From the
Social Security Bulletin:
We use data from Social Security administrative records to examine the lifetime patterns of initial entitlement to retired-worker and Disability Insurance (DI) benefits across cohorts born in different years. Breaking out age-at-entitlement patterns for different birth-year cohorts reveals close adherence in entitlement ages to changes in program rules, such as increasing the full retirement age. The proportion of a cohort that becomes newly entitled to DI benefits rises noticeably during recessions and at ages 50 and 55, and cumulative entitlement rate patterns show that more recent cohorts rely increasingly on DI benefits in their late 30s and 40s.
If you look at the actual data, the correlation between recessions and disability claims seems to be weak to the point of being non-existent. Here's what the study says further on:
To further investigate the effect of the economy and the stance of the DI program regarding new entitlements, we next examine the incidence of new entitlements by year, 1969–2006, for the same cohorts studied above. Chart 8 shows the effect of the 1974–1975 recession, with a modest increase in entitlement rates across all cohorts. The 1980–1982 double-dip recession is notable in that no increase in new entitlements occurred: Those years correspond to restricted allowance rates. However, the 1984 Social Security Amendments relaxed some of the prior restrictions and extended allowances to people with certain mental and musculoskeletal impairments. That legislation not only changed labor market conditions, it likely contributed to increases in new entitlements in the 3–4 years leading up to the recession of 1990–1991. We also see rising entitlements in the years leading up to 2000–2001. The slow pace of the economic recovery following the 2001 recession corresponds with the continued high incidence of new DI entitlements in 2002–2006.
Basically, the report says that there is an association between recession sand disability claims except when there isn't and that increases in disability claims that come before a recession or after a recession are proof that recessions cause disability claims.
Overall, what I see here is proof that the number of people approved for Social Security disability benefits depends largely upon the policies followed by Social Security which should surprise no one.