Examining the energy envelope and associated symptom patterns in chronic fatigue syndrome: does coping matter?

OBJECTIVE/Hypothesis The objective of this study was to examine sub-types of individuals with chronic fatigue syndrome based on variables that are associated with the energy envelope theory and to examine the role of coping strategies in explaining the differences found between the subtypes. METHODS Cluster analysis was used. Grouping variables included physical functioning, post-exertional malaise severity, and the extent to which an individual was outside of the energy envelope. These clusters were evaluated using discriminant function analysis to determine whether they could be differentiated based on coping styles. RESULTS Cluster analysis identified three groups. Clusters 1 and 2 were consistent with the energy envelope theory. However, Cluster 3 was characterized by patients with the most impairment, but they were to a lesser extent exceeding their energy envelope. Coping strategies explained a small percentage (10%) of the variance in differentiating the clusters. DISCUSSION Energy maintenance may be associated with improved functioning and less severe symptoms for some. However, patients in Cluster 3 were closer to remaining within their energy envelope and also used higher levels of adaptive coping but were more impaired than Cluster 2. This suggests that adaptive coping strategies were not associated with improved health, as members of Cluster 3 were severely limited in functioning.