Subjective well-being is influenced by factors other than external events or physical
conditions. For the purposes of developing an instrument to measure health-related QOL,
personality effects could possibly be ignored and treated as a random variable. However
adaptation effects are a different issue: self-reported QOL may well differ from underlying
QOL (ie. represent underreporting). The apparently malleable and relative nature of QOL
self-assessments means self-reported QOL cannot be taken as a criterion measure for the
QOL of a given health state (in the sense of validity assessment). The fact that an
individual's report indicates acceptance of their state does not mean that they would not
greatly prefer an alternative one if the choice was available.