Purpose: Immunological; to examine basal immunological function in regular ecstasy users to see whether any long-term or residual effects on the immune system were present. Specific hypothesis tested - that repeated perturbation of cell-mediated immunity by repeated doses of MDMA taken over time might reduce effectiveness of cell-mediated immunity.

Design: Retrospective (non-experimental) incompletely crossed within-subjects / between groups design, with time of sample (baseline, l year post-baseline, 2 years post-baseline) serving as a repeated measure and drug use (ecstasy use versus no drug use) serving as the between-group measure, with all ecstasy users undergoing blood draws at baseline, 1 year post-baseline and 2 years post-baseline, and all non-drug user controls undergoing blood draws at baseline.

Subjects: 6 male ecstasy users and 8 non-drug using blood donors residing in or near Barcelona (Spain). Non-drug user controls were apparently recruited from healthy blood donors. No information is offered on recruitment method for ecstasy users, but past studies performed by this team have recruited people via word of mouth. Matching - Groups were matched on age and physiological characteristics.

Criteria for Inclusion - Ecstasy Users - Male, healthy, as determined via physical and psychiatric examination, with no current drug or alcohol dependence except for nicotine, reported having used ecstasy at least 5 times in lifetime, and abstinence from any psychoactive substance on the study day, with abstinence verified by urinalysis. Available for blood sample at 3 points in time over a 2 year period when trials taking place. Non-Drug Users - Never having used any illicit drugs, matched on age and physical characteristics, potentially being male, though information on the gender of non-drug using controls is not provided.

Drug Use Parameters - Ecstasy users in this sub-sample reported having used ecstasy on 5 to 50 occasions (range across all participants) at baseline; no other specific information is provided about drug use parameters in the sub-sample or the larger sample. No information is provided on average dose per use, frequency of use, duration of use or time since last use. Presumably time since last use was at least 1 day prior to study day, with abstinence verified via urinalysis. Other drugs - All ecstasy users used cannabis regularly, and at least some had used cocaine or methamphetamine at least once.

Group Demographics and Matched Variables - The authors matched samples for age and physiological characteristics, and possibly on gender. No specific information on demographic variables was provided for the 6 ecstasy users or the 8 non-drug using controls. For complete sample of 30 ecstasy users and 24 non-drug users. Gender - As M/F ratio, ecstasy users = 6/0, non-drug users = unknown, perhaps 8/0. Age - Average age of overall sample of ecstasy users (30) was 24 years (range = 20-36 years). Information not provided on mean age of non-drug using controls, though they were matched for age. Weight, in kg - (Overall sample) ecstasy users weighed, on average, 67.9 kg (range = 56.5-86 kg). No information provided on weight of non-drug using controls. Height, in cm - Average height of overall sample of ecstasy users was 175.4 cm (range = 167-189 cm.) No information provided about non-drug using controls. Education - No information on years of education attained in either sample.

Measures: Complete blood profile and cell count conducted on blood drawn from each participant at baseline, 1 year post-baseline, and 2 years post-baseline. Number of lymphocytes counted by cytometer. Immune cell types detected via dual-color immunophenotyping; cell counts were made for helper-inducer, cytotoxic-suppressor, natural killer, mature B and T lymphocytes.

Analyses: Differences between immune cell counts in ecstasy users and controls were examined via 1-way analysis of variance (ANOVA), with drug use (ecstasy use versus no drug use) serving as a between-groups variable. Separate analyses were carried out for cell counts taken at baseline, 1 year post-baseline and 2 years post-baseline, with each sample compared with control cell counts. Probability value was set at 0.05. If there were changes in cell count, multiple comparisons (across time) were carried out using Tukey's test.

Results - Significant Differences Found: While baseline counts of total lymphocyte numbers did not differ between ecstasy users and controls, total number of lymphocytes was lower in ecstasy users 1 and 2 years post-baseline. Comparing cell counts over time, total number of lymphocytes 2 years post-baseline was also significantly lower at 2 years post-baseline than it was at baseline, or 1 year post-baseline, indicating that total number of lymphocytes decreased in ecstasy users over time. Ecstasy user CD4 cell counts taken 2 years post-baseline were lower than CD4 counts from controls. CD4 cell counts declined in ecstasy users over time; CD4 count was lower 1 year post-baseline than at baseline, and CD4 count 2 years post-baseline was lower than at 1 year post-baseline. Ecstasy users had lower CD 19 B cell counts than non-drug user controls at 2 years post-baseline. B cell count 1 year after baseline was significantly lower than B cell count at baseline for ecstasy users, and B cell count 2 years post-baseline was lower than at 1 year post-baseline. Ecstasy users had lower NK cell counts than non-drug using controls at all time points measured (baseline, 1 year post baseline, 2 years post baseline).

Results - No Significant Differences: Ecstasy users and non-drug user controls had similar numbers of total lymphocytes, CD4 counts, CD8 cells and CD19 cells at baseline. A year after baseline, ecstasy users and non-drug user controls still had similar CD4, CD8 and B cell counts. CD8 counts taken 1 year post-baseline did not significantly differ from those of controls, or from baseline counts in ecstasy users. Baseline numbers of CD19 B cells were similar to those of non-drug users. Ecstasy users' NK cell counts performed 1 or 2 years after baseline did not significantly differ from baseline NK cell count. Overall Effects: As was the case with the larger sample of ecstasy users and controls, a small number of ecstasy users drawn from this sample had lower NK cells than controls at baseline without there being any other differences in cell count. However, when cell counts were performed 1 year after baseline, total number of lymphocytes were now significantly lower than lymphocyte numbers in non-drug using controls. 2 years after baseline, ecstasy users had fewer total lymphocyte numbers, CD4 cells and B cells than controls - only numbers of CD8 cells did not decline over time. NK cell counts were lower in ecstasy users than in controls at all points in time, including 1 year and 2 years after baseline. Hence it would appear that presumed continued use of ecstasy over a 2-year period disrupted cell-mediated immune function, particularly in the case of NK cells. The authors note that some immune functions, including T-cell production, are reliant on serotonin, and so it is possible that reduced CD4 cells result from reduced serotonergic function. However, they also note that there may be other reasons for changes in cell-mediated immunity, including chronic exposure to other acute effects of MDMA, or the use of other drugs. The authors' hypothesis was confirmed, since continued use of ecstasy over time appears to affect reduce numbers of several types of immune cell.

Comments: To date, this is the first report of long-term effects on cell-mediated immunity in regular ecstasy users. Findings can only be considered preliminary, considering the extremely small sample size used in this study, but the findings do suggest that further research in humans and in non-human animals might prove fruitful. Since the data was presented in a review article, a number of potentially important characteristics of both samples were not fully reported. This information may well appear in future publications presenting this original research in more detail. In addition to the limitations relating to the larger study (small sample size, retrospective design, failure to control for use of other drugs), ecstasy use over the time period tested is not reported. Without more information on the amount of ecstasy consumed in the time between each blood draw, it is unclear whether changes in cell count result from continuing use of ecstasy. a past history of ecstasy use, or neither of these causes. However, these preliminary findings suggest that regular ecstasy use may place someone at risk for contracting an infectious disease, though apparently the risk is not extreme.