How does an addiction affect the brain?

Addictions are phenomena whose root has a neurological basis. Studies on this issue agree that the brain is the axis around which the brain orbits. clinical expression of the same, so it is concluded that behind there always lies some nuance organic.

However, those with an addiction have traditionally suffered social ostracism and rejection, when it was understood that his problem was the result of a personal weakness or even the simple and plain evil. That is why they have been singled out and blamed for their situation countless times, while denying them any option for reintegration.

Today it is known that consumption begins as an unfortunate decision, motivated and sustained by personal or social circumstances; but that diverse forces participate in its "maintenance" that it is not easy to deal with (anatomical / functional changes in neurology itself).

In this article we will explore how drug use affects the brain and behavior, so that both its causes and consequences can be detailed in depth. It is from this that we can better understand the "how and why" of a health problem of enormous human and social importance. The purpose is to answer this question:

How does addiction affect the brain?

• Related article: "The 14 most important types of addictions"

What is an addiction?

The word "addiction" comes from the classical languages, and more specifically from the Latin term "addictio", which is literally translated as "slavery". From the very origin, therefore, it follows that those who fall into its clutches are deprived of the freedom to think and act freely.

Drug dependence is a chronic disorder due to structural and functional modifications on brain tissues, whose etiology has two possible sources of identical contribution: genetics and learning (the biology can explain 40% -60% of the variance based on comparative studies conducted with twins monozygotic).

There are a series of symptoms that allow the precise detection of addiction: craving (an irresistible desire to consume where it used to be), tolerance (the need to use an increasingly high dose of a drug in order to experience the same effect as at the beginning), the syndrome of withdrawal (severe discomfort when the administration of the substance is stopped), loss of control (excess time spent consuming and recovering from its effects) and difficulty in stopping the habit despite its negative impact about everyday life.

All these phenomena can be explained in a simple way by resorting to changes in the brain systems involved. Let's see it in detail.

The effects of addiction on the brain

All the behavioral / attitudinal symptoms that are evident in people who suffer an addiction have a clear correlate in their brain. And is that drug abuse has the ability to promote neural adaptations that underlie cognitive and affective experience of those who present it, and that they should never be perceived or interpreted as a "plaintive" or "harmful" attitude. Such a judgment is unfair and imprecise, reductionist in every way, and not at all adjusted to current knowledge on the matter.

Let's look at the addictive process from its very beginning, and as in all its phases, a neurological mechanism can be found that gives a good account of it.

1. Start: the hedonic principle

Pleasure is one of the essential engines of human behavior. It is the spring that triggers the desire to approach a stimulus in the environment, or to repeat a particular adaptive behavior for life. Among them are sex, eating or playful activity; for which a common brain mechanism is known that promotes their search and their achievement. Specifically, in the deepest abysses of this organ can be found a neural network that is "activated" when we experience a pleasant event (or we perceive subjectively as positive): the reward system.

Everything that people can do and that generates pleasure inexcusably passes through their stimulation. When we eat what we like the most, we have sex or simply share happy moments in the company of a loved one; This set of structures is responsible for us feeling positive emotions that encourage us to repeat these behaviors and / or activities on successive occasions. For these cases, a discrete rebound in regional production of the neurotransmitter would be observed. dopamine, albeit within the healthy physiological threshold.

However, when we observe in detail the functioning of the brain while using a substance (any of them), it is appreciated that in this neuronal complex (formed by the nucleus accumbens, the ventral tegmental area and its specific projections towards the prefrontal cortex) there is a "massive" discharge of the aforementioned neurotransmitter (the dopamine). This activation is analogous to that seen in natural enhancers, but with only one caveat: the amount segregated is between two and ten times higher than that caused by these, as well as much more immediate and clear in the experience.

The result of such a process is that the person feels intoxicated by a great sensation of pleasure right after consuming the drug. (although the time it takes to break in depends on its chemical properties and the route chosen for its administration), to such an extent that it exceeds that of any reinforcer available in the environment natural. The main problem that underlies all this is that, with the passage of time, what was gratifying would cease to be; substituting itself for the drugs on which it depends. The result is often the loss of very important relationships and the deterioration of work or academic responsibilities.

• You may be interested: "Parts of the human brain (and functions)"

2. Maintenance: learning

Overactivation of the reward system and the associated experience of pleasure is only a first step towards chemical addiction, but not the only one. Otherwise, any person who consumed a substance would become addicted to it from the precise moment they entered the body, which is not the case. This process requires time, and depends on the learning network that the individual comes to weave with the stimuli and with the sensations associated with the objective consumption situation. Thus, there is a psychological component that would contribute to forging dependence, along with neurological and chemical ones.

