Alcoholism is the well-known term used to describe a physical dependence on the (typically unrestrained) consumption of alcohol. Polysubstance or polydrug addiction is a lesser-known term used to describe a simultaneous addiction to at least two substances, including any combination of alcohol, illicit\/illegal drugs and mind-altering medications. In a study published in September 2014 in the journal Drug and Alcohol Dependence, a multinational research team used modern imaging technology to compare the changes in brain structure brought about by alcoholism to the changes in brain structure brought about by polysubstance addiction. Alcoholism Physical dependence occurs when an individual uses alcohol or a mind-altering drug or medication often enough and\/or in large enough quantities to make the brain reliant on continuing intake in order to function \u201cnormally.\u201d In the context of alcohol consumption, a physically dependent state is essentially synonymous with the presence of addiction, a condition characterized by clearly dysfunctional changes in brain function, as well as the establishment of a clearly dysfunctional pattern of day-to-day behavior. Some of the behavioral dysfunction found in people physically dependent on alcohol also typically appears in serious alcohol abusers who have no pressing physical need to drink. For this reason, doctors no longer treat alcoholism and alcohol abuse as separate physical\/mental problems. Instead, they diagnose alcohol use disorder, a condition that includes alcoholism, alcohol abuse and overlapping symptoms of alcoholism and alcohol abuse. In each individual case, the number of symptoms present indicates the severity of the disorder. Polysubstance Addiction Some substance abusers consume only one substance in excessive amounts. However, many affected individuals simultaneously consume at least two substances excessively. Public health experts and addiction specialists commonly refer to the simultaneous or overlapping abuse of two or more substances as polydrug abuse or polysubstance abuse. Any person who participates in polysubstance abuse runs the risk of developing an addiction to multiple substances (i.e., polysubstance addiction). Other well-established consequences of this form of substance abuse include heightened chances of experiencing a substance overdose, heightened chances of developing the severe cardiovascular (heart and blood vessel) complications associated with the abuse of certain drugs and medications, and heightened chances of developing mental\/emotional complications of substance abuse such as medically serious anxiety and the extremely dysfunctional state known as psychosis. Particularly dangerous combinations of substances include alcohol and opioid drugs\/medications, alcohol and amphetamines, and amphetamines and the drug MDMA (Molly, Ecstasy). Differences in Brain Effects In the study published in Drug and Alcohol Dependence, researchers from the U.S., Sweden, Poland and Ghana used an advanced form of MRI (magnetic resonance imaging) scanning to compare the brain structures of people affected by alcoholism to the brain structures of people affected by polysubstance addiction. They undertook this project, in part, because more than half of all people diagnosed with alcohol use disorder also misuse at least one illicit\/illegal drug or mind-altering medication. A total of 40 abstinent drinkers with alcoholism took part in the study; 19 abstinent substance abusers affected by polysubstance addiction also participated. In addition, the researchers looked at the brain structures of 27 casual drinkers not affected by alcoholism or polysubstance addiction. The researchers concluded that, compared to people affected only by alcoholism, people affected by polysubstance addiction have a significantly larger amount of brain material called white matter (which helps carry signals between active brain cells). This fact holds true even when polysubstance addicts consume roughly the same amount of alcohol as alcoholics. The researchers also concluded that, compared to people affected by polysubstance addiction, people affected only by alcoholism have a significantly smaller amount of brain material called grey matter (which is formed by active brain cells). Compared to light drinkers, people affected by polysubstance addiction have larger amounts of white matter and smaller amounts of grey matter. Compared to light drinkers, people only affected by alcoholism have a widespread deficiency of grey matter. The study\u2019s authors note the clear differences between the structural brain consequences of alcoholism and the structural brain consequences\u00a0of polysubstance addiction. The chief characteristic of the alcoholism-related differences is an abnormal decline in the brain\u2019s grey matter, while the chief characteristic of the polysubstance-related differences is an abnormal increase in the brain\u2019s white matter. The authors believe that these characteristic changes may indicate a need for condition-specific methods of offsetting the brain-related consequences of alcoholism and polysubstance addiction.