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 some organic nuance always lies behind it.

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

Today we know that consumption begins as an unfortunate decision, motivated and sustained by personal or social circumstances; but that in its “maintenance” diverse forces participate with which it is not easy to deal (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 is literally translated as “slavery”. From the very beginning, 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 in brain tissues , whose etiology has two possible sources of identical contribution: genetics and learning (biology can explain 40%-60% of the variance according to comparative studies with monozygotic twins).

There are a number of symptoms that allow for accurate detection of addiction: craving (an irresistible desire to consume where it used to be), tolerance (the need to use an increasingly higher dose of a drug in order to experience the same effect as in its early stages), withdrawal (strong discomfort when the substance is stopped), loss of control (excess in the time spent consuming and recovering from its effects) and the difficulty in stopping the habit despite its negative impact on daily life.

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

The effects of addiction on the brain

All behavioural/attitudinal symptoms that are evident in people who suffer from an addiction have a clear correlation in their brain. This is because drug abuse has the capacity to propitiate neural adaptations that underlie the cognitive and affective experience of those who present it, and which should never be perceived or interpreted as a “pitiful” or “harmful” attitude. Such a judgment is unjust and imprecise, reductionist in all senses, and not at all in keeping with current knowledge on the subject.

Let us 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. Beginning: the hedonic principle

Pleasure is one of the essential motors 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 to life. Among them are sex, eating or playful activity; for which a common brain mechanism is known that promotes its search and achievement. Specifically, in the deepest abysses of this organ we can find a neuronal network that is “activated” when we live a pleasant event (or we perceive it subjectively as positive): the reward system.

Everything that people can do that generates pleasure inexcusably passes through their stimulation. When we eat what we like best, have sexual relations 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 behaviours and/or activities on successive occasions . In these cases, a discreet 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 towards the prefrontal cortex) a “massive” discharge of the mentioned neurotransmitter (dopamine) is produced. This activation is analogous to that seen in natural enhancers, but with a single exception: the amount secreted is between two and ten times higher than that caused by them, 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 sense of pleasure just 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 booster available in the natural environment. The main problem behind all this is that, with the passage of time, what was rewarding would cease to be so; it would be replaced by the drugs on which one depends. The result is often the loss of very important relationships and the deterioration of work or academic responsibilities.

2. Maintenance: learning

The 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, anyone who uses a substance would become addicted to it from the very moment he or she accesses the body, which is not the case. This process requires time, and depends on the network of learning that the individual manages to weave with the stimuli and sensations associated with the objective situation of consumption. Thus, there is a psychological component that would contribute to forge the dependence, together with the 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 keys. 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 to orient himself when he longs again for those sensations (to look for how to acquire and administer the drug).

This neurological process forges a cause-and-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 directed towards its search and consumption (addictive habit). As the person repeats the association, the intensity of it will progressively strengthen (closer connections between nucleus accumbens and prefrontal cortex). These cerebral changes are finally translated into the deformation of the original pleasure, which would become a pressing and extremely invasive need .

At this point, the person has often lost motivation for what was once the very center of his life (from social relationships to personal projects), and focuses his efforts solely on consumption. Contributing to this is the fact that the 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 went before.

3. Abandonment: tolerance and craving

The brain changes associated with consumption on the reward system imply 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 the addiction has finally been established, it takes an inevitable toll: each time the drug provokes lesser effects, so the person is forced to increase the dose to perceive sensations comparable to that of the principle (tolerance).

This attenuation effect can be explained as follows: the substance promotes an increase in “dopamine availability” at the synapse cleft of the reward system, saturating the reward receptors located in the region. In order to correct this functional aberration, a “downward” regulation of the receptors would be given, which would result in the reduction of their presence and 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 ensue between the individual (which would increase consumption) and his or her brain (which would compensate for all that “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 substance is not available, an intense physical/emotional discomfort, called withdrawal syndrome (expressed in the opposite way to the effect that the drug elicits during intoxication), would break out. All this can be even more difficult when the person suffering from a dependency does not make any changes in the dynamics of his day-to-day life, and continues to live with the same stimuli as when he was in an 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 the memory, the latter is responsible for processing the emotions that follow on from our experiences. When they merge they facilitate craving, that is, an irresistible desire to consume during exposure to the environmental keys related to it. This phenomenon would be the result of the addictive history, and could be explained in a simple way through the classic conditioning (syringes in users of injected heroin, or the simple presence of people who used to accompany it during the acute effect, e.g.).

Conclusions: a complex process

The process by 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 soon gives way to a reduction of its effects and an impossible battle to live them again (as a result of neuroadaptation) in which biology ends up imposing itself. Such a process leads to a loss of motivation for everything that was previously 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 so, he must cope with the general deterioration of his life, as well as with the impulses to use when he is located near discriminating stimuli (related to his personal experience of addiction). It is the latter phenomenon that triggers craving, one of the most common reasons for relapse or slippage. Its effects are due to the action of the hippocampus and the amygdala.

In short, addiction should never be explained by alluding only to the will, since there are neural dimensions underlying it that must be addressed . The stigma and rejection that many people face when they try to recover from this problem is a dam to the flow of their motivation to return to living a full and happy life.

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.