Psychiatric Morbidity in Dependent Z-Drugs and Benzodiazepine Users

Zolpidem/zopiclone (Z-drugs) and benzodiazepines (BDZs) have different profiles of comorbidity, but studies have seldom explored these differences. This study examined psychiatric comorbidity in patients dependent on Z-drugs or BDZs attending substance abuse clinics in Hong Kong. In this retrospective chart review, the medical records of 207 patients (117 on Z-drugs and 90 on BDZs) treated between January 2008 and August 2012 were analysed. Demographic data, patterns of substance misuse and comorbid psychiatric diagnoses were recorded. Patients dependent on Z-drugs were younger (40.5 ± 10.4 vs. 46.8 ± 11.6; p < 0.001), had an earlier age of onset of drug misuse (p = 0.047) and were more likely to currently use cough syrup (29.5 ± 12.1 vs. 33.6 ± 14.5; p = 0.009) than the BDZs dependent patients. Overall, the Z-drugs and BDZs groups had a similar frequency of comorbid psychotic disorders, mood disorders and anxiety disorders. Mood disorders were the most common comorbid psychiatric disorders. The zopiclone group had a significantly higher percentage of psychotic disorders than the zolpidem group (25.5 % vs. 0; p = 0.022). To summarize, patients with Z-drugs or BDZs dependence have similar psychiatric comorbidities, with depressive disorder the most common comorbidity. Zopiclone is more likely to be associated with psychotic disorders than zolpidem.