Habituation to drugs: what it is, types, causes and characteristics.
Let's see what are the psychological and psychological mechanisms of habituation to drugs.
Habituation to drugs, better known in psychology under the name of toleranceis defined as the state of adaptation of the organism to the drug.
When we start consuming any type of drug, we observe that small amounts of it produce great effects, changes and sensations in the person. Large quantities are not necessary for our behavior to be altered by the narcotic. But if we continue consuming the same drug or similar drugs, we will notice that it does not produce the same effect as it did in the beginning, generally, this will be less, indicating that our body has become accustomed to the drug.
In the following article we will define the term tolerance, as well as we will see that this is divided into different typesWe will also learn what changes are produced in our organism when it habituates and we will see that the environment also influences the process of tolerance to the drug.
Keep reading if you want to know what changes the repeated consumption of a narcotic generates in your body, why the effect of this one is reduced or how to diminish the habituation.
What is habituation to drugs?
The habituation to the drugs, or also called tolerance, is defined as the state of adaptation of the organism that diminishes the response to the same amount of drug that previously produced a greater effect or the necessity of an increase of the dose of consumption to obtain the same effects that previously produced a greater effect. of consumption to obtain the same effects that were obtained at 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 habituation.
Characteristics of habituation
Habituation, as a general concept in psychology, is explained as the decrease of the individual's response to a stimulus the individual's response to a stimulus presented repeatedly.. It is a central process, that is, it is produced by a change in the central nervous system (CNS) and not by a state of fatigue of the individual or by a sensory adaptation. The response is innate, as opposed to extinction, where learning has taken place.
Some of its properties are stimulus specificity, which 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 is produced in different situations.
This process can present spontaneous recovery, which means that, with the passage of time, the response to the stimulus that had diminished 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 move on to see what kind of tolerances to drugs exist.
Types of drug habituation
In this section we will define the two types of drug habituation that exist, looking at how the body acts on the drug and how the substance generates changes in the organism, more specifically in its receptors.
1. Pharmacokinetic or metabolic tolerance
This type of habituation to the drug appears after repeated administration of the substance.This process accelerates the degradation mechanisms of the drug.
In this particular case, the change occurs especially in the substance, which shows a more rapid decrease in concentration in the organism, caused by the acceleration of its degradation.
2. Pharmacodynamic, pharmacological, neural or functional tolerance
This variant of habituation occurs when, after repeated consumption of the substance, the receptors of the drug become habituated, the receptors of the drug become habituated to the presence of the drug, generating a state of adaptation of the organism to the substance and, consequently, higher doses than those originally required are needed.
Unlike the other type of habituation, in pharmacodynamic tolerance there is a greater change in the organism, since in the places of reception of the drugs in the brain, there is an increase or decrease in the number and sensitivity to the substance.
Having mentioned the two types of tolerance, we will go on to describe two other terms related to habituation to drugs.
We will refer to this process when the consumption of a particular substance generates not only habituation to it, but also tolerance to other similar drugs. tolerance to other similar drugs is also present..
This would be the case, for example, of people with tolerance to alcohol, who will also show tolerance to tranquilizers, needing higher doses of these to notice the effect.
Inverse habituation occurs when, after the consumption of similar or even lower doses of the same drug, similar or greater effects are obtained, thus presenting the opposite result to the one obtained with the same drug.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 number of receptors.
Given the effects related to inverse tolerance, this is linked to the occurrence of over- or under-tolerance. is linked to the occurrence of overdose, without the need for the dose taken to be greater than that normally consumed..
Biological effects that habituation produces in the organism.
Known the different classes of tolerance, we go on to describe the effect, change, that is produced in the organism in each one of the different types of habitation.
Pharmacodynamic or functional tolerance
Due to the repeated consumption of the substance, the concentration of neurotransmitters (NT) in the synaptic space increases, this increasing number of NT consequently generates a decrease in the number of neuronal receptors, so as not to be constantly sending signals to the cells.
This decrease in the number of receptors is called down-regulation.. In the same way, it is also possible that the receptors become less sensitive, presenting a higher activation threshold.
Conversely, if there is a decrease in neurotransmitters if there is a decrease of neurotransmitters in the synaptic space, the receptors will increase in number or become more sensitive in order to take advantage of all those available. to take advantage of all those available. This process is called receptor up-regulation.
An example would be the decrease in the number and sensitivity of GABA A receptors after persistent alcohol consumption.
Pharmacokinetic or metabolic tolerance.
As we have already noted above, this tolerance is related to the more rapid decrease in the amount of substance by the organism. That is to say, after repeated use, 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 hepatic enzymes, such as the enzymes of the cytochrome P-450 system.
Influence of the context on drug habituation
The influence exerted by the context on drug habituation, produces what in psychology is known as conditioned tolerance.This concept, proposed by Siegel, is defined as the relationship produced between the contextual signals where the substance is consumed and the response given by the organism to this consumption.
This would imply that, in the usual context where the drug is consumed, the effects of the drug are reduced, attenuated, by the compensatory conditioned response produced by the environment, this response generally appears in the opposite direction to the effect produced by the substance.
An attempt has also been made to explain tolerance on the basis of Solomon and Corbit's (1974) opposing process theory (1974) or acquired motivation theory.
This theory states that, when an intense affective change, whether very positive or very negative, is produced, 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 initial phases of drug consumption, the substance produces pleasure; in these first moments "process b" is already activated, related to the sensation of displeasure, but to a lesser extent than "process a". This will make that in the computation of "process a" and "process b" the "process a" will be greater, generating, as it has already been pointed out before, a sensation of pleasure.
However, with repeated consumption, "process a", which produces pleasure, weakens. This fact is explained by the habituation that appears to the drug, tolerance. On the other hand, "process b" will continue to increase, becoming more intense and increasing the sensation of displeasure.
This event is related to the onset of abstinence.. In other words, finally the strongest and prevailing effect is the "b-process", thus causing the aversive motivation that will lead to the desire to avoid the withdrawal syndrome.
Control of established tolerance.
As we have presented in the previous section, tolerance may be due to a state of environmental conditioning. Therefore, it could be eliminated, or diminished, by using extinction, non-contingent reinforcement or external inhibition..
With regard to extinction, a process that appears due to the non-presence of a response to a previously reinforced stimulus, it has been shown that it occurs with different types of substances, such as morphine, and with different routes of administration, such as, for example, intravenous administration.
On the other hand, the non-contingent reinforcement process, consisting in the presentation, not paired, of conditioned stimulus (CS) and unconditioned stimulus (CS).. That is, the occurrence of the CS will signal the non-presentation of the CS. It has obtained positive results in the reduction of tolerance to the sedative effects of morphine in rats.
Finally, in reference to external inhibition, different authors have pointed out that the reduction of habituation to the drug should 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 onset of tolerance. The external inhibition effect would also reinforce the belief of environmental room specificity.
As an example of what has been presented in this section, we quote Linnoila (1986) who noted 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 are in circumstances not normally associated with ethanol, such as in a car".
(Updated at Mar 28 / 2023)