Socio-cognitive functioning in stimulant polysubstance users

•Investigated cumulative effects of polysubstance use on socio-cognitive function.•Objectively validated group classification defined by hair and urine toxicology.•Decreased emotional empathy associated with increased number of used substances.•Increased number of used substances was accompanied with fewer social contacts.•Deficits not associated with single substance-classes or severity of substance use. 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