Psychiatric comorbidity: fact or artifact?

Hanna M Van Loo,Jan-Willem Romeijn

doi:10.1007/s11017-015-9321-0

Abstract

The frequent occurrence of comorbidity has brought about an extensive theoretical debate in psychiatry. Why are the rates of psychiatric comorbidity so high and what are their implications for the ontological and epistemological status of comorbid psychiatric diseases? Current explanations focus either on classification choices or on causal ties between disorders. Based on empirical and philosophical arguments, we propose a conventionalist interpretation of psychiatric comorbidity instead. We argue that a conventionalist approach fits well with research and clinical practice and resolves two problems for psychiatric diseases: experimenter’s regress and arbitrariness.

Highlights

This article investigates the nature of comorbidity among psychiatric diseases, and considers how this reflects on psychiatric disease classification
Comorbidity is the result of classification choices and population characteristics To get a grip on psychiatric comorbidity, two elements are important: (1) how diseases are defined in terms of symptoms and (2) how frequently combinations of symptoms occur in a population
We have illustrated that rates of comorbidity depend on the interplay between disease definitions and symptom distributions in populations

Summary

Introduction

This article investigates the nature of comorbidity among psychiatric diseases, and considers how this reflects on psychiatric disease classification. One can interpret comorbidity in two different ways: either the comorbidity rates are determined by classification choices in the DSM and are artificially high, or they result from causal relations between psychiatric disorders.. Comorbidity is the result of classification choices and population characteristics To get a grip on psychiatric comorbidity, two elements are important: (1) how diseases are defined in terms of symptoms and (2) how frequently combinations of symptoms occur in a population.. We studied the presence of symptoms of anxiety (ANX, i.e., feeling anxious, nervous, or worried), depressed mood (DEP, i.e., feeling depressed, gloomy, or in the dumps), insomnia (INS), and concentration difficulties (CONC) for the majority of a period of at least 2 weeks (or at least 4 weeks in case of anxiety) during the subject’s lifetime These symptoms are part of MDD and GAD, which are diseases co-occurring very frequently [29]. In this case, comorbidity did not increase with a change of diagnosis; the proportion of patients suffering from comorbidity even decreased

Conclusions of the analyses

Findings

Conclusion