Petersen SM, et al. - Using a longitudinal study design, researchers conducted a prospective cohort study to explore the risk of substance abuse diagnosis in correlation to schizophrenia diagnosis. They identified a cohort of 3,133,968 people using various Danish registers. In total, 14,007 people developed schizophrenia, with 2,885 subsequently given a diagnosis of substance abuse during follow-up (103,212,328 person-years at risk). In Denmark, schizophrenia diagnosis was associated with increased risk of subsequent substance abuse diagnosis. In addition, adjustment for co-abuse significantly affected associations, making schizophrenia primarily associated with an increased risk of cannabis, alcohol, stimulants and other substances being abused. The correlation remained relevant 10–15 years after a schizophrenia diagnosis.