2000 - Gouzoulis-Mayfrank Memory Study
Impaired cognitive performance in drug free users of recreational ecstasy, Journal Neurol Neurosurg Psychiatry Vol 68, June 2000, 719-725

28 MDMA users who had also used cannabis extensively and who were asked to remain MDMA free for 3 weeks were compared with matched groups of cannabis smokers and non recreational drug users on a series of tests. The tests were things like attention response (look at a computer screen and hit keys based on what patterns appear) in a range of complexity, short term memory tests like remembering lists of letters, and general intelligence & knowledge tests.

The MDMA users scored lower on several of the measures (see table 3) than either the cannabis smokers or the non drug users. On most tests, cannabis-only users scored better or equal to controls. On a few tests, the MDMA users scored better than controls, but on the short term memory tests the MDMA users scored consistently lower than non users. On the attention and quick-response tests, the MDMAusers scored slightly worse than the controls (10% or so meaning for these tests 40-50milliseconds or 1/20th to 1/25th of a second slower, on average). The researchers report that the MDMA users score slightly lower on the 'general intelligence' tests. The researchers conclude that the MDMA users have experienced 'neurotoxicity'.

2000 - Wareing Memory Study
Working Memory Deficits in Current and Previous Users of MDMA, British Journal of Psychology Vol 91 (No 2) May 2000, 181-188

This study involved 10 current ecstasy users, 10 previous users (last ingestion at least 6 months prior), and 10 controls who reported never haven taken MDMA. The researchers's primary tests were an 'executive function' test which involved asking the subjects to name 100 consonants, not in order, with as few repetitions as possible, an 'information processing speed' test which had the subjects mark lists of letters as 'same' or 'different' as fast as they could, and a test for anxiety in the test circumstances. 2 of the 10 previous users were unwilling to complete the fastest of the 'executive function tests' and both MDMA using groups scored much lower on the random-letter task than the controls. On the information processing task, the differences between groups were minimal and questionable. For the anxiety questionairre, the MDMA users responded to questions indicating that they were more anxious in the lab setting than the non users.

2000 - Reneman Memory Study
Memory disturbances in "Ecstasy" users are correlated . . . , Psychopharmacology Vol 148, 2000, 322-324

This study looked at 5 MDMA users and 9 non-users. The MDMA users had taken an average of 218 MDMA tablets in their lifetime (ranging from 50-500 tablets) and were required to abstain from psychoactive drug use for 2 months prior to the study. Each participant was given a word-recall memory test (RAVLT), and the next day a sensitive brain scan (SPECT- single photon emission computed tomography). The researchers report that scans of the MDMA users' brains reveal significantly different levels of 5-HT2A (serotonin) binding in two of the 5 brain areas examined. They also report that the MDMA users scored much worse on the memory test.

1999 - Dafters Cognition Study
Level of use of MDMA in humans correlates with EEG power and coherence, Psychopharmacology Vol 145, 1999, 82-90

The researchers looked at 23 MDMA users using EEG measurements of brain waves and a battery of cognitive and mood tests. The researchers were trying to determine if MDMA-related brain changes could be detected using the relatively simple EEG (compared to extremely expensive MRIs and radioactive injection for tomographic scans). They found that a higher level of historical use of MDMA in the subjects was associated with measurable differences in alpha (8-12Hz) and beta (12-20Hz) but not in delta (1-3Hz) or theta (4-7Hz). The researchers also found no correlation between the mood and cognitive tests they gave and MDMA use.

1999 - McCann Cognition Study
Cognitive performance in (+/-) 3,4-methylenedioxymethamphetamine (MDMA, "ecstasy") users: a controlled study, Psychopharmacology Vol 143, 1999, 417-425

This study gave a battery of mental challenge tests to 22 MDMA users and 23 controls and measured their serotonin metabolite levels using a spinal tap. They also administered a wide range of physical and mental tests, psychiatric interviews, pain testing, sleep studies, and others. The researchers reported that while "MDMA users and controls were found to perform similarly on several cognitive tasks...MDMA subjects had significant performance deficits" on several sustained-attention tasks. The researchers also found that the MDMA using group had lower serotonin metabolite levels than controls.

1999 - Morgan Memory Study
Memory Deficits associated with recreational use of ecstasy (MDMA), Psychopharmacology Vol 141, 1999, 30-36

This study into the possible medium/long term memory effects of MDMA attempts to tease apart the effects of MDMA use from other types of drug use. There were three groups of test subjects: 25 MDMA users, 22 poly-drug non MDMA users, and 19 "non drug using" controls (only alcohol and cigarette use). All MDMA users had used MDMA on at least 20 occasions. The participants were given story recall tests to test both immediate and delayed memory. Even though all three groups were matched for education level, the MDMA users performed worse on the memory tests than both the control group and the poly drug using group.

1998 - Bolla Memory Study
Memory impairment in abstinent MDMA ('Ecstasy') users, Neurology Vol 51, Dec 1998, 1532-1537

This study gave a series of standardized memory tests to 24 control subjects and 24 frequent MDMA users. The MDMA users had taken MDMA an average of 60 times (2x per month) at an average dose of 158 mg, and were required to abstain from any drug use for 2 weeks prior to the study. The MDMA users scored lower on some tests and higher on others. The researchers focused on the areas where scores were lower (verbal and visual memory), but the results seem inconclusive.

1998 - Parrott Cognition Study
Ecstasy (MDMA) effects upon mood and cognition . . ., Psychopharmacology Vol 139, 1998, 261-268

This study is an attempt to look at real-world clubbing and the effects of ecstasy use on cognitive test scores. Three groups of volunteers (15 'regular' ecstasy users with more than 10 uses, 15 'novice' users with less than 10 uses, and 15 controls who had never taken MDMA) were given cognitive, memory, and mood tests before, during, and after a Saturday night at a club. MDMA was ingested by all 30 'users' and a variety of other substances were ingested by both 'users' and controls. The researchers report that the regular MDMA users scored worse on most of the cognitive/memory tests than the contorl group.

1999 - Hatzidimitriou Neurotoxicity Study
Altered Serotonin Innervation Patterns in the Forebrain of Monkeys Treated with MDMA . . ., The Lancet Vol 352, Oct 31, 1998, 1437

This is the second half of a study begun in 1992. Squirrel monkeys were given a sub-cutaneous injection of 5/mg per kg of MDMA twice a day for 4 days. The original study looked at the affect of MDMA on the 5-HT receptors up to 18 months after use. This study looked again 7 years later to try to determine the degree of recovery of the receptors. It found some, but not complete, recovery.

1998 - McCann Neurotoxicity Study
Positron emission tomographic evidence of toxic effect of MDMA . . ., The Lancet Vol 352, Oct 31, 1998, 1437

This 1998 study compared 14 heavy MDMA users with 14 control subjects. They used sophisticated PET scans to try to measure the amount of serotonin axons in each subject. It found that heavy MDMA users (500 mg average dosage between 70 and 400 times) tended to have somewhat lower serotonin axon counts. No behavioral or functional impairment was found in these users.

1999 - McElhatton Birth Defect Survey
Congenital anomalies after prenatal ecstasy exposure , The Lancet Volume 354 (No 9188) October 23 1999

This 1999 Survey looked at the outcome of 136 pregnancies in mothers who reported using Ecstasy during pregnancy. They found a higher than average number of congenital birth defects in the 78 babies which were born. However, the study looked only at the 136 MDMA exposed women (out of 302) who continued with follow-up treatment after birth, which leaves open the possibility that the data is skewed towards those who experienced some sort of problem with the birth.