The brain regions and neuronal processes that underlie addiction extensively overlap with those needed for cognitive functions, including learning, memory, and reasoning. Addiction worsens cognitive functions, making it more challenging to maintain abstinence and potentially leading to progression into neurodegenerative disorders. Furthermore, individuals living with neurodegenerative disorders can engage in behaviors, such as self-medication, due to impaired judgment and impulsivity associated with their condition. Addressing either of these conditions becomes markedly more intricate when they co-occur. This book explores the intricate and often overlooked connection between neurodegenerative disorders and addiction. It delves into the complex interplay between the two areas, discussing preclinical to clinical findings that highlight commonalities, shared risk factors, interplay and causality, comorbidity, management, and evidence-based interventions. By examining all these factors, an international team of contributors offer a comprehensive understanding of this underexplored intersection and its profound implications on affected individuals and their families, the healthcare system, and treatment strategies.