Nonsuicidal Self-Injury and Co-Occurrence

Abstract

Comorbidity is the co-existence of two or more distinct diseases or disorders in the same individual at the same time (Achenbach, 1991; Caron & Rutter, 1991). Research on this clinical phenomenon is extremely important to our field because of its implications for past, current, and future classification systems, etiological theories, treatment outcomes, treatment recommendations, and developmental course (Keiley, Lofthouse, Bates, Dodge, & Pettit, 2003). However, the term, like selfinjury, has repeatedly been used in inaccurate and inconsistent ways in research and clinical work. One central issue in this area relates to the fundamental distinction between what Caron and Rutter (1991) call “apparent comorbidity” and “true comorbidity.” The former refers to the coexistence of multiple conditions being produced artifactually by one or more confounds such as chance occurrence, referral and detection biases, nosological confusion, multiformity, developmental transience, and measurement variance (Caron & Rutter, 1991; Hinden, Compas, Howell, & Achenbach, 1997; Klein & Riso, 1993; Lilienfeld, Waldman,• • • •& Israel, 1994). In contrast, true comorbidity is reserved for cases where these artifacts have been empirically ruled-out as explanations for joint occurrence. Unfortunately, many researchers have not separated artifactual from true comorbidity but have instead accepted comorbidity as a factual rather than hypothetical entity.