Purpose: Neuroimaging; to investigate the effect of repeated ecstasy use on brain glucose metabolism as imaged through 2-[18F]-fluoro-2-deoxy-glucose (FDG) PET imaging. Specific hypotheses tested - That cumulative ecstasy dose would be related to changes in brain glucose metabolism, and that brain glucose metabolism would also be related to time since last ecstasy use and age of onset for ecstasy use.

Design: Retrospective (non-experimental) between-subjects design, with drug use (ecstasy user versus no reported ecstasy use) serving as a between-subject factor, with all participants receiving FDG PET scans. Subjects: 93 ecstasy users recruited at discotheques in the Hamburg (Germany) area and 27 oncology patients, presumably recruited through direct contact with researchers. Matching - Ecstasy users and non-user controls were matched on age and gender.

Criteria for Inclusion, Ecstasy Users - Using ecstasy at least once in a lifetime, no current alcohol abuse or dependence, and negative urinary tests for amphetamines, barbiturates, benzodiazepines, cannabinoids, cocaine metabolites or opiates on the study days, though trace amounts of urinary cannabinoids permitted on study days. Non-user controls - No past or current use of ecstasy or other illicit drugs, aged 30 or less, current cancer patient, no past or current major psychiatric disorders and no abnormal PET findings in the brain.

Drug Use Parameters - Ecstasy Use - Ecstasy users reported having taken 483 +/- 578 tablets over a lifetime (range: 1-3000). No information is provided concerning the frequency of ecstasy use per month. Time since last use, in days, was 192 +/- 429 days (Range: 3 days - 2880 days). Average duration of use was 38.4 +/- 25.2 months (range: 12 - 132 months) Age at first use of ecstasy was, on average, 19.5 +/- 3.5 years (range: 14-29 years old). No information provided on duration of use. Other Drug Use - Not reported in this paper.

Group Demographics and Matched Variables - Authors matched samples on the age and gender. Gender, as M/F ratio - Non-users, 13/ 14, ecstasy users = 50/43. Age - Average age of non-users was 24.1 +/- 4.2 years (range: 15-30 years), and average age of ecstasy users was 23.1 +/- 3.9 years (range: 18-37). No information is provided on education level attained in either group.

Measures: PET Scan - Scans were performed with 2[18F]-fluoro-2-deoxy-D-glucose (FDG), a radioactive tracer for glucose metabolism, and used a full-ring, whole-body system in 2-dimensional mode. All participants fasted 6 hours prior to scan. Ecstasy Users - 45 minutes after receiving 180-250 MBq FDG, ecstasy users received a 20-minute brain scan, with all participants requested to keep eyes open. Non-users - 40 - 60 minutes after receiving 300 - 400 MBq FDG, all controls received an 8-minute brain scan as part of standard protocol for the whole-body scan given to all oncology patients.

Volumetric Analyses - Brain structures selected for examination were: cingulate, Brodmann's Area 10, Brodmann's Area 11, caudate, putamen, amygdala and hippocampus. Voxel similarity between each participant's scan was compared to brain template. After transformation, FDG uptake in an individual scan was normalized to the average brain uptake for each participant in the 15% voxels with highest uptake. 'Hottest pixel analysis' was used to analyze maximum normalized FDG uptake within each volume of interest (VOI).

Hair Samples - Hair samples were collected from ecstasy users to corroborate reported drug use over

Analyses: PET Scans - Differences between FDG uptake in ecstasy users and non-users were analyzed via student's t test, with tests performed for equal and unequal variance using the Levene test, and with significance set at p. = .05. No adjustment was made for number of tests (i.e. Bonferroni corrections). Non-parametric Mann-Whitney U test was apparently used to examine comparison made via student's t test, perhaps only to those regions found to differ significantly across groups.

Drug Use Parameters and PET scans - The relationship between parameters of ecstasy use and differences in FDG uptake in specific brain regions was investigated through performing a 1-way, 2-tailed analysis of variance (ANOVA), presumably with drug use (ecstasy user versus non-user) serving as a between-group variable. Additionally, relationships between drug use parameters and amount of FDG uptake in apparently selected brain areas were analyzed via correlational analyses. Analyses were performed for cumulative ecstasy exposure (lifetime ecstasy dose), time since last dose, and age of onset for ecstasy use. Results - Significant Differences Found: PET scans - FDG uptake was significantly lower in the L and R putamen and caudate of ecstasy users, as compared with cancer patient controls. FDG uptake was also significantly lower in the L (but not R) amygdala of ecstasy users than in ontrols. The most prominent difference between ecstasy users and non-users was lower FDG uptake in the left caudate.

