Quantitative electroencephalographic differences associated with alcohol, cocaine, heroin and dual-substance dependence.

Resting electroencephalographic (EEG) activity was evaluated in 88 drug-dependent inpatients, abstinent 1-6 months, and 14 non-drug-dependent controls. The patients were assigned to one of four groups using DSM-III-R criteria: alcohol-dependent (n = 12), cocaine-dependent (n = 21), heroin-dependent (n = 19), or dual alcohol- and cocaine-dependent (n = 36). The analysis revealed significant differences between the five subject groups in high- and low-frequency beta power, but not in other frequency bands. Beta power was significantly greater in the alcohol-dependent and cocaine-dependent groups relative to non-drug-dependent controls. These group differences did not correlate with quantity/frequency measures of alcohol or cocaine use, family history, personality, mood, or demographic characteristics. The similar increases in EEG beta found in alcohol- and cocaine-dependent patients do not suggest a direct drug effect. Rather, they suggest the existence of a common premorbid variable or a complex interaction between alcohol/drug use and other variables.