[The third version of COPSOQ-Istas21. An updated international instrument for the workplace.].

Objective: The Copenhagen Psychosocial Questio-nnaire (COPSOQ) is one of the most widely used in research and psychosocial risk assessment in the workplace. The adaptation of the third international COPSOQ version to Spain is described and the evidence of its validity and reliability presented.

Methods: Most of the items were already part of the previous versions I and II. The translation of the new items was done by means of translation/reverse translation. The questionnaire was included in the , a cross-sectional study of a representative sample of the wage-earning population in Spain (N=1,807). Descriptive statistics, internal consistency, floor and ceiling effects and factor structure were analysed. Prevalence Ratios adjusted by age, sex and occupational class (aPR) to mental health, general health and job satisfaction were calculated. Finally, population reference values were calculated for all dimensions of the instrument.

Results: The questionnaire showed an excellent factorial structure. All scales, except one, showed α of Cronbach >0.70. Comparing the COPSOQ-Istas21 III scales with their international references, Cronbach's α were higher and the ceiling and floor effects were lower; i.e. Organisational Justice: α=0.85 vs 0.74, ceiling and floor 1.6 and 9.4 vs 3.3 and 12.8. The aPR between all the psychosocial dimensions and the Mental Health, General Health and Job Satisfaction were in the expected direction and showed an association gradient.

Conclusions: COPSOQ-Istas21 version III presents psychometric properties analogous or better than the original in English language, and good indicators of validity and reliability, to be used in research and psychosocial risk assessment at the workplace in Spain.