We performed a hierarchical clustering analysis on the inter-item rg’s of sample 1 to see whether the items could be grouped into genetically homogeneous clusters (Fig. 1). This analysis revealed two clusters (1: LONE/MIS/MOOD/FED-UP 2: NERV-FEEL/WORRY/TENSE/SUF-NERV), with mean rg = .84 (range: 0.77–0.91) within clusters, and a much lower mean rg = .59 (range: 0.38–0.77) between items from different clusters. The identified clusters coincide with the dimensions depressed affect and worry previously identified in factor analysis of the full EPQ-R neuroticism scale26.
