Sweden and the other Nordic countries have held an alternative way to many other countries of understanding and responding to substance use and addiction. The non-medical approach grew particularly strong in the 1960s, but this social perspective has, since the 1990s, become increasingly challenged. This chapter outlines the social understanding and the developments within substance use treatment (SUT), policy, and everyday society in Sweden. A renewed medicalization began at the turn of the millennium, and has accelerated in more recent years, increasingly so due to an underlying brain disease model of addiction (BDMA) and sometimes also by outspoken BDMA arguments. Some explanations for the BDMA’s entry into the Nordic non-medical stronghold are: the medical perspective embedded in both evidence-based practices (EBP) and New Public Management (NPM), and the related fragmentation of the treatment system and demands for cost-effectiveness, communication and public outreach. Explanations are also found in worldwide trends, e.g., a mainstreaming of diagnoses; the public health movement; drug-related deaths and a push towards medical harm reduction measures; and, most recently, by a BDMA rhetoric emerging in public and policy debate and SUT. Understood from processes of ‘copresence’ and ‘vaguification’, the BDMA is in line with these forces driving towards a biomedical understanding of substance use problems.