Autism Spectrum Disorder (ASD) is a lifelong neurodevelopmental disorder that is becoming increasingly common. Autism does not yet have a known etiology, nor a definitive diagnostic test, thus making diagnosis a difficult and rarely uniform task. Currently, ASD is behaviorally diagnosed based on criteria defined by the American Psychiatric Association in the Diagnostic and Statistical Manual of Mental Disorders (DSM). Recently, a change was made in the criteria from more lenient criteria in DSM-IV-TR, to more narrow criteria laid out by the DSM-V, which supersedes the DSM-IV-TR. This drastic change raised many questions and debates about which set of criteria are better. The more lenient criteria offers a more inclusive diagnosis giving greater access to therapies; while the narrow diagnostic criteria excludes some individuals, creating a more uniform diagnosis that's easier to use in research. This thesis analyzes the change in diagnostic criteria from the DSM-IV-TR to the DSM-V and the effects of these changes on the practices of diagnosis. In addition, it explores the implications of this change for the families of children with autism and for those involved in autism research, examining their respective opinions and interests pertaining to narrow verses broad diagnostic criteria. Building on this analysis, the thesis offers recommendations about diagnostic criteria should be set. It argues that the wellbeing of patients takes priority over the interests of researchers, and thus diagnosis should be done in a way that offers the best prognosis for all children who suffer from autistic symptoms.