Carolien Zeetsen

17 CHAPTER General introduction 1 General introduction Substance (ab)use has profound societal, psychological but also cognitive consequences, as many substances have a direct or indirect impact on the cognitive functioning of the brain. Characterizing these cognitive consequences is highly relevant for treatment of and care for individuals with a substance use disorder. According to the latest available numbers of the National Alcohol and Drug Information System in the Netherlands (Wisselink et al., 2016), just short of 65,000 unique individuals were treated in addiction health care in 2015, with a declining trend since 2011. The most common primary substances of abuse are alcohol (45%), cannabis (17%), opioids (14%) and cocaine (11%). In about 42% of cases multiple substances are (ab)used (Wisselink et al., 2016). While the above numbers provide a clear image of the magnitude of the problem ‘addiction’, they most likely only reflect the tip of the iceberg as the substance users that do not seek treatment have not been taken into account. Of the patients who seek treatment, the prevalence of cognitive impairment is unclear. In this introductory chapter of my thesis I will first discuss the concept of substance use disorder (SUD) and the terminology used in this field. I will then provide an overview of what kind of cognitive deficits may occur by briefly summarizing the evidence for the impact of different substances on cognitive functioning. Next, I will discuss the consequences that cognitive impairments have on treatment and its outcome. Subsequently, I will explain in more detail the challenges in the assessment of these impairments and the use of cognitive screeners. Finally, I will end this introduction with an outline of my thesis. Substance–related and addictive disorders In the Diagnostic and Statistical Manual of Mental Disorders (DSM–5; American Psychiatric Association, 2013), the term ‘addiction’ is no longer being used. Instead, the new class ‘Substance–related and Addictive Disorders’ is used, which is divided into SUD and substance–induced disorders. The latter includes intoxication, withdrawal and other mental disorders that are induced by the substance. The former, SUD, is described as: ‘a cluster of cognitive, behavioural, and physiological symptoms indicating that the individual continues using the substance despite significant substance–related problems.’ (APA, 2013, p. 483).