A comparison of the performance of the 5-item mental health dimension of SF–36 (MHI–5) with that of the 12-item General Health Questionnaire (GHQ–12) in a defined, non-patient population, using standard statistical tests.
A postal survey of 3000 patients aged 16–64 years was conducted. Patients were randomly selected from the practice lists of two general practices chosen to represent populations with different socio-economic characteristics.
Considerable evidence was found for the internal consistency of both instruments (Cronbach's α 0.91 and 0.84 for GHQ–12 and the MHI–5 respectively) and for their construct validity in terms of distinguishing between groups with measured health differences. Both instruments showed a significant difference in the mean scores for men and women. In contrast to the GHQ–12, no correlation was found between age and score for the MHI–5. Both instruments were equally sensitive to socio-economic characteristics and to levels of social support The scores on the two instruments were highly correlated (Spearman rank correlation – 0.73).
The MHI–5 has comparable psychometric performance to the GHQ–12, and can be used to measure and compare mental health in defined populations. Operational advantages of the MHI–5 over the GHQ–12 are that it is in the public domain, is part of a general health measure (SF–36) and is shorter.