Neuropsychological aspects of dual diagnosis

Dual diagnosis (DD) has been described as the coexistence of a severe mental health condition and a drug abuse and/or dependence disorder. In the last decades, there has been a growing interest in the prevalence and characteristics of dual diagnosis, since it has been argued that DD patients show more clinical treatment difficulties and higher morbidity. Few works have studied the neuropsychological aspects of patients with DD, although neuropsychological deficits have been widely described both in patients showing a severe mental health condition and in those with a drug abuse and/or dependence disorder. Knowledge of the type and severity of potential neuropsychological deficits in patients with DD is of great relevance since it could be an interviewing factor for clinical treatment and prognosis. The present work aims to review the main data on attention, memory, and executive functions in dual diagnosis patients, from an explanatory point of view. We focus on the diagnoses of Schizophrenia and Bipolar Disorder since these have shown the highest prevalence and severity in DD and have provided a wealth of data. We describe the differences in neuropsychological performance found in these patients and the implications for clinical treatment and psychosocial functioning. Finally, we propose possible working ideas for future studies in order to improve our present knowledge of the neuropsychological aspects of DD.