Drug Use Parameters and FDG Uptake - Global FDG uptake was more severely reduced in ecstasy users who first used ecstasy when younger than 18 years old. Time since last use of ecstasy was positively associated with FDG uptake in L cingulate and R amygdala, presumably with greater FDG uptake associated with longer interval since last use. Age of unset of ecstasy use was associated with reduced FDG uptake in L and R putamen, caudate, in L hippocampus and L Brodmann area 10 (unclear if age of onset for ecstasy use was associated with increased or decreased FDG uptake in Brodmann area 10, since ecstasy users had non-significantly elevated FDG uptake in this area).

Results - No Significant Differences: PET Scans - There was a statistically non-significant reduction in FDG uptake in the right amygdala and left hippocampus. While there were trends for ecstasy users to have lower FDG uptake in various areas (cingulate, Brodmann's area 11) and higher uptake in one area (Brodmann area 10), these differences were all non-significant. There was no single region of interest that could be used to differentiate all ecstasy users from all non-users on the basis of measured FDG uptake.

Drug Use Parameters and FDG Uptake - There was no association between (global) FDG uptake and cumulative ecstasy dose. Cumulative ecstasy use was unrelated to FDG uptake in cingulate, putamen, caudate, amygdala, hippocampus, Brodmann area 10 (all areas examined in correlational analyses). The effects of age of onset on FDG uptake were unaffected (not modulated) by cumulative ecstasy dose. There was a slight, but statistically non-significant, tendency for reduced FDG uptake in the caudate to be associated with higher cumulative (lifetime) ecstasy dose. There was a non-significant association between age of onset of ecstasy use and FDG uptake in L, R putamen, R cingulate, and L hippocampus, with lower age of onset associated with reduced FDG uptake.

Overall Effects: A sample of 93 male and female ecstasy users were found to have lower glucose metabolism bilaterally in putamen, caudate, and L (but not R) amygdala than a sample of 27 cancer patients, with brain metabolism assessed via FDG PET scan. The most prominent difference in ecstasy user FDG uptake was in left caudate, with ecstasy users showing lower uptake than controls. While FDG uptake differed in other areas, these differences did not reach statistical significance, and there was no single brain area whose FDG uptake distinguished all ecstasy users from all controls. Associations between time since last use and age of first ecstasy use (onset) and FDG uptake in specific areas were found, but analyses failed to find a relationship between cumulative (lifetime) ecstasy use and FDG uptake in any given brain area. Global FDG uptake was most reduced in participants whose first use of ecstasy occurred before age 18, with degree of global FDG reduction lessening as age of first use increased. FDG uptake in L cingulate and R amygdala increased as the interval between last ecstasy use and study day increased.

Comments: This paper appears to the second of two imaging studies performed by the same team and with the same sample of ecstasy users and oncology patients (see Buchert et al. 2001). However, this report differs from the earlier publication in that it presents results from correlational analyses of drug use parameters (lifetime use, time since last ecstasy use and age of onset for ecstasy use). This paper is notable for its failure to find an oft-reported relationship between lifetime (cumulative) ecstasy dose and any of the significant differences in FDG uptake in ecstasy users and non-user controls. This is unusual in that other studies have tended to find overall ecstasy dose to be associated with other between-group differences (McCann et al. 1998 with radioligand imaging; cognitive function, Croft et al. 2001; Gouzoulis-Mayfrank et al. 2000; Zankzanis et al. 2001). Furthermore, age of onset is not likely to be an indirect measure of cumulative ecstasy use in this sample because it is not correlated with cumulative ecstasy use. A stronger case can be made for serotonergic neurotoxicity on the basis of imaging studies using more direct markers of serotonin function than assessing glucose metabolism via FDG. This study is retrospective, compares polydrug users with non-drug using controls and relies on self-reported drug use history only, hence limiting the generalizability of study findings. Comparing FDG uptake in ecstasy users and cancer patients may underestimate differences between ecstasy users and non-users if life stress produced by cancer diagnosis also produces changes in brain FDG uptake. Future studies employing healthy, age-matched polydrug using controls might be able to better confirm or clarify the findings reported here.