Illicit drug use severity linked to outcomes in schizophrenia patients
MedWire News: Schizophrenia patients who are moderate or severe users of illicit substances have significantly poorer outcomes than those who are either mild users or abstainers in terms of psychosis symptoms, depression, and quality of life (QoL), research shows.
"Substance use disorders have been found to be substantially more prevalent among those diagnosed with schizophrenia than in the general population," explain Karin Kerfoot (Yale University School of Medicine, New Haven, Connecticut, USA) and team.
They add that although previous studies have suggested that comorbid substance abuse is associated with poorer outcomes in patients with schizophrenia, and that such findings are widely accepted, most of these studies were published before 2000, many rely on small, local samples, and have often focused on specific subpopulations, such as the severely ill.
To investigate further, the team assessed data on 1432 patients with schizophrenia who participated in the National Institute of Mental Health-funded Clinical Antipsychotic Trials of Intervention Effectiveness (CATIE) study. The study is the largest to date examining the effectiveness of several antipsychotic medications in schizophrenia patients in "real-world" settings.
All of the participants were followed-up for 18 months and outcomes were compared among moderate or severe drug users (n=162), mild users (n=481), and non-users (abstainers; n=789).
Moderate or severe illicit substance use was determined by evidence of drug use from study assessments (urine drug screening, self-report, family report, etc.), and scores greater than 2 on the clinician-rated Alcohol or Drug Use Scale (ADUS). Mild use was defined by a positive result on any of the drug use indicators, with ADUS scores of 2 or less, while abstainers were identified as those without any evidence of drug use.
After accounting for baseline variables, the researchers found that moderate or severe drug users had significantly poorer outcomes at 18 months compared with mild users and abstainers.
Specifically, compared with mild users and abstainers, moderate or severe drug users had poorer total scores on the Positive and Negative Syndrome Scale, at 67.26 and 67.98 versus 71.50, and the Calgary Depression Scale, at 1.44 and 1.43 versus 1.51.
Moderate or severe drug users also had poorer QoL at 18 months compared with mild users and abstainers, with respective scores of 2.53 versus 2.71 and 2.74 on the Heinrichs-Carpenter QoL Scale, 4.42 versus 4.60 and 4.58 on the Lehman self-report item, and 64.54 versus 67.30 and 67.47 on the visual analog assessment.
However, there were no significant differences among the groups at 18 months regarding neurocognitive functioning or employment.
Kerfoot and colleagues conclude in the journal Schizophrenia Research: "This study thus extends previous work, indicating that it was not merely the use of illicit substances that predicted poor outcomes but rather, the severity of drug use which was the clinically meaningful variable."
They add that the findings highlight "the importance of comprehensive assessment and treatment of illicit substance abuse in schizophrenia. Long-term treatment approaches that integrate harm reduction strategies may offer promise in maximizing positive outcomes for such dually diagnosed patients."
By Mark Cowen