How Some Drugs Affect the Electroencephalogram (EEG)

The effects of drugs on the EEG vary and are often dose dependent. In general, drugs effects on the EEG are fairly predictable and include: no effect, accentuation of beta activity, background slowing with decreased amplitude and/or frequency of the alpha rhythm, intermixed theta and/or delta activity, decreased seizure activity, and lowering of the seizure threshold with increased spike and wave discharges. In severe overdose cases, the EEG may demonstrate alpha/theta coma, burst suppression, or even a "flat" EEG pattern.