The use and abuse of drugs is a serious social and health problem on a global scale. Substance abuse kills, directly or indirectly, about 11.8 million people annually. Alcohol and nicotine take the dubious prize when it comes to fatality : 11.4 million people die earlier than expected each year. According to the WHO, up to half of the people who use tobacco end up dying thanks to it. The prevalence of substance use disorders is estimated at 1.5% of the world’s population, although in some disadvantaged regions this percentage rises to 5%. As low as these data may seem, do not be fooled: one in 5 people in the world (20%) uses tobacco. The fact that addictive behavior is not reflected in epidemiological data depends solely on whether the person is lucky in not paying for this dependence at a physiological level.
With all the statistics, we just want to make it clear that the use of addictive substances takes as many lives and causes as many pathologies as many pandemic events caused by viruses and bacteria. With the intention of taking a more biological and anatomical approach to this global problem, here we will review the issue of how drugs affect the nervous system .
The bases of drugs
The World Health Organization (WHO) defines a “drug” as any therapeutic substance or not that, introduced into the body by any route of administration, produces an alteration, in some way, of the natural functioning of the individual’s central nervous system and it is also capable of creating dependency. It should be noted that the dependence developed can be physiological, psychological or both.
The American Psychological Association (APA) recognizes several types of drugs for use, included in 10 different categories : alcohol, caffeine, cannabis, hallucinogens, inhalants, opioids, sedatives, hypnotics (including anxiolytics), stimulants (cocaine and others) and tobacco. These are the substances that are considered addictive today, but surely not the only ones.
Drugs and their effect on the nervous system of the human body
Let’s start with the basics: nicotine. When a person smokes a cigarette, the nicotine passes into the bloodstream, then to the brain and in just 7 seconds it causes the excitation of part of the neurons located in the ventral tegmental area (VTA) , which send the signals to the nucleus accumbens The latter is responsible for producing dopamine, the neurotransmitter and hormone that make us feel that “rush” or shock of well-being.
In the case of tobacco, this sensation is very ephemeral, because as soon as nicotine acts it stops doing so: the physiological peak of this drug is 7 seconds and its range of descent is another 7. Furthermore, the more they are exposed to neurons and circuits of the nucleus accumbens to the substance, the more of it will be necessary to elicit the desired response. This creates tolerance and long-term dependency.
To find out how drugs affect the nervous system, we can turn to another much more aggressive: heroin. This drug quickly enters the brain, attaches itself to opioid receptors in cells located in different areas and causes changes in the excitability of neurons, stimulating the presynaptic release of gamma-aminobutyric acid (GABA), among other things. When it comes into contact with this drug at the nervous level, it produces a generalized sedative effect and an indescribable well-being (the level of dopamine in the described reward system is increased by 200% in experimental models). All this causes euphoria, drowsiness, a sensation of heat and a gradual loss of consciousness, accompanied by a powerful analgesic effect. People who have used it are not lying when they claim to be “in a cloud” in the moments after the injection.
Finally, we can dissect the nervous effects of cocaine , the third of the drugs most present in the general culture. Once consumed, the effects at the level of the central nervous system are noticeable in a matter of 10 seconds (inhaled) and 3-5 minutes, if it is consumed intranasally. This compound inhibits the action of monoamine transporters, resulting in vasoconstriction in the blood system, elevated blood pressure, tachycardia, and increased cardiac output. All this reports a very characteristic feeling of activation and euphoria. Also Read: The Addictive Personality
Chronic cocaine abuse puts the patient at risk of many events, such as having a stroke (cerebrovascular accident), subarachnoid hemorrhages, intraparenchymal hemorrhages, and many other things. In general, every drug addict is seven times more likely to suffer an ischemic heart attack, a value that is multiplied even more in those who use cocaine.
Beyond all these mechanisms, it should be noted that dependence alone also modifies the functioning of the patient’s nervous system. When withdrawal syndrome occurs (72 hours after completely cutting off a substance), the person experiences anxiety, restlessness, difficulty concentrating, nervousness, stress, and other associated sensations. The addict’s brain can only function “normally” in the presence of the chemicals described. When they are removed, the nervous system fails.