What is the test for a disability under the Social Security Act?

The Social Security Act defines a disability as the "inability to engage in any substantial gainful activity by reason of any medically determinable physical or mental impairment which ... has lasted or can be expected to last for a continuous period of not less than 12 months." 42 U.S.C. 423(d)(1)(A). Such an impairment must result from anatomical abnormalities that are demonstrable by medically acceptable clinical or laboratory diagnostic techniques. 42 U.S.C. 423(d)(3)(1988); Cotton v. Bowen, 799 F.2d 1403, 1405 (9th Cir.1986). Moreover, the impairment must be "of such severity that [the claimant] is not only unable to do [her] previous work but cannot ... engage in any other kind of substantial gainful work which exists in the national economy...." 42 U.S.C. 423(d)(2)(A)(Supp. III 1991).