The symmetry rule: a seven-year study of symptoms and explanatory labels among Gulf War veterans

Abstract

Noticing medical symptoms can cause one to search for explanatory labels such as "ate bad food" or even "exposed to anthrax," and perhaps these labels may cause new symptom reports. The present study examined whether there is empirical support for this symptom-label "symmetry rule." We interviewed veterans (N= 362) from the Gulf War Registry in 1995 and 2002 about their medical symptoms and about their exposure to war-related hazards and stressors. Health symptom reports were strongly correlated between the two time periods and showed relatively stable mean levels, whereas recall of war-related exposures was notably unstable. Veterans starting with fewer medical symptoms recalled fewer war-related exposures seven years later. Initial recollection of chemical and biological warfare exposure (but not other exposures) longitudinally predicted novel medical symptoms. The findings generally support the symmetry rule hypotheses, although the evidence for the label to symptom link was less strong. The findings account for some variability in symptoms and exposure recall over time, but they do not, on their own, account for the Gulf War veterans' elevated number of unexplained medical symptoms.

Fig. 1

Structural model. The diagonal pathways test the symmetry rule. The hypothesis that symptoms give rise to explanatory labels was supported. The converse hypothesis, that explanatory labels give rise to symptoms, was partially supported. For the sake of visual clarity, the diagram shows only causal pathways whose coefficients are adjusted for control variables, but not the control variables, the correlations of variables within time periods, or the time-lagged correlations of observed variables’ error terms in the measurement models (see Table III). **p < 0.001, *p < 0.05.