One percent of the working age population in the UK moves onto disability benefit each year, the highest in the OECD and twice the average, with 41% of claimants affected by mental disorder. The economic cost of mental ill-health in UK represents 4.5% of GDP. The UK has a high annual incidence of mental disorder at around 23% per year, among the highest in the OECD (OECD, 2014).
These statistics suggest that we don’t have a problem with failure to diagnose mental illness, but the process of diagnosis and treatment may be making substantially more people disabled than need to be. This may be related to the expectation that patients with minor affective symptoms must have medication and a sick note.
OECD 2014. Mental Health and Work: United Kingdom. Mental Health and Work. OECD Publishing.
A longitudinal cohort study with three years follow-up of 234 patients aged 55 and older with prevalent major depressive disorder found the median duration was 18.0 months (95% CI 12.8-23.1). 35% recovered within one year, 60% within two years and 68% within three years. A poor outcome was associated with severity of depression at baseline, a family history of depression and poorer physical functioning (Licht-Strunk et al., 2009).
This would indicate that applicants for ill health retirement with depression are generally (on balance of probabilities) expected to recover within two years unless there are additional prognostic factors.
LICHT-STRUNK, E., VAN MARWIJK, H. W., HOEKSTRA, T., TWISK, J. W., DE HAAN, M. & BEEKMAN, A. T. 2009. Outcome of depression in later life in primary care: longitudinal cohort study with three years' follow-up. Bmj, 338, a3079.