The use of alcohol and drugs can have both acute and chronic effects in the central nervous system, endocrine system, and other systems in the body. Changes can be structural and functional and have adverse effects on one’s health and quality of life. The fact that addiction is defined as a disease, and that it fits so well into this conceptual model, stems from the presence of these adaptations both structurally and functionally.

These adaptations are commonly viewed as tolerance and withdrawal; both common in individuals with prolonged usage of addictive substances. Tolerance is defined as a decrease in response to a chemical with usage over time, at which point increased amounts are necessary to obtain the desired effects. Withdrawal occurs when there is a lack of the chemical within the system and therefore somatic and psychosomatic symptoms occur. The types of symptoms are specific to the type of the withdrawn substance.

The cause of all of this occurs at the cellular and molecular level. Neurons work by sending signals back and forth in the CNS (central nervous system) and PNS (peripheral nervous system). These signals are positive charges called action potentials that occur in the neural cell with the influx of Na (sodium) and efflux of K (potassium). Intracellular communication of these neurons occurs at the synaptic cleft. It is here that the presynaptic neuron releases neurotransmitters that bind to receptor sites on the postsynaptic neuron causing excitation to occur in the postsynaptic neuron.

Prolonged use of alcohol and drugs can have adverse effects on the receptor site density on these neurons and is seen as tolerance and withdrawals in addicts and alcoholics when available neurotransmitters are decreased through decreased use of the drug of abuse. These structural changes to the cell are what the addict and/or alcoholic experience as both tolerance and withdrawal. It is important to note that not only does this disrupt homeostasis throughout the bodies systems but it also decreases the individual’s cognitive functioning; most notable being that of the prefrontal cortex. In reference to the brains functions, lack of cognitive ability means a decrease in reasoning, therefore an increase in poor decision making and a high likelihood of alcohol and/or drug use or relapse.

Physical aspects of alcohol and drug addiction are some of the initial hurdles an individual must get over as they begin their treatment. The good news is that the majority of structural and functional changes revert back to normal with enough time without alcohol and/or drugs; this means cognitive functioning and good decision making will increase over time in a rehab program. Because of a deviation in the system, other effects of chronic chemical use can occur including chemical imbalance causing depression, anxiety, insomnia, etc… and changes in the hedonic set point affecting an individual’s quality of life and ability to deal with stress and emotion.