Dopamine, the neurotransmitter that coordinates the pleasure response, also has among its many attributes a role in memory and learning. This happens especially in collaboration with glutamate, which helps to trace the functional relationship between drug use and its consequences or environmental clues. Thus, the person will not only feel pleasure after using the substance, but will proceed to develop a complete map of the environmental and experiential topography of it. moment (what happens and what you feel), which will help you understand your experience and orient yourself when you yearn for those sensations again (find how to acquire and manage the drug).

This neurological process forges a cause-effect relationship that constitutes the foundation of addictions, and that is essential in explaining the link between addictions. subjective sensations and their connection with the drug used, which will later articulate a motor behavior directed at their search and consumption (habit addictive). As the person repeats the association, its intensity will progressively strengthen (closer connections between nucleus accumbens and prefrontal cortex). These brain changes are ultimately translated into the deformation of the original pleasure, which would become a pressing need and extremely invasive.

At this point, the person has often lost motivation because of what was once the very center of his life (from social relationships to personal projects), and focuses his efforts solely on consumption. To all this contributes the fact that structures of the primitive brain are coordinated with those of more recent apparition (neocortex), shaping a pernicious alliance that erodes much of what was left in the past.

3. Abandonment: tolerance and craving

The brain changes associated with consumption on the reward system suppose an artificial modification of its natural function, in such a way such that the organ tries to adapt to it, generating compensation that reverses it (with the ultimate goal of recovering homeostasis). So when addiction finally sets in, it takes an inevitable toll: each time the drug causes minor effects, so the person is forced to increase the dose to perceive sensations comparable to that of the beginning (tolerance).

Such attenuation effect can be explained as follows: the substance promotes an increase in "dopaminergic availability" in the cleft of the synapse of the reward system, saturating the receivers for it located in the region. In order to correct this functional aberration, there would be a "downward" regulation of them, whose result would be the reduction of its presence and of the psychotropic effect on the way of feeling and think. The substance would thus lose its impact on the inner life, and a battle would be fought between the individual (which would increase consumption) and his brain (which would compensate for all this "effort").

At this point in the process, the subject (who is already deeply affected by the neurological changes of the addictive process) would incur a compulsive search for the substance that would displace everything else. When this is not available, an intense physical / affective discomfort would break out that is called withdrawal syndrome (and that is expressed in a way opposite to the effect that the drug elicits during the poisoning). All this can be even more difficult when the person who suffers from a dependency does not make changes in the dynamics of his day to day, and continues to live with the same stimuli that he did when he was in an active phase of consumption.

These difficulties result from the participation of two very specific brain structures: the hippocampus and the amygdala. While the first one enables the creation of new memory content, the second one is in charge of processing the emotions that arise from our experiences. When they merge, they facilitate craving, that is, an irresistible desire for consumption during exposure to the environmental cues related to it. This phenomenon would be the outcome of the addictive story, and could be explained simply through classical conditioning (syringes in injected heroin users, or the simple presence of people who used to accompany her during the acute effect, for example).

Conclusions: a complex process

The process through which an addiction is shaped is often slow and insidious. In the first months or years, its use is based on the pleasant sensations secondary to it (reward system), but they do not take long to stop. step to a reduction in their effects and an impossible battle to live them again (as a result of neuroadaptation) in which biology ends imposing itself. Such a process leads to a loss of motivation for everything that used to be pleasant, with a progressive withdrawal from social life and / or from one's own responsibilities or hobbies.

When this happens (through the network of connections between the nucleus accumbens and the prefrontal cortex), the person may try to leave the cycle. To do this, he must face the general deterioration of his life, as well as the impulses to consume when he is located near discriminating stimuli (related to his personal experience of addiction). It is this last phenomenon that triggers craving, one of the reasons for which relapses or slips are most commonly manifested. Its effects are due to the action of the hippocampus and the amygdala.

Definitely, addiction should never be explained by referring only to the will, since it underlies neural dimensions that must be addressed. The stigma and rejection that many people face when trying to recover from this problem is a dam to the flow of their motivation to live a full and happy life again.

Bibliographic references:

• Marco, D. (2013). The Addicted Brain. Frontiers in psychiatry / Frontiers Research Foundation, 4, 40.
• Volkow, N., Wang, G., & Fowler, J. and Tomasi, D. (2011). Addiction Circuitry in the Human Brain. Annual review of pharmacology and toxicology, 52, 321-336.