This Article  • Full text  • PDF  • Reply to article  • Send to a friend  • Save in My Folder  • Save to citation manager  • Permissions  Citing Articles  • Citation map  • Citing articles on HighWire  • Citing articles on ISI (10)  • Contact me when this article is cited  Related Content  • Similar articles in this journal  Topic Collections  • Psychiatry, Other  • Alert me on articles by topic

Helena Chmura Kraemer, PhD; Kimberly A. Wilson, PhD; Chris Hayward, MD, MPH

Arch Gen Psychiatry. 2006;63:604-608.

Context  Comorbidity is the rule rather than the exception with psychiatric disorders and is consequently of great interest to both researchers and clinicians. However, many studies of psychiatric comorbidity have been based on lifetime prevalence with mixed-age samples, a practice that (1) biases the assessment of epidemiologic comorbidity and (2) creates the appearance of comorbidity even when disorders are randomly associated. This bias is what we refer to as pseudocomorbidity.

Objectives  To clarify the source of the problem and to discuss strategies that might be adopted to deal hereafter with lifetime prevalence data.

Methods  A simulated example is presented to show that even when there is only random association between disorders, there will appear to be nonrandom comorbidity when lifetime prevalence is used with mixed-age samples. An actual example relating psychosis to phobia is presented to show the bias that can result and to illustrate one way of dealing with lifetime prevalence data.

Conclusions  Use of lifetime prevalence with mixed-age samples, used almost exclusively in psychiatric research, generates problematic results, especially when used for assessment of comorbidity, and should be viewed with some skepticism. Hereafter, we recommend that any future use of lifetime prevalence should require determination of the age of onset, even if only by retrospective report. Comorbidity then should be reported by age.

Author Affiliation: Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, Calif.

THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES

Comorbid Forms of Psychopathology: Key Patterns and Future Research Directions
Cerda et al.
Epidemiol Rev 2008;30:155-177.
ABSTRACT | FULL TEXT  

Prevalence, Correlates, Disability, and Comorbidity of DSM-IV Alcohol Abuse and Dependence in the United States: Results From the National Epidemiologic Survey on Alcohol and Related Conditions
Hasin et al.
Arch Gen Psychiatry 2007;64:830-842.
ABSTRACT | FULL TEXT  

Lifetime and 12-Month Prevalence of Bipolar Spectrum Disorder in the National Comorbidity Survey Replication
Merikangas et al.
Arch Gen Psychiatry 2007;64:543-552.
ABSTRACT | FULL TEXT