Perceived stress and delay discounting in schizophrenia, cannabis use disorder, and co-occurring disorders

Steeper delay discounting (DD) reflects greater impulsivity and has been reported in individuals with schizophrenia (SCZ) and those with substance use disorder, who also tend to report high psychological stress. We sought to compare DD in people with SCZ, cannabis use disorder (CUD), and comorbid SCZ-CUD, and determine its relationship to psychological stress in these groups, to inform treatment improvements. Participants were healthy controls (HC; n = 31) and individuals with DSM-IV diagnoses of SCZ (n = 21), CUD (n = 61), and comorbid SCZ-CUD (n = 40). After one week or more of verified abstinence from substances, participants completed the Delay Discounting Questionnaire and the Perceived Stress Scale. DD and perceived stress were greater in all three clinical groups compared to HC, though the clinical groups did not differ. Analyses did not detect a consistent relationship between stress and DD in any group, though females showed greater DD with increased stress when all clinical groups were combined. Findings indicate that, overall, perceived stress cannot account for steeper DD in patients with SCZ, CUD, and SCZ-CUD; thus, interventions for stress would not be expected to impact DD.