Habituation to drugs: what is it, types, causes and characteristics

Habituation to drugs, better known in psychology as tolerance, is defined as the state of adaptation of the organism to the drug.

When one begins to consume any type of drug, we observe that small amounts of this produce great effects, changes and sensations in the person. Large amounts are not necessary for our behavior to be altered by the narcotic. But if we continue to consume the same drug or similar drugs, we will notice that it does not produce the same effect as produced at first, generally, this will be less, indicating that our body has become accustomed to the drug.

In the following article we will define the tolerance term, as well as we will see that it is divided into different types; We will also know what changes are produced in our body when it habituates and we will see that the environment also influences the process of tolerance to the drug.

Read on if you want to know what changes the repeated use of a narcotic generates in your body, because its effect is reduced or how to reduce habituation.

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What is habituation to drugs?

Habituation to drugs, or also called tolerance, is defined as the adaptive state of the body that decreases the response to the same amount of drug that previously produced a greater effect or the need for an increase in the dose consumption to obtain the same effects that were obtained in the beginning. In other words, it is the decrease in the effect of the drug when consuming it repeatedly.

Before continuing with the specific case of habituation to drugs, let's see how Psychology describes the term of habituation.

Habituation characteristics

Habituation as a general concept in Psychology, is explained as the decrease in the individual's response to a repeatedly presented stimulus. It is a central process, that is, it is produced by change in the Central Nervous System (CNS) and not by a state of fatigue of the individual or by a sensory adaptation. The answer is innate, differentiating itself from extinction where learning did occur.

Some of its properties are stimulating specificity, this means that there will only be a decrease in the response to the specific stimulus that has produced habituation and generalization, habituation to the specific stimulus occurs in different situations.

This process can present spontaneous recovery, which means that, over time, the response to the stimulus that had decreased due to habituation increases again, returning to the initial state.

Having understood the process of habituation and more specifically that of habituation to drugs, we will go on to see what kind of drug tolerances exist.

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Types of habituation to drugs

In this section we will define the two types of habituation to drugs that exist, seeing how the body acts on the drug and how the substance generates changes in the body, more specifically in its receivers.

1. Pharmacokinetic or metabolic tolerance

This type of habituation to the drug appears after repeated administration of the substance, a process that accelerates the degradation mechanisms of this drug.

In this specific case, the change occurs especially in the substance, which presents a decrease in concentration in the body faster, caused by the acceleration of its degradation.

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2. Pharmacodynamic, pharmacological, neural, or functional tolerance

This variant of habituation occurs when, after repeated consumption of the substance, drug receptors become accustomed to its presence, generating a state of adaptation of the body to the substance and, consequently, higher doses are required than those initially required.

Unlike the other type of habituation, pharmacodynamic tolerance causes a greater change in the organism, since in the places of reception of drugs in the brain, there is an increase or decrease in the number and sensitivity to substance.

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Cross tolerance

After mentioning the two classes of tolerances, we will now describe two other terms related to drug habituation.

We will refer to this process when the consumption of a specific substance generates not only habituation to it, but also tolerance to other similar drugs will also occur.

This would be the case, for example, of people with tolerance to alcohol, who will also have tolerance to tranquilizers, needing higher doses of these to notice an effect.

Reverse tolerance

Reverse habituation appears when, after the consumption of similar or even lower doses of the same drug, similar or greater effects are obtained, thus presenting a result contrary to that expected by habituation, hence the name inverse tolerance.

This paradoxical process is possibly due to the accumulation of the drug in certain tissues of the body and its subsequent release, or to a hypersensitization of the substance receptors. That is, an increase in the function or the number of receptors.

Given the effects related to reverse tolerance, this is associated with the appearance of overdose, without the need for the dose taken to be greater than that normally consumed.

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Biological effects that habituation produces in the body

Known the different classes of tolerance, We proceed to describe the effect, change, that occurs in the body in each of the different types of room.

Pharmacodynamic or functional tolerance

Due to repeated consumption of the substance, the concentration of neurotransmitters (NT) in the synaptic space increases, this increasing number of NTs consequently generates a decrease in the number of neuronal receptors, so as not to be constantly sending signals to the cells.

This decrease in receptors is called downregulation.. In the same way, it is also possible that the receptors become less sensitive, presenting a higher activation threshold.

Contrary, if there is a decrease in neurotransmitters in the synaptic space, the receptors will increase in number or become more sensitive to take advantage of all that are available. This process has the name of upregulation of the receptors.

An example would be the decrease in the number and sensitivity of GABA A receptors after persistent alcohol consumption.

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Pharmacokinetic or metabolic tolerance

As we have already pointed out previously, this tolerance is related to the faster decrease in the amount of substance by the body. That is to say, after repeated consumption the metabolism becomes more and more efficient in degrading and eliminating the drug.

For example, in the case of alcohol, there would be an acceleration of metabolism induced by liver enzymes, as is the case of the enzymes of the cytochrome P-450 system.

Influence of the context on drug habituation

The influence that the context exerts on drug habituation, produces what is known in Psychology as conditioned tolerance, a concept proposed by Siegel, defined as the relationship produced between the contextual signals where the substance is consumed and the response given by the organist to this consumption.

This would mean that, in the usual context where the drug is consumed, its effects are reduced, attenuated, by the response conditioned compensatory effect produced by the environment, this response generally appears in the opposite sense to the effect produced by the substance.

An attempt is also made to explain tolerance starting from Solomon and Corbit's opponent process theory (1974) or theory of acquired motivation.

This theory states that, when there is an intense affective change, either very positive or very negative, it is usually accompanied by the opposing affect. The first intense affective change will be called "process a" and the opposing affect will be called "process b".

In the early stages of drug use, the substance produces pleasure; in these first moments, “process b” is already activated, related to a feeling of displeasure, but to a lesser extent than “process a”. This will make the computation of "process a" and "process b" greater than "process a", generating, as mentioned before, a sensation of pleasure.

However, with repeated consumption, the “process a”, which produces pleasure, weakens. This fact is explained by the habituation that appears to the drug, tolerance. On the other hand, the "process b" will continue to increase, becoming more intense, and increasing the feeling of unpleasure more and more.

This event is related to the onset of withdrawal. That is to say, finally the most powerful effect and the one that prevails is "process b", thus causing the aversive motivation that will lead to wanting to avoid the withdrawal syndrome.

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Control of established tolerance

As we have presented in the previous section, tolerance may be due to a state of environmental conditioning. Therefore, could be eliminated, or decreased, using extinction, non-contingent reinforcement, or external inhibition.

Regarding extinction, a process that appears due to the lack of response to a stimulus previously reinforced, it has been seen that it occurs before different types of substances, such as be the morphine, and before different routes of administration, such as, for example, intravenous.

On the other hand, the non-contingent reinforcement process, consisting of the presentation, non-pairing of conditioned stimulus (CS) and unconditioned stimulus (EI). In other words, the appearance of the CB will indicate the non-presentation of the CB. It has obtained positive results in reducing tolerance to the sedative effects of morphine in rats.

Finally, in reference to external inhibition, different authors have pointed out that the reduction in drug habituation would be due to the presentation of a novel stimulus in the context. This fact would produce an orientation response to the new stimulus, which interferes with the appearance of tolerance. The external inhibition effect would also reinforce the belief of environmental specificity of the room.

As an example of what is presented in this section, we will cite Linnoila (1986) who pointed out that: “It is possible that subjects who show tolerance to the effects of ethanol in a meeting or in a bar, lose that tolerance when they find themselves in circumstances not normally associated with ethanol, such as in a car. "