5 Effects of Drugs on the Nervous System

It has been proven that drug use has an effect on the functioning and structure of the nervous system, these alterations being very durable and inducing behaviors that may endanger the life of the addict (Volker, 2014).

Drug abuse is an important public health problem, as the continued use of these drugs can lead to serious consequences.

Effects of Drugs on the Nervous System

These include increased tolerance to certain substances, sensitization to others, and the emergence of a state of dependence that keeps the individual in a strong desire to re-consume.

In addition, if you spend a certain period of time without consuming, you may experience annoying withdrawal symptoms, which are opposed to the sensations that a drug can simulate.

Addiction is described as a lifelong disease that is characterized by search behaviors of the addictive substance and its compulsive consumption regardless of whether it causes negative consequences.

Addiction is associated with an increased likelihood of relapse, which usually begins when the person is exposed to certain stimuli that he associates with drugs. It also implies that consumer behavior is maintained, even if it results in negative consequences for the person (Hyman & Malenkov, 2001).

It is even common for a vicious circle to be created: the individual consumes a substance, this directly and indirectly causes negative biopsychosocial effects, so that his escape route is to reuse it to escape problems.

Effects of drugs on the nervous system

1- DNA is altered

It seems that in the development of an addiction, transcription factors, immediate early genes and intracellular messenger pathways in the brain reward system are altered. It has also been observed that they affect the brain circuits involved in motivation, memory and decision making (Cadet, Bassano & Milroy, 2014).

However, how is the direct relationship of these systems to the abuse of addictive substances is not yet known with absolute certainty.

2- Alters the synaptic connections

In recent years it has also been shown that addiction changes the strength of synaptic connections of neurons, especially those that release and receive glutamate, an excitatory neurotransmitter (Harvard Mental Health Letter, 2004).

Numerous immunohistochemical, histological and morphometric investigations have been found in morphological variations in the brain of regular consumers of several different drugs.

Major findings include neuronal loss, generalized axonal damage, neurodegenerative problems, decreased gill fibrillary acidic proteins, and alterations in the cerebral microvasculature (Butter, 2011).

3 – Petrochemical and functional changes in the brain

According to Volker et al (2003), petrochemical and functional changes have been observed in the brains of addicts through neuroimaging studies.

When the person is under the effects of drugs or in the craving (strong desire to re-consume it) complex brain mechanisms are activated. These involve reward pathways (nucleus acumens), circuits associated with motivation (OFC), memory (amygdale and hippocampus) and cognitive control (cingulated gyros and prefrontal cortex).

4- Decreases dopamine levels

Other research has highlighted the role of dopamine, a substance that increases sharply and very rapidly when under the reinforcing effects of drugs.

According to a Harvard Mental Health Letter in 2004, it seems that the main mechanism that maintains the addiction is the release of dopamine into nucleus of acumens when the drug is consumed. This arouses pleasure in the subject and functions as a false signal, indicating that such behavior facilitates survival or reproduction.

This system is known as the reward path, and it facilitates the brain to record that experience to try to repeat it in the future.

Naturally, rewards are effortlessly earned and often delayed. However, with drugs, the opposite happens: access to pleasure is direct.

Therefore, when consumption is discontinued, the level of dopamine drops causing dysfunction in the prefrontal area of ​​the brain. This leads to impulsivity and problems for inhibitory control. There is also a reduction in the gratifying capacity of natural reinforcing stimuli, such as food or sex.

When a substance is abused for a long period of time, there is a decrease in dopamine levels in an attempt by the brain to regulate them. Addicts will gradually need higher doses and more often to get the effects that the drug produced at the beginning.

5- Raise the threshold of pleasure: loss of control

Volker et al (2003) proposed a model to explain the typical loss of control of addiction that consumers have.

They state that in this situation, the addictive substance and the stimuli that relate to it acquire a great power of reward that prevails above any other pleasant stimulus.

This is caused by conditioning and misalignment at the threshold of pleasure, so that the person gets accustomed to very high levels of pleasure produced by the drug and another stimulus is not able to provoke it.

In addition, when the subject is exposed to the drug or elements associated with it, it seems that the mere memory of the gratification provided by that substance produces over activation of the reward circuit while decreasing cognitive control.

That is why it is very difficult for addicts to inhibit their search behavior of the drug and to quit consumption.

Despite years of abstinence, memories remain fixed in the mind of the addict. In this way, before events, places or experiences that are related to the drug reactivate this desire to consume it, regardless of the time that has passed.

This phenomenon is called conditioned learning, which establishes very persistent associations between two stimuli, mainly when they involve ways of pleasure. This occurs because the nucleus acumens send signals to the amygdale and hippocampus, and these are dedicated to storing and consolidating memories that provoke intense feelings.

For this reason, an alcoholic who has not been drinking for years can feel the impulse to drink again when he returns to the bar he frequented before. Another example is what you can feel a former addicted to her0in when he sees a hypodermic needle.

