Measuring symptoms of psychopathology and addiction severity with a single instrument: Development and psychometric properties of the Dual Disorder Rating Scale (DDRS)

Introduction: Currently, there is no psychometric tool that measures at the same time signs of psychopathological impairment and addiction symptoms in people with an addictive disorder. Instead, the co-presence of psychopathology in patients with addiction is frequent. Thus, it becomes important to assess both the aspects in order to do a valid diagnosis. To fill this gap, in this study, we developed the Dual Disorder Rating Scale (DDRS) to measure both psychiatric and addiction severity symptoms among individuals with addiction. Methods: We started from the 24-item Brief Psychiatric Rating Scale (BPRS), a hetero-evaluative multidimensional scale assessing the severity of psychiatric symptoms with Likert-type items ranging from 1 (not present) to 7 (extremely severe). To that scale, we added 10 items measuring signs of addiction (e.g., craving). Participants were 284 patients (80% males, mean age = 40.01, SD = 12.04) with a diagnosis of substance-addiction (cocaine, alcohol, cannabis, benzodiazepines) or nonsubstance related addiction (gambling) under treatment at specialized treatment centers across Italy. Fiftytwo percent of the sample had also a psychiatric diagnosis. Results: Item analysis showed a non-normal distribution of item responses. Thus, a logarithmic transformation was adopted. Exploratory factor analysis conducted with the 34 items suggested the necessity to delete four items. The resulting thirtyitems solution was found to have a four-factor structure. A randomized item parceling procedure confirmed the four factors, respectively defined as Mood Disturbance, Mania/Activation, Addiction, Reality Distortion. The four dimensions had a high internal consistency. The ability of the four dimensions to discriminate across addicted patients with and without a psychiatric diagnosis was investigated. Discussion: Findings indicate that the resulting DDRS, as a whole, may be used as a multifactorial hetero-evaluative instrument to assess both signs of psychopathological impairment and addiction symptoms in patients with addiction.