No one can deny that drugs have a range of effects on the body and, in particular, on our nervous system. Typically, people who use these substances are seeking to experience the effects these drugs provide. Although in the short term these effects may seem pleasurable, continued use of a drug can lead to very harmful consequences for the nervous system. What specific effects does drug use have on the brain?
Direct effects on the nervous system
Drugs have several effects on the nervous system. Some of the main ones are:
- Functional and neurochemical changes in the brain
Some experts on the effects of drugs on the brain state that the use of these substances causes neurochemical and functional changes in the brain. When a person is under the effects of drugs or experiencing craving (an intense desire to use again), complex brain mechanisms are activated. These affect reward pathways and circuits associated with motivation, memory, and cognitive control.
- Disruption of synaptic connections
One factor that has been studied and confirmed in recent years is how an addiction can change the strength of synaptic connections between neurons, especially those that release and receive glutamate, an excitatory neurotransmitter. Among other harms, neuronal loss and neurodegenerative problems have been observed.
- Reduced dopamine levels
Other studies highlight the role of dopamine in the brain. This substance rises sharply and very quickly when a person is under the effects of a drug. According to studies, the main mechanism that sustains addiction is the release of dopamine when using. This produces pleasure in the addicted person and acts as a false signal indicating that this behaviour supports survival or reproduction.
This system is what we call the reward pathway. It records in the brain the memory of the pleasurable effects of the drug so it can be repeated in the future. Naturally, rewards are achieved through effort and usually take time. With drugs, however, the opposite happens: access to pleasure is direct. As a result, when use is interrupted, dopamine levels drop, causing dysfunctions in the brain.
Another related effect is a reduced ability to feel satisfaction from natural stimuli such as food or sex. On the other hand, when a person abuses a substance over a long period of time, dopamine levels fall. This is what the brain does in an attempt to regulate these levels. That is when the factor of tolerance appears: the addicted person will gradually need higher doses, and more frequently, to achieve the effects the drug produced at the beginning.
- DNA alteration
In the development of an addiction, it appears that elements of DNA in the brain’s reward system are altered. An impact on brain circuits involved in motivation, memory, and decision-making has also been observed. Despite this, it is still not known with certainty what the relationship is between these factors and the abuse of addictive substances.
- Increased pleasure threshold
The pleasurable effects produced by the drug prevail over any other pleasant stimulus. This occurs due to imbalances in the pleasure threshold. The addicted person has become accustomed to very high levels of pleasure produced by the substance, and no other stimulus is able to provoke it. This makes even more sense when the person is exposed to the drug or elements associated with it. The memory of the satisfaction produced by the drug overactivates the reward circuit and also reduces cognitive control. That is precisely why it is very difficult for an addicted person not to be focused on whether they have access to the substance and to stop using.
Another important aspect is that, although an addicted person may have several years of abstinence, memories of use remain imprinted in their mind. Places or experiences related to the drug can reactivate the desire to use it, despite the time that has passed. For example, a person with alcoholism who has gone years without drinking may feel the urge to drink again when they return to the bar they used to frequent. Or, for example, a former heroin addict may feel the same if they see a hypodermic needle.
Effects by type of drug
The effects that drugs have on the body are not the same depending on which one is used. The WHO classifies these substances into three types: stimulants, depressants, and hallucinogens.
- Stimulant drugs
These substances speed up the brain’s normal functioning, causing a state of activation. The effects of stimulant drugs are:
- Disinhibition
- Euphoria
- Reduced fatigue and sleep
- Poor emotional control
- Irritability and aggressiveness
- Restlessness
- Motor excitation
There are three types of stimulant drugs that produce these effects. On the one hand, there is cocaine, which suppresses sensations of tiredness, sleep, and hunger and enhances alertness and strength. Then there are amphetamines, which cause feelings of alertness, euphoria, or increased activity, as well as loss of sleep and appetite. Finally, there is tobacco and its active ingredient, nicotine, whose effects are a combination of stimulant and depressant effects.
- Depressant drugs
These substances are characterised by depressing and slowing down the central nervous system. This causes a general and progressive numbing of the brain. The effects of depressant drugs are:
- Calmness and relaxation
- Well-being and inner peace
- Apathy
- Sedation
- Reduced tension
- Harmony with oneself
Depressant drugs are classified into three types. First, there is opium and its derivatives such as heroin or methadone. They produce, among other things, relaxation, indifference, and an inability to concentrate. Second, there is alcohol and its derivatives. At low doses, the effects are euphoria and disinhibition. At higher doses, the depressant effect increases and can cause sleep, coma, and cardiorespiratory arrest. Finally, there are hypnotics and sedatives, whose effects are relaxation and drowsiness.
- Hallucinogenic drugs
Also called disruptive drugs, these drugs are characterised by altering perception and sensations. Their effects are:
- Changes in mood
- Changes in thinking
- Altered state of consciousness
This type of drug is classified into two types. On the one hand, there is cannabis, which causes relaxation, reduced memory and attention span, hilarity and, to some extent, confusion and drowsiness. On the other hand, there are hallucinogens, which disrupt the interaction between nerve cells and serotonin. In this sense, they produce hallucinations and delusions, alter mood and behaviour, and cause hyperactivity and mental confusion.
