Abstract
The current study consists of a systematic review of the quantitative literature on siblings of individuals with mental illness (MI). Despite the prevalence of mental illness, little is known about how siblings are specifically affected in areas of psychosocial, emotional, and behavioral outcomes. The review yielded 56 studies that examined outcomes such as behavior problems, the sibling relationship, caregiving experiences, and knowledge of mental illness among siblings. The majority of studies from the initial search were focused on siblings-as-comparison group, examining siblings for risk factors for developing mental illness. In total, the study samples covered a sibling age range of 6–81 and a patient age range of 4–84. About half (k = 27) of the included studies had samples primarily composed of siblings of individuals with schizophrenia, leaving other MI diagnoses such as depression, anxiety, and mood disorders underrepresented. However, results from comparison studies were mixed—half found that the MI-Sibs had fewer negative outcomes than the comparison group, and half found that MI-Sibs had more negative outcomes. Multiple factors, including female sibling gender, greater severity of MI symptoms, and belief in the patient’s ability to control their own behavior, were all related to more negative outcomes for MI-Sibs. Future work will focus on expanding the representativeness of MI-Sibs samples and analyzing experiences of both the sibling and the individual with MI.