Reaction time and onset of psychological distress: The UK Health and Lifestyle Survey

Background: Cross-sectional studies have shown that depression is often accompanied by less efficient cognitive function, as indicated by slower speed of information processing. The direction of effect is unclear. We investigated prospectively whether slower processing speed, as indexed by longer simple or choice reaction time, is associated with an increased risk of psychological distress. Methods: Participants were 3088 men and women aged 18 and over who had taken part in the UK Health and Lifestyle Survey. Simple and choice reaction time was measured in the baseline survey. Symptoms of psychological distress were assessed at baseline and at the seven-year follow-up survey with the 30-item General Health Questionnaire. Results: In unadjusted models,a SD slower simple or choice reaction time at baseline was associated with odds ratios for psychological distress (≥5 on GHQ) at follow-up of 1.14 (1.06, 1.23) (p<0.001) or 1.13 (1.04, 1.22) (p=0.002) respectively. Further adjustment for age, sex, social class, educational attainment, health behaviours, number of chronic physical illnesses present, neuroticism and GHQ score at baseline had only slight attenuating effects on these associations. In fully adjusted models, a SD slower simple or choice reaction time at baseline was associated with odds ratios for psychological distress of 1.11 (1.02, 1.21) (p=0.017) or 1.11 (1.00, 1.24) (p=0.048), respectively. Conclusion: Slower processing speed may be a risk factor for the development of psychological distress. Future studies should explore the extent to which slower processing speed explains previously demonstrated associations between lower intelligence and poorer mental health.