The reciprocal relationship between work characteristics and employee burnout and engagement: a longitudinal study of firefighters. 
The paradigm of this study is positive occupational psychology, with the job demands-resources model as the research model and the Conservation of Resources theory as the general stress theory.  The research design analyses the job demands-resources model's dynamic nature with normal and reversed causation effects between work characteristics and psychological well-being among Portuguese firefighters.  In addition, we analyse a positive (engagement) dimension and a negative (burnout) dimension in the firefighters' well-being, because previously, studies have merely focused on the strain or stress of these professionals.  The research questionnaire was distributed to a sample of 651 firefighters, and a two-wave full panel design was used.  Cross-lagged panel analyses indicated that the causal direction of the relationship between organizational demands and burnout is reciprocal.  Also, we found that the reciprocal model, including cross-lagged reciprocal relationships between organizational demands/supervisory support and burnout/engagement, respectively, is what fits the data best.  Practical implications to develop organizational change programmes and suggestions for future research regarding the promotion of occupational health are discussed.