Socio-cognitive functioning in stimulant polysubstance users.
Using more than one psychotropic substance is accompanied by increased risks for psychiatric and physical disorders. Accordingly, deficits in basal cognitive functions have been consistently associated with polysubstance use (PSU), whereas little is known about potential impairments in more complex socio-cognitive skills, which are relevant for daily-life functioning. Therefore, we investigated the effects of toxicological validated stimulant PSU on social cognition under consideration of potential cumulative effects. We compared socio-cognitive performances of 47 individuals with stimulant PSU with 59 matched stimulant-naïve controls using the Multifaceted Empathy Test (MET) and the Movie for the Assessment of Social Cognition (MASC). Additionally, social network size was assessed by the Social Network Questionnaire (SNQ). Hair and urine testing was employed to categorize three PSU subgroups (3, 4, and ≥5 substances used) and to ensure drug abstinence in controls. Individuals with stimulant PSU showed lower emotional empathy (MET) and a smaller social network (SNQ) compared to controls (both with linear trends for increasing number of used substances: p < .05). In contrast, cognitive empathy (MET and MASC) was largely unaffected by PSU. Additional linear regression analyses within PSU individuals revealed number of used substances as the best predictor for inferior performance in emotional empathy (p < .01), while severity of the use of single substances or substance-classes did not show a significant impact. These findings demonstrate cumulative adverse effects of stimulant PSU on an important facet of socio-cognitive functioning. Therefore, emotional empathy deficits should be targeted in future interventions and rehabilitations for individuals with PSU.