Although attempts have been made to define comorbidity, including the seminal work of the 1970s, it is a term that is used with different meaning across the scientific literature.1,3 Moreover, beyond comorbidity, multimorbidity is used to discuss the presence of several medical conditions in an individual, usually without reference to an index condition.2
References:
1. Krueger RF, Markon KE. Reinterpreting comorbidity: a model-based approach to understanding and classifying psychopathology. Annu Rev Clin Psychol 2006; 2: 111–133.
2. Valderas JM, Starfield B, Sibbald B, et al. Defining comorbidity: implications for understanding health and health services. Ann Fam Med 2009; 7 (4): 357–363.
3. Feinstein AR. The pre-therapeutic classification of co-morbidity in chronic disease. J Chronic Dis 1970; 23 (7): 455–468.