That is why it is advised to avoid relapses in cases of addiction to change the environment and habits of the person. Since an addict will never stop being addicted.

In fact, external or internal tensions can encourage a relapse. That is, addicts are in situations that are sensitive or generate stress or discomfort.

Also Read: Social Media Addictions: How does it affect its misuse?

People who fall into addiction were probably already hypersensitive to stress or had difficulty tolerating frustration, characteristics that make them prone to initiate and maintain consumption. Although at other times, that altered response to stress can come from brain alterations after a long time of substance abuse.

The truth is that the level of corticotrophin-releasing hormone (CRH), which regulates stress and activity of the amygdale, has been shown to increase in addicted subjects before a relapse.


The main substances of abuse are alcohol, cannabis, opiates, cocaine, amphetamine, methamphetamine and ecstasy. Each drug will activate a biological process in a different way, also causing dopamine to invade the nucleus acumens (Harvard Mental Health Letter, 2004).

The World Drug Report (2015) states:  “It is estimated that a total of 246 million people, or one in 20 people between the ages of 15 and 64, used illicit drugs in 2013. […] The magnitude of the world drug problem becomes more evident if one takes into account that more than 1 in 10 drug users is a problematic consumer suffering from disorders caused by drug use. This puts a heavy burden on public health systems … Only 1 in 6 problem drug users in the world has access to treatment. “

According to the European Drugs Report 2015: “It is estimated that almost a quarter of the adult population of the European Union (more than 80 million people) has tried illegal drugs at some point in their lives. The most commonly used drug is cannabis (75.1 million), with estimates of cocaine (14.9 million), amphetamines (11.7 million) and MDMA (11.5 million) being lowest. “

In addition, it also indicates that “cannabis is the most frequently reported drug as the main reason to start drug treatment for the first time in Europe.”

Why do some people fall into addiction and others do not?

According to studies with adoptees and twins, approximately 50% of individual differences in the likelihood of falling into addiction are inherited.

Individual differences:

– Vulnerable reward system

– Response to intensified stress

– There are people who learn the addictive habit more quickly. This often occurs in people with depression, anxiety, personality disorders (borderline disorder or antisocial disorder) or schizophrenia.

– Operation of the prefrontal cortex: if it works incorrectly, the person may have problems controlling their impulses, making decisions and reflecting on future consequences of their actions. An ideal context for compulsive consumption.

Special care must be taken with adolescents, since the prefrontal cortex has not yet fully developed. That is why it is common for young people to behave at risk and experiment with drugs.

In recent years there is a debate about this, with the question of whether the maintenance of addiction is really for physiological reasons or is rather psychological.

It seems that it does not arise directly as the property of certain drugs, there being no addictive substances but addicted individuals. Proof of this is that similarities have been found between the brains of gambling addicts and drug addicts. In addition, new addictions arise every time in which the consumption of toxic substances is not involved.

Good examples would be addiction to shopping, video games, the internet, food, or sex.


The problems caused will depend on the type of drug consumed, the vulnerability of each person to develop certain disorders or conditions and the frequency and amount of their consumption.

– Generally, these drugs consumed in large amount cause neurological, psychiatric and cardiovascular problems such as ischemia and vacuities.

– Prolonged use of amphetamine, methamphetamine and MDMA has been associated with an increased risk of developing Parkinson’s disease.

Specifically, methamphetamine produces physiological effects such as headache, difficulty concentrating, abdominal pain, vomiting or diarrhea, decreased appetite, sleep disturbances, paranoid or aggressive behavior and psychosis.

If too much is consumed, hypertension, arrhythmia, subarachnoid hemorrhage, cerebral infarction, intracerebral hemorrhage, seizures or even coma may occur. Magnetic resonance imaging studies have found that this substance can alter the frontal areas and basal ganglia of the brain.

– If we talk about alcohol, it has been linked to a shorter life span.

– Nicotine, present in tobacco, acts on the central and peripheral nervous system. We found changes in breathing and blood pressure, constriction of the arteries, and increased alertness.

– As for cocaine, its consumption can induce hypertension and even lethal fever. It can also cause symptoms related to schizophrenia, such as paranoid ideation and visual and auditory hallucinations.

– Marijuana or hashish: it seems that they can trigger serious emotional disturbances or psychotic problems in subjects who are predisposed to them. If consumption begins before age 17, serious cognitive and neuropsychological disorders may develop.

However, their long-term damage is still being investigated as the repercussions are highly dependent on each subject.

Prevention and treatment

Treatment will depend on the type of addiction and also on the type of addict. For example, the same method cannot be used with an open-minded consumer and lack of inhibition than with people who are hypersensitive to stress.

As we have already mentioned, an addiction is chronic, so a continuous struggle is necessary. The person must be very convinced and motivated.

According to the model indicated above (Wallow et al., 2003), the best therapy should have a multidisciplinary approach, aimed at reducing the reinforcing power of drugs and improving the gratification of other alternative reinforces. It seeks to break with the conditioned associations learned and enhance cognitive control.