How does an addiction affect the brain?

A summary of the effects that addictions have on the brain and its functioning.

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

However, those who have an addiction have traditionally suffered social ostracism and rejection, as their problem was understood to be the result of personal weakness or even plain and simple wickedness. This is why they have been singled out and blamed for their situation on countless occasions, while denying them any option for reintegration.

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

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

What is an addiction?

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

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

There are a number of symptoms that allow the precise detection of addiction: craving (an irresistible desire to consume where it used to be done), tolerance (the need to use an increasingly higher dose of a drug in order to experience the same effect as at the beginning), withdrawal syndrome (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 on daily life. on daily life.

All these phenomena can be explained in a simple way by resorting to changes in the brain systems involved. Let's take a closer look.

The effects of addiction on the brain

All the behavioral/attitudinal symptoms that are evident in people suffering from addiction have a clear correlate in their brain. And the fact is that drug abuse has the capacity to promote neural adaptations that underlie the cognitive and affective experience of the abuser, which should never be perceived or interpreted as a "harmful" or "harmful" attitude. and should never be perceived or interpreted as a "pitiful" or "harmful" attitude. Such a judgment is unfair and inaccurate, reductionist in every sense, and not at all in line with current knowledge on the subject.

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

1. Beginning: the hedonic principle

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

Everything that people can do that generates pleasure is inexcusably stimulated by it. When we eat what we like the most, 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. encourage us to repeat these behaviors and/or activities on successive occasions.. In these cases, a discrete increase in the regional production of the neurotransmitter dopamine would be observed, although within the healthy physiological threshold.

However, when we observe in detail the functioning of the brain while using a substance (any of them), we can see that in this neuronal complex (formed by the nucleus accumbens, the ventral tegmental area and its specific projections to the prefrontal cortex) there is a "massive" discharge of the above mentioned neurotransmitter (dopamine). This activation is analogous to that evidenced by natural reinforcers, but with a single exception: the amount secreted is between two and ten times higher than that motivated by them, as well as much more immediate and clearer in the experience.

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

2. Maintenance: learning

Hyperactivation 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 consuming a substance would become addicted to it from the very moment it enters the organism, which is not the case. This process takes time and depends on the learning network that the individual weaves with the stimuli and sensations associated with the objective situation of consumption. Thus, there is a psychological component that contributes to forging dependence, together with the neurological and chemical ones.

Dopamine, the neurotransmitter that coordinates the pleasure response, also has among its many attributions a role in memory and learning.. This happens especially in collaboration with glutamate, which contributes to trace the functional relationship between drug consumption and its consequences or its environmental cues. Thus, the person will not only feel pleasure after using the substance, but will proceed to elaborate a complete map of the environmental and experiential topography of the same moment (what happens and what he feels), which will help him to understand his experience and orient himself when he yearns for those sensations again (looking for how to acquire and administer the drug).

This neurological process forges a cause-effect relationship that constitutes the foundation of addictions, and which is basic in explaining the link between subjective sensations and their connection with the drug used, which will later articulate a motor behavior aimed at seeking and consuming it (addictive habit). As the person repeats the association, the intensity of the association will become progressively stronger (closer connections between the nucleus accumbens and the prefrontal cortex). These brain changes finally translate into the deformation of the original pleasure, which would become a pressing and extremely invasive need. to become a pressing and extremely invasive need for pleasure..

At this point, the person has usually lost motivation for what was once the very center of his or her life (from social relations to personal projects), and focuses his or her efforts solely on consumption. All this is contributed to by the fact that structures of the primitive brain coordinate with those of more recent appearance (neocortex), giving shape to a pernicious alliance that deteriorates a large part of what was in the past.

3. Abandonment: tolerance and craving

The brain changes associated with consumption on the reward system involve an artificial modification of its natural function, so that the organ tries to adapt to it by generating a compensation that reverses it (with the ultimate goal of recovering homeostasis). Thus, when addiction has finally set in, it takes an inevitable toll: each time the drug causes less and less effect, so that the person is forced to increase the dose in order to perceive sensations comparable to those of the beginning (tolerance). to perceive sensations comparable to the initial one (tolerance).

This attenuation effect can be explained as follows: the substance promotes an increase in "dopaminergic availability" in the cleft of the synapses of the reward system, saturating the receptors for it located in the region. In order to correct this functional aberration, there would be a "down-regulation" of these receptors, resulting in a reduction of their presence and of the psychotropic effect on the way of feeling and thinking. The substance would thus lose its impact on the inner life, and a battle would be waged between the individual (who 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 engage in a compulsive search for the substance that would displace everything else. a compulsive search for the substance that would displace everything else.. When the substance is no longer available, an intense physical/affective discomfort will break out, which is called withdrawal syndrome (and which is expressed in the opposite way to the effect that the drug elicits during intoxication). All this can be even more difficult when the person suffering from dependence does not make changes in the dynamics of his daily life, and continues to live with the same stimuli with which he did when he was in the active phase of consumption.

These difficulties result from the involvement of two very specific brain structures: the hippocampus and the amygdala. While the former enables the creation of new content in memory, the latter is responsible for processing the emotions that follow from our experiences. When fused together, they facilitate craving, that is, an irresistible desire for consumption during exposure to environmental cues related to it. This phenomenon would be the result of the addictive history, and could be explained in a simple way through classical conditioning (syringes in syringe users). (syringes in injected heroin users, or the simple presence of people who used to accompany them during the acute effect, e.g.).

Conclusions: a complex process

The process through which an addiction is shaped is usually slow and insidious. In the first months or years its use is based on the pleasurable sensations secondary to it (reward system), but that soon gives way to a reduction of its effects and an impossible battle to relive them (as a result of neuroadaptation) in which biology ends up imposing itself. Such a process leads to a loss of motivation for everything that used to be enjoyablewith 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 abandon the cycle. To do so, he/she must cope with the general deterioration of his/her life, as well as with the urges to consume when he/she is located close to discriminative stimuli (related to his/her personal experience of addiction). It is the latter phenomenon that triggers craving, one of the most common reasons for relapses or slips. Its effects are due to the action of the hippocampus and the amygdala.

In short, addiction should never be explained by alluding to willpower alone, because it is underlain by 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 return to living a full and happy life.

Bibliographical references:

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