Abuse of any type of drug, regardless of whether the drug is legal or illegal, can have an effect on the nervous system. The nervous system consists of the brain, spinal cord, nerve fibers and specialized nerve cells throughout the body. Drugs that interact with the brain can cause problems with sending or receiving signals in the nervous system.
Drugs that act as stimulants elevate mood and increase energy in the user, according to the National Institute on Drug Abuse. In the case of some stimulants, like methamphetamine and cocaine, the “high” is obtained by blocking the uptake of dopamine by neuronal cells. Dopamine is a chemical in the body that is responsible for helping control movement, emotions and the feelings of pleasure and pain, notes the University of Texas Addiction Science Research and Education Center. But illegal drugs aren’t the only common stimulants. Caffeine, often referred to as the most common drug in the world, can be abused just like any other drug. Caffeine interacts with neurotransmitters that affect the heart rate and other bodily processes.
While stimulants increase mood and alertness, depressants tend to give the user a feeling of drowsiness and decreased activity. The Partnership for a Drug Free America recognizes barbituates, benzodiazepines, alcohol and marijuana as types of depressants. Like stimulants, depressant drugs affect neurotransmitters. Gammaaminobutyric acid, or GABA, is a chemical that decreases brain function. Depressant drugs increase the occurrence of GABA, giving the desired effects.
Opiate and opiate-based drugs such as codeine, morphine and hydrocodone bind to opioid receptors throughout the body. When bound to these receptors, feelings of pain are reduced. When used by prescription and under the supervision of a doctor, opiates provide very effective pain relief. However, extended and uncontrolled opiate use causes an individual to become immune to the effects, and more of the drug is required to illicit the same effect. When abused, addiction occurs, and the user can become dependent on the drug to maintain basic daily function.
Patients with bipolar disorder or schizophrenia often receive antipsychotic medications. Antipsychotic drugs can help to reduce the occurrence of hallucinations and delusions due to psychosis by reducing the function of the binding sites for the neurotransmitter dopamine. According to The Merck Manuals Online Medical Library, excessive activity in cells which have dopamine receptors appear to be one cause of psychosis.