Study shows meth users have lower empathy and higher aggression, ecstasy users show normal empathy but more impulsive aggression

By Dr. Chinta SidharthanReviewed by Susha Cheriyedath, M.Sc.Apr 23 2024

In a recent study published in the journal European Neuropsychopharmacology, a team of European scientists compared the behavioral profiles, including aggression and social cognition, of methamphetamine or “crystal meth” users and 3,4-methylenedioxymethamphetamine or “ecstasy” users to understand the distinct psychotropic effects of these two neurochemicals.

Study: Chemical cousins with contrasting behavioural profiles: MDMA users and methamphetamine users differ in social-cognitive functions and aggression. Image Credit: Srdjan Randjelovic / Shutterstock

Background

The use of drugs, especially methamphetamine, also known as METH, and 3,4-methylenedioxy-methamphetamine or MDMA, is rapidly becoming a health concern across Europe and the world. Statistics indicate that in 13% of the countries in the world, the drug most frequently used by individuals enrolled in drug treatment programs is METH. Furthermore, even with the coronavirus disease 2019 (COVID-19) associated disruptions to socializing and nightlife, the usage of MDMA has increased in the last few years, especially among young adults and adolescents.

Given the rapidly increasing use of these amphetamines, it is important to understand their harmful effects on cognitive health. While studies have shown that both these substituted amphetamines cause impairments in declarative memory and impulse control, these two chemicals do exhibit different cognitive profiles. These differences are believed to be partly due to their chemical structures. METH and MDMA also differ in their affinities to various types of monoamine transporters. These differences translate to variations in neurochemical responses that differently influence social cognition.

About the study

In the present study, the researchers aimed to understand the varying chronic effects of MDMA and METH on social cognition by using a slew of socio-cognitive tasks to compare individuals who used purely MDMA or were chronic METH users with a control group that was stimulant naive. Understanding the long-lasting effects of METH or MDMA use is vital since disruptions in socio-cognitive functioning can impact not just the decision-making and interpersonal relationships of substance users but also the outcomes of drug treatments.

The scientists conducted a case-controlled cross-sectional study to compare among chronic METH or MDMA users and controls naive to drugs. Quantitative hair analysis was used to assess the substance abuse of participants in the previous months and to control for the use of multiple stimulants.

Previous studies have reported that long-term use of METH has been linked to impairments in emotional recognition and empathy, and chronic use of METH is also known to decrease the ability to recognize anger and fear. Furthermore, self-reports from METH users indicate an increase in passive-aggressive behavior and aggressive and angry responses to emotional stimuli.

In contrast, studies reported that MDMA increases emotional openness, promotes pro-social and empathogenic behavior, and increases the inclination to be involved in social activities. Controlled laboratory studies have also found increased emotional empathy associated with MDMA use.

Given this evidence, the researchers hypothesized that chronic METH users would have socio-cognitive impairments and lower emotional and cognitive empathy and display aggressive behavior. In contrast, chronic MDMA users would display increased cognitive empathy, while their aggression and sensitivity to emotion recognition would not be affected.

The Multifaceted Empathy Test assessed Emotional and cognitive empathy, while the Face Morphing Task was used to determine emotional sensitivity. The Competitive Reaction Time Task was also used to evaluate aggressive social behavior.

Results

The results showed that emotional empathy and cognition towards positive stimuli were indeed lower among chronic METH users. Furthermore, they showed increased punitive and aggressive social behavior irrespective of provocation. Compared to stimulant-naive controls, chronic METH users also had heightened anger.

In contrast, chronic MDMA users exhibited higher punitive behavior only when provoked in comparison to controls. However, the correlation analysis suggested that lower cognitive empathy might be linked to higher hair concentrations of both METH and MDMA. Furthermore, an increase in the long-term use of MDMA was found to be linked to higher punitive behavior tendencies.

The findings confirmed the researchers’ hypotheses that chronic use of METH would increase empathy deficits and elevate aggression, while the long-term chronic use of MDMA would be linked to an increase in impulsive aggression. The dependence of METH on the dopamine transport pathways is believed to contribute to the deficits in socio-cognitive function observed in chronic METH users.

Conclusions

Overall, the findings suggested that chronic and long-term use of methamphetamine resulted in lower emotional and cognitive empathy and an increase in punitive aggression, while long-term MDMA use was found to increase punitive behavior only in response to provocation. However, contrary to previous studies, MDMA use was not found to heighten cognitive empathy, and the study found that emotion sensitivity and cognitive empathy both remained unaffected with persistent MDMA use.