Evaluating and establishing national norms for mental wellbeing using the short Warwick–Edinburgh Mental Well-being Scale (SWEMWBS): findings from the Health Survey for England

PURPOSE: The Warwick–Edinburgh Mental Well-being Scale (WEMWBS), 14 positively worded statements, is a validated instrument to measure mental wellbeing on a population level. Less is known about the population distribution of the shorter seven-item version (SWEMWBS) or its performance as an instrument to measure wellbeing. METHODS: Using the Health Survey for England 2010–2013 (n = 27,169 adults aged 16+, nationally representative of the population), age- and sex-specific norms were estimated using means and percentiles. Criterion validity was examined using: (1) Spearman correlations (ρ) for SWEMWBS with General Health Questionnaire (GHQ-12), happiness index, EQ-VAS (2) a multinomial logit model with SWEMWBS (low, medium and high wellbeing) as the outcome and demographic, social and health behaviours as explanatory variables. Relative validity was examined by comparing SWEMWBS with WEMWBS using: (1) Spearman correlations (continuous data), and (2) the weighted kappa statistic (categorical), within population subgroups. RESULTS: Mean (median) SWEMWBS was 23.7 (23.2) for men and 23.2 (23.2) for women (p = 0.100). Spearman correlations were moderately sized for the happiness index (ρ = 0.53, P < 0.001), GHQ-12 (ρ = −0.52, p < 0.001) and EQ-VAS (ρ = 0.40, p < 0.001). Participants consuming <1 portion of fruit and vegetables a day versus ≥5 (odds ratio = 1.43 95% Confidence Interval = (1.22–1.66)) and current smokers versus non-smokers (1.28 (1.15–1.41)) were more likely to have low vs medium wellbeing. Participants who binge drank versus non-drinkers were less likely to have high versus medium wellbeing (0.81 (0.71–0.92)). Spearman correlations between SWEMWBS and WEMWBS were above 0.95; weighted kappa statistics showed almost perfect agreement (0.79–0.85). CONCLUSION: SWEMWBS distinguishes mental wellbeing between subgroups, similarly to WEMWBS, but is less sensitive to gender differences. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s11136-016-1454-8) contains supplementary material, which is available to authorized users.