See also Tosetto A. Association or causation: the Janus face of observational research. This issue, pp 555-7.Summary. Background: The link between psychosocial factors and coronary heart disease is well established, but although effects on coagulation and fibrinolysis variables may be implicated, no population-based study has sought to determine whether venous thromboembolism is similarly related to psychosocial factors. Objective: To determine whether venous thromboembolism (deep vein thrombosis or pulmonary embolism) is related to psychosocial factors. Patients/methods: A stress questionnaire was filled in by 6958 men at baseline from 1970 to 1973, participants in a cardiovascular intervention trial. Their occupation was used to determine socio-economic status. Results: After a maximum follow-up of 28.8 years, 358 cases of deep vein thrombosis and/or pulmonary embolism were identified through the Swedish hospital discharge and cause-specific death registries. In comparison with men who, at baseline, had no or moderate stress, men with persistent stress had increased risk of pulmonary embolism [hazard ratio (HR)=1.80, 95% CI: 1.21-2.67]. After multivariable adjustment, the HR decreased slightly to 1.66 (95% CI: 1.12-2.48). When compared with manual workers, men with white-collar jobs at intermediate or high level and professionals showed an inverse relationship between occupational class and pulmonary embolism (multiple-adjusted HR=0.57, 95% CI: 0.39-0.83). Deep vein thrombosis was not significantly related to either stress or occupational class. Conclusion: Both persistent stress and low occupational class were independently related to future pulmonary embolism. The mechanisms are unknown, but effects on coagulation and fibrinolytic factors are likely.