Marijuana: dose effects on pulse rate, subjective estimates of intoxication, free recall and recognition memory

The effect of marijuana on memory as measured by free recall and recognition, pulse rate and self ratings of intoxication was evaluated in 16 male volunteers. Marijuana containing 0, 5, 10 or 15 mg delta9-THC was administered to all subjects by smoking in 4 sessions separated by a 1 week interval. Free recall was reduced in a dose related manner by the drug, but recognition memory was unaffected. A 2 sec word presentation rate produced inferior recall in comparison to a 4 sec rate, but this variable did not interact with drug condition. Intrusion errors increased following intoxication but this effect was not systematically related to dosage of delta9-THC. Both pulse rate and self ratings of intoxication increased with dosage.