This review is a comprehensive overview of the effects of various drugs, diseases, and disorders on attentional breadth in individuals. Here we discuss how chemicals such as Testosterone, progesterone, cocaine, Caffeine, alcohol, and ecstasy can affect attentional scope. As well as we explore the impact of several diseases and disorders, including Schizophrenia, ADHD, autism, rumination, and Huntington's disease, on attention shifting between global and local targets. Meanwhile, we provide an in-depth discussion of local and global processing, attentional processes, and their interconnections. Identifying the factors that affect attentional breadth can help researchers and clinicians develop effective interventions to improve cognitive abilities and enhance human performance.