20 C.F.R. § 404.1521
If you are not doing substantial gainful activity, we will then determine whether you have a medically determinable physical or mental impairment(s) (see § 404.1520(a)(4)(ii) ). Your impairment(s) must result from anatomical, physiological, or psychological abnormalities that can be shown by medically acceptable clinical and laboratory diagnostic techniques. Therefore, a physical or mental impairment must be established by objective medical evidence from an acceptable medical source. We will not use your statement of symptoms, a diagnosis, or a medical opinion to establish the existence of an impairment(s). After we establish that you have a medically determinable impairment(s), then we determine whether your impairment(s) is severe.
20 C.F.R. §404.1521