Substance use disorders (SUDs) have dire consequences for the individual, family, and community. Although SUDs were once viewed as a moral issue, they are now understood to be complex, chronic brain illnesses associated with both genetic and non-genetic influences. The American Psychiatric Association recognizes SUDs associated with the use of 10 different substances, for example, alcohol, nicotine, opioids, cannabis, caffeine, hallucinogens, inhalants, sedatives, hypnotics, and stimulants. Environmental exposure to substances, early use, genetic influences, and neurobiology have all been correlated with an increased likelihood of the development of SUDs. Having a broader understanding of these complex disorders is key for prevention.