Exploring Dual Diagnoses: Psychopathological Characteristics in the Co-Occurrence of Schizophrenia and Addiction: A scoping review

Background: The co-occurrence of schizophrenia and substance use disorders (SUDs), referred to as dual diagnosis, represents a significant challenge in psychiatric research and clinical practice. The interplay between these conditions complicates symptomatology, diagnosis, and treatment, necessitating an integrated approach to care. Summary: This scoping review systematically examines the available literature on the psychopathological characteristics of individuals with dual diagnosis, emphasizing symptomatologic clusters associated with different substances. A systematic search was conducted in Medline and Scopus databases to identify original research articles published in the last 20 years. Studies examining psychosis-related symptoms in individuals with SUDs were included, excluding non-original research, non-English articles, and studies not focusing on dual diagnosis. A total of 129 studies were included, with cannabis being the most frequently studied substance, followed by alcohol, stimulants, and opioids. The most commonly reported symptoms were positive symptoms (hallucinations, delusions, paranoia, disorganized thinking), cognitive impairments, and negative symptoms (social withdrawal, anhedonia). Emotional dysregulation, impulsivity, and aggression were also frequently documented. Substance-induced psychosis was found to differ from primary psychotic disorders in symptom severity, age of onset, and associated comorbidities. Key Messages: The psychopathology of dual diagnosis is multifaceted, with overlapping and complex symptom presentations. Substance use can exacerbate or trigger psychotic symptoms, making differential diagnosis challenging. These findings highlight the need for integrative treatment strategies that address both psychotic and substance-related symptoms. Further research is needed to develop standardized diagnostic criteria and targeted interventions for dual diagnosis patients.