29 CFR Part 1630, Regulations to Implement the Equal Employment Provisions of the ADA (Title I Regulations with amendments issued through May 2016)

(i) At all times taking into account the principles in paragraphs (j)(1)(i) through (ix) of this section, in determining whether an individual is substantially limited in a major life activity, it may be useful in appropriate cases to consider, as compared to most people in the general population, the condition under which the individual performs the major life activity; the manner in which the individual performs the major life activity; and/or the duration of time it takes the individual to perform the major life activity, or for which the individual can perform the major life activity.