Scientists have studied both long-term and short-term effects of drugs on the brain, and while there are still many things they do not know, they have learned that drugs have a direct and powerful impact on the brain’s functioning. Drugs disrupt the natural chemical balance of the brain, and many of drugs’ harmful effects are long-lasting and extremely difficult to overcome.How Drugs WorkNeurons in the brain communicate with each other by releasing chemicals called neurotransmitters that travel from one neuron to another neuron’s receptor.
Each chemical fits into its matching receptor, much as a key fits into a lock. The way that heroin and other opiates work is by mimicking endorphins, thus fitting into the endorphin receptors. This causes the same pleasurable feelings that endorphins create. Marijuana also operates in a similar manner. Cocaine and methamphetamine, on the other hand, work by causing the body to produce excess amounts of dopamine.
Neurons have structures called transporters whose function is to recycle released neurotransmitters, storing them for later use. Cocaine works by blocking these transporters, preventing them from recycling dopamine back into the cells, and creating an overabundance of dopamine in the brain. Methamphetamine similarly blocks these transporters, but it also causes the neurons to release additional dopamine, saturating its receptors.
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The Effects on the Brain
As the brain is continuously flooded with neurotransmitters, it adapts to the change. As a result, the brain begins to show a tolerance for, and dependence on, the drug. Larger amounts of the drug are needed to achieve the same effect. Eventually, the brain will stop producing dopamine or endorphins completely, making it increasingly difficult to experience any pleasure at all and leading to extreme depression and anxiety. When a heavy heroin user stops taking the drug, endorphin production is suddenly restarted, causing a chemical imbalance that affects the nervous system.
This leads to physical withdrawal symptoms such as nausea, muscle spasms and diarrhea. Generally, these symptoms will have stopped after ten days, as the body restores its equilibrium.Although withdrawal from cocaine and methamphetamine is not as physically noticeable, consequences can be longer lasting. In the case of methamphetamine, in particular, the brain is subjected to long term-trauma. Both the structure and function of the brain are changed.
First of all, dopamine receptors and transporters are damaged or destroyed by the large amounts of dopamine released. Brain imaging has shown that serious methamphetamine users have, on average, 24 percent fewer dopamine transporters than those who have never tried the drug. Over time these tissues can regrow.
Methamphetamine also affects the part of the brain that controls cognitive processes. Dr. Nora Volkow, Director of the National Institute on Drug Abuse, examined brain scans of methamphetamine abusers who had been abstinent for 14 months. The scans showed that they had regrown most of their dopamine receptors; however, the part of the brain that controls cognitive abilities showed no improvement. The former users still exhibited noticeable impairment in motor skills, judgment and memory.There are other studies, however, that have shown significant, though gradual, recovery for methamphetamine users who have stopped using for at least one or two years.
These studies showed that some of the effects may be reversible, and many participants showed improvements in motor skills, memory and impulse control. What is known for certain is that the process is not a quick one and that both physical and behavioral therapy is often needed to facilitate recovery.