Can impairments that are episodic or in remission be considered disabilities?

Yes. The Americans with Disabilities Act Amendments Act of 2008 (ADAAA) specifically states that an impairment that is episodic or in remission meets the definition of "disability" if it would substantially limit a major life activity when active.

This means that a person with a chronic impairment with symptoms or effects that are episodic rather than present at all times can be considered as having disability even if the symptoms or effects only substantially limit a major life activity when the impairment is active. Thus, they are protected from discrimination under the ADAAA. Examples of impairments that may be episodic include, but are not limited to, epilepsy, hypertension, asthma, diabetes, major depressive disorder, bipolar disorder, and schizophrenia. An impairment such as cancer that is in remission but that may return in a substantially limiting form is also a disability under the ADAAA.