The inverted U model also has implications for sample selection to the extent that maternal distress is differentially present. Our own research findings showing increased maternal distress to be facilitative to both prenatal and postnatal development, for example, are based on samples composed predominantly of mentally healthy well-educated women who are most likely to participate as volunteers in longitudinal research. As such, they may not generalize to populations of disadvantaged women who face chronic socioeconomic stressors. Similarly, clinically depressed or anxious women may also experience prenatal distress beyond the mild-to-moderate range, and there is supportive evidence that the fetal response to the maternal Stroop stressor interacts with maternal psychiatric status.