OBJECTIVES: Negative symptoms of schizophrenia (NSS) are characterized by apathy, emotional inexpressibility and lack of social interest and impose significant economic burden on patient and society. Substance abuse (SA) is often associated with schizophrenia but there are relatively fewer and often inconclusive studies on impact of SA on NSS patients. The purpose of the study is to compare the utilization of healthcare resources and costs associated with SA as comorbidity with NSS patients versus NSS patients without SA.

METHODS: Cross-sectional study was conducted on the Decision Resources Group (DRG) Real World Evidence US claims and EHR datasets for the year 2016-2017. DSM-IV/ICD-9/ICD-10 codes were used to identify NSS patients (≥2 negative symptoms) and substance abuse as comorbidity. Descriptive analysis was conducted on two groups, NSS with SA and NSS without SA. Generalized linear models with log link were used to estimate outpatient visits, inpatient hospital stays, and gamma log link to estimate the cost of treatments adjusted for age, gender, payer-type, region, and other comorbidities.

RESULTS: The study included 8,282 NSS patients with 59% male and mean age 54 years. NSS patients with SA had significantly greater unadjusted mean number of outpatient visits (13.39 vs 6.56, p≤0.001) and longer inpatient stays (49.3 days vs 21.75 days, p≤0.001) compared to NSS patients without SA. After adjusting for covariates, patients with SA had 1.43 times higher expected outpatient visits (95%CI:1.31-1.57, p≤0.001), 2.23 times higher expected inpatient hospital stays (95%CI:1.75-2.83, p≤0.001), 2.04 times higher expected annual behavioral inpatient cost of care (95%CI:1.80-2.32, p≤0.001) and 2.38 times higher expected total cost of treatments (95%CI:2.19-2.59, p≤0.001) compared to NSS patients without SA.

CONCLUSIONS: This study demonstrates higher healthcare utilization and cost among comorbid NSS patients compared to NSS patients without SA and shows need for public health attention to alleviate substance abuse among NSS patients.