Effects of acute and chronic inhalation of hashish, marijuana, and delta 9-tetrahydrocannabinol on brain electrical activity in man: evidence for tissue tolerance.

An EEG profile for cannabis preparations equated for delta 9-THC activity has been defined in occasional cannabis users in New York and in long-term, high-dose hashish users in Athens. The EEG effects of enhanced alpha activity, decreased beta activity, and decreased mean frequency are dose dependent, both in intensity and in duration. The behavioral measures, particularly self-ratings of euphoria ("high" or "mastura") and heart rate, are also dose dependent and interrelated with the EEG measures. Tolerance to the cerebral, heart rate, and behavioral effects of repeated inhalations of delta 9-THC are demonstrable in chronic users and also in short-term (21-day) experimental administration studies. delta9-THC and cannabis preparations are distinguishable from opiates, hallucinogens, and deliriants by their EEG effects. No differences in incidence of abnormal EEG records were found between long-term heavy hashish users and controls. Taken in conjunction with the neurologic, echo-EEG, and psychopathologic data in these men, we failed to define a syndrome of persistent brain damage as a result of hashish use, although persistent adaptational changes are noted in the development of tissue tolerance.