Volunteers and design
The ethics committee Oxfordshire REC B (Ref. 09/H0605/60) approved the study. All participants gave written consent. Fifty subjects (18 males; mean age =28.93±7.7 years) were recruited from the general population, based on neuroticism scores on the Eysenck Personality Questionnaire (EPQ) (Eysenck and Eysenck, 1975) either low (⩽6) or high (⩾16), approximately corresponding to the mean neuroticism scores of the same aged general population (Eysenck et al, 1985) +1 SD, which conveys an 50–60% increase in lifetime risk for developing depression (Kendler et al, 1993). Participants were screened for axis I disorders using the Structured Clinical Interview for DSM-IV (First et al, 1996) and completed the State-Trait Anxiety Inventory (Spielberger et al, 1983), Beck Depression Inventory (Beck et al, 1961), Dysfunctional Attitude Scale (Weissman and Beck, 1978), and visual analogue scales (VAS) rating happiness, sadness, hostility, alertness, anxiety, and calmness. Three subjects were excluded owing to history of depression (before data collection, all from the high neuroticism group) and three owing to bad quality of data recording (two from the high and one from the low neuroticism group). The final sample comprised 44 subjects (17 males, mean age=29.6±7.9 years), of which 24 had low neuroticism scores (Low Ns) (10 males, mean N=2.62±1.4) and 20 had high neuroticism scores (High Ns) (7 males, mean N=18.45±2.2). Gender imbalance in the High Ns group reflects the personality trait distribution in the general population (Lynn and Martin, 1997).