Drug addiction or alcoholism (DAA) cannot be a basis for Social Security disability. In fact, if DAA is a contributing factor material to your disability, you are not entitled to disability benefits. See 42 U.S.C. 423(d)(2)(C).
Social Security has a regulation governing how it will determine whether or not DAA is material to a disability claim. For an SSI claim, the regulation is 20 C.F.R. 416.935. The key factor is whether Social Security would still find a claimant disabled if that claimant stopped using drugs or alcohol.
To do this, the SSA must evaluate which of the claimant's impairments would remain if the claimant stopped using drugs or alcohol. The SSA will then determine whether or not the claimant's remaining limitations would be disabling. If the remaining limitations would not be disabling, then DAA is a contributing factor material to disability, and the claim would be denied.
However, sometimes it is impossible to untangle the effects of DAA from other impairments, particularly mental impairments. If the judge cannot determine the effect DAA has on the claimant's impairments, then DAA is not material. A tie goes to the claimant, pursuant to emergency message 96200 (see question #29).