Personality and the modulation of effects of sleep loss on mood and cognition

Participants (n=31, males=15, females=16, mean age=21.4 years) deprived of sleep for 29-35 h showed significant deficits on logical reasoning and on bipolar Profile Of Mood States total mood. Deficits in mood due to sleep loss correlated significantly with neuroticism, extraversion and usual sleep duration, and there was a statistically significant quadratic function of mood change with locus of control (LOC) score, such that internals and extreme externals had a smaller mood deficit after sleep loss than did moderate externals. Internals had been hypothesised from previous work to be less affected by stresses, including sleep loss, and we suggest that extreme externals may have been more susceptible to the positive motivating effects of the research assistants and the sleep laboratory environment, including involvement in various sociable leisure activities. Regression analysis showed that the only significant personality predictors of change in total mood were neuroticism (β=-0.40) and the quadratic function of LOC (β=0.39). Change in logical reasoning performance was significantly correlated with change in total mood (r=0.36), but with none of the personality variables.