The course begins by providing some fundamental background on addiction, its relatively recent rise in prevalence, and the scope of the problem today. It then turns to one of the most important discoveries in the science of addiction - namely, that all addictions hijack the brain's natural reward system, leading to an almost-irresistible urge to pursue the object of the addiction. The normal operation of the reward system, the way it is changed in addiction, and the crucial role of dopamine - the so-called addiction molecule - will all be covered in depth. The course will also explain the genetics of addiction and explore why some people are significantly more susceptible to addiction than others. The second major section of the course will focus on drugs ... These lectures will explain how these drugs work and how their chronic use can lead to dependence and addiction. The final section of the course will discuss so-called behavioral addictions, such as pathological gambling, food addiction, and video game addiction.