Yet, little is known about the role neuroticism and life adversity play in the development of depressive symptoms.

A total of 184 subjects aged 20-80 years were examined in the cross-sectional study. The whole group consists of 4 subgroups, namely: inpatients with haematologic malignances, inpatients with various internal illnesses like the cardiovascular disease or diabetes, outpatients infected with HCV (before antiviral treatment), and healthy subjects. The Eysenck's neuroticism questionnaire (EPQ) and the Present State Examination (PSE from SCAN 2.0) were used in the study

Mean neuroticism scores in groups were similar (11.3, 12.6, 11.3, 10.0 respectively) differences were not statistically significant (ANOVA, F = 1.44, p = 0.23). Mean depression scores were different (6.33, 4.57, 3.93, 1.93 respectively), differences were statistically significant (ANOVA, F = 6.34, p < 0.001). Slopes of regression line between depression and neuroticism scores (0.73, 0.39, 0.5, 0.05 respectively) were not homogenous (F = 7.16, p < 0.001). Results revealed strong interaction between group variable and neuroticism in terms of their influence on depression mean scores (F = 22.9, p < 0.001). Residual effect of the group variable was weaker (F = 0.54, p = 0.21).

Differences in mean depression score among groups resulted mainly from symmetric interactions between group variable (adversity caused by an illness and treatment) and neuroticism. Slope of regression line between depression and neuroticism scores among subjects undergoing similar life adversity could be treated as a potential of this adversity to provoke emotional stress, and consequently depressive symptoms.