Additive Effects of Former Methylenedioxymethamphetamine and Cannabis Use on Subclinical Psychotic Symptoms

Methylenedioxymethamphetamine (MDMA) is an amphetamine-derived psychostimulant, usually known as "ecstasy." The long-term neuropsychological effects of MDMA are examined in several studies with conflicting results. The most common findings reported are depression, anxiety, and memory and attention deficits. In addition to acute psychotic reactions observed after MDMA use, serotonergic and dopaminergic toxicities may increase the psychosis risk in the long-term. Cannabis usage among MDMA users is very high. The aim of this study was, therefore, to examine the additive effects of cannabis and MDMA on subclinical psychotic symptoms (SPS).

Here, 131 healthy controls (hC), 54 former cannabis and MDMA users (C&M), and 46 former cannabis users (C) were evaluated for SPS. The definition of former user was based on the Munich Composite International Diagnostic Interview. The SPS scores were assessed by using the Schizotypal Personality Questionnaire (SPQ). The relationship between substance-free periods and total MDMA exposure with SPS was also examined.

The C&M group had higher levels of SPS than both C and hC groups. This is true not only for the total SPQ scores but both positive and negative schizotypy scores as well as cognitive-perceptual, disorganized, and interpersonal schizotypy scores aligned hierarchically in the 3 study groups (C&M>C>hC). The total MDMA exposure was positively correlated and MDMA-free period was negatively correlated with the SPS score.

We found that the former use of cannabis and MDMA is associated with marked elevation in SPS. Moreover, the exposure amount of MDMA and MDMA-free periods are important determinants of SPS. The longer the cannabis and ecstasy free periods, the larger is the waning of SPS.