ObjectiveThe object of this study was to evaluate the evidence linking attachment insecurity to illness. Attachment theory describes lifelong patterns of response to threat that are learned in the interaction between an infant and his or her primary caregiver. Despite its biopsychosocial domain, attachment theory has only recently been applied to psychosomatic medicine.MethodMEDLINE and PsychInfo databases were searched from 1966 to 2000 for English language papers with key words “attachment” and “object relations.” Papers and their cited references were reviewed if they were directly related to physical illness, symptoms, or physiology. A hypothetical causal model was developed.ResultsDirect and indirect evidence from survey studies supports an association between attachment insecurity and disease. Animal studies and human experiments suggest that attachment contributes to individual differences in physiological stress response. There is also less robust support for insecure attachment leading to symptom reporting and to more frequent health risk behaviors, especially substance use and treatment nonadherence. Evidence supports the prediction from attachment theory that the benefits of social support derive more from attachment relationships than nonattachment relationships.ConclusionsAlthough the available data are suggestive rather than conclusive, the data can be organized into a model that describe attachment insecurity leading to disease risk through three mechanisms. These are increased susceptibility to stress, increased use of external regulators of affect, and altered help-seeking behavior. This model warrants further prospective investigation.