Aims Cell-mediated immune function and the occurrence of mild infectious diseases was investigated.
Participants Polydrug consumers of 3,4-methylenedioxymethamphetamine (MDMA) and cannabis (n = 37) compared to cannabis users only (n = 23) and control group (n = 34).
Design A longitudinal prospective study with three cross-sectional evaluations at time 0 and at 6 months and 1 year was performed.
Findings At baseline, a significant decrease in interleukin (IL)-2 and an increase in anti-inflammatory transforming growth factor (TGF)-β1, together with a decrease in the number of total lymphocytes, CD4 and natural killer (NK) cells were observed in the MDMA–cannabis group, with intermediate alterations in the cannabis group. Immune alterations observed at baseline were sustained over time. No differences were found between regular and occasional MDMA users. A significantly higher rate of mild infections in regular MDMA–cannabis users compared with occasional MDMA–cannabis users and the remaining groups was observed.
Conclusions The present data confirm that long-term alterations in immunological homeostasis may result in general health status impairment and subsequent increased susceptibility to infection and immune-related disorders.