Comorbidity of mental disorders and alcohol‐ and drug‐use disorders: Analysis of New South Wales inpatient data

Abstract

Alcohol- and other drug-use disorders have been found to be associated with mental disorders, however, complete characteristics of these comorbid mental disorders are not completely clear in early population based studies. This study aimed to explore the extent and profiles of comorbid mental disorders with alcohol- and other drug-use disorders using a large inpatient dataset. The data source was the New South Wales (NSW) Inpatient Statistic Data Collection which collects the clinical data of hospital admissions in NSW, Australia. The data were coded using the International Classification of Diseases-10th Revision (ICD-10). The data were from 1 July 2005 to 30 June 2006 the Australian financial year and statistical analysis was performed using SAS. Of 1 592 156 patients admitted, 91 510 (6%) had at least one mental disorder diagnosis and 18 283 (1.1%) had at least one alcohol- or other drug-related diagnosis. Of these patients, an overall 9.6% had dual diagnoses. Comorbidity was nearly five times higher in alcohol- and other drug-use disorders than in mental health disorders (52.4% vs. 10.5%). Comorbidity was higher in males than females (12% vs. 7.1%) and was the most common in patients aged from 20 to 49 regardless of sex. There was a significantly increased risk of developing a comorbid condition in all age groups above 10 years. The most common mental health disorders were major depressive disorders, followed by dementia, anxiety and severe stress. Alcohol-use disorder was the most common diagnosis, followed by cannabis and opioids. This study shows the characteristics of comorbid mental and alcohol- or other drug-use disorders. The study extends our understanding of issues addressed in previous population studies.