A 12-month prospective follow-up study of patients with schizophrenia-spectrum disorders and substance abuse: Changes in psychiatric symptoms and substance use
Introduction
Dual diagnosis (DD) patients are known to present more difficulties from a clinical management perspective than single diagnosis (SD) patients. Substance use has been found to exacerbate the positive symptoms of schizophrenia (Drake et al., 1989, Margolese et al., 2004, Negrete et al., 1986, Pulver et al., 1989) and to increase aggression, violence (Angermeyer, 2000, Soyka, 2000), as well as medication noncompliance (Bhanji et al., 2004, Coldham et al., 2002, Kamali et al., 2001, Margolese et al., 2004, Olfson et al., 2000, Swartz et al., 1998) in the chronic mentally ill. Furthermore, time to readmission or community survival is significantly reduced among DD compared to SD subjects, even when controlling for non-compliance (Hunt et al., 2002).
Some follow-up studies have found that only a small percentage of patients with severe mental illness (SMI) achieve stable substance use remission over time (Drake et al., 1996). The prevalence of active substance use disorders changed little during a 7-year naturalistic follow-up (Bartels et al., 1995) of a SMI sample, suggesting that remission and new cases were approximately equal. Another study, which found high remission rates among dually diagnosed patients, reported significantly higher dropout rates among patients with schizophrenia and other psychoses compared to patients with other diagnoses (Dixon et al., 1998).
In a retrospective 18-month study of 100 schizophrenic outpatients, between 30% and 40% were found to be using substances during each 3-month interval (Chouljian et al., 1995). Analysis of 59 of the subjects with complete data demonstrated that cocaine and multiple substances increased, while problem use of alcohol, marijuana and other drugs remained stable (Chouljian et al., 1995).
Caspari (1999) examined the impact of cannabis abuse on schizophrenia in a sample of 27 DD patients compared to 26 SD controls. He found higher rehospitalization rates and worse psychosocial functioning in the cannabis abuse group at follow-up after 68.7 ± 28.3 months. Of note, 48% of the DD patients had ceased all substance abuse, while only 1 SD patient started excessive alcohol use, and none showed significant drug use. The cannabis group also had additional thought disturbance measured on the Brief Psychiatric Rating Scale (BPRS) and hostility measured on the Arbeitsgememeinscaft fur Methodik und Dokumetation in der Psychiatrie (AMDP) (German scale for measurement of psychotic symptoms) compared to the control group at the follow-up assessment (Caspari, 1999). The study design produced group comparisons for psychiatric symptoms that were cross-sectional, rather than within-subjects as the BPRS and AMPD were conducted only at follow-up and not at baseline.
It seems possible that increased symptoms expressed by DD patients in some studies are accounted for by medication non-compliance as well as the direct effect of substances of abuse on the production of psychiatric symptomatology. Buhler et al. (2002) followed 29 DD and 29 SD first episode patients for 5 years. Among the patients available for follow-up assessments, those with a DD had more positive symptoms and less affective flattening (Buhler et al., 2002). Once again, changes in drug use prevalence or severity during the follow-up period were not explored.
The impact of 12 months of treatment in a general hospital outpatient psychiatry service for patients with severe and persistent mental illness including schizophrenia, schizoaffective disorder and related psychoses was explored in the present study. Changes in the expression of psychiatric symptoms and use of substances of abuse were prospectively evaluated to ascertain if continuing substance abuse and dependence were associated with poorer therapeutic response.
Section snippets
Sample selection
The sample consisted of all patients with schizophrenia-spectrum disorders (schizophrenia, schizoaffective disorder, delusional disorder, psychosis NOS), who were referred to the Continuing Care Service (CCS) of the McGill University Health Centre—Montreal General Hospital (MGH) site. The MGH is a tertiary care hospital serving a diverse urban population and the CCS cares for all those patients with severe and persistent mental illness (Margolese et al., 2004). There are no specific selection
Results
The patients in this cohort were chronically ill with approximately 16 years since first diagnosis. Subjects with a DD were more likely than SD to be male, non-compliant with medications at intake and younger when they first received psychiatric treatment (Table 1). There were no significant differences between SD and DD patients on any other demographic variable. Medication compliance rates differed markedly at baseline, but were similar among the 3 groups at follow-up, with a higher
Discussion
The present study demonstrates that when DD patients are adequately treated for their psychiatric illness there is considerable amelioration in their psychotic symptoms. Moreover, the reduction in psychosis does not appear to be related to the type of antipsychotic prescribed (typical vs. atypical). The 12-month follow-up rate of 71% was considered to be reasonable for a chronic psychosis population in an ambulatory care setting. While the numbers did not reach statistical significance, there
Acknowledgements
The authors would like to thank Drs. Allan Fielding, Richard Montoro and Warren Steiner for their assistance in patient recruitment. This research was supported by a grant awarded to K.G. from the National Health Research and Development Program (Canada).
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