and deteriorates the nerve cells of this part of the brain, and that causes a reduction in its thickness due to the higher mortality of the nerve fibers. This factor can be linked to an increased likelihood of cognitive decline 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 cause prematurity and low weight, as well as delays in growth and cognitive development of the child.

They also greatly affect the vasoconstrictive abilities of nicotine, something that can facilitate the occurrence of stroke. However, nicotine (not smoking) seems to have positive effects in preventing Parkinson's, although it is something that is still under study.

If we also take into account the possible effect of the presence of carbon monoxide (common in tobacco combustion), we also hinders oxygenation of the brain and they can cause demyelination of the nervous system (loss of myelin, which translates into a 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. At a less biological and more psychological level, unsuccessful efforts to quit may result Also feeling of helplessness or ineffectiveness, or even other substances may be resorted to. harmful.

Bibliographic references:

• 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 April 16; 54 (260): 31-41.