Diagnosis of mental illness has become increasingly reified. People are being labeled; they are seen as being mentally ill instead of having a mental illness. Unfortunately, negative stereotypes are associated with mental illness. According to labeling theory, the stigma of being labeled mentally ill actually causes one to be mentally ill as a result of effects described as self-fulfilling prophecy. According to a modified version of the theory, assumptions about causation are omitted, and only the negative impact on self-concept is addressed. This impact is described in later research about stigma and self-stigma. Stigma can have negative consequences for selfconcept by lowering self-efficacy, which fosters dysfunctional coping styles and ultimately reduces quality of self-concept. Also, stigma can be internalized and create self-stigma, in which the label predominates selfconcept and reduces self-esteem. Thus, eventually, the reification of diagnosis leads to lowered self-concept through stigmatization effects. In spite of these negative effects, it is reasonable to believe that positive effects also exist. A label could foster self-acceptance, causing one to seek treatment, and can also foster interpersonal understanding. It is argued that these effects should be investigated. On the basis of outcomes, it should bedecided whether diagnosis should or should not be reported to the patient.