The second set of results presented in this review (129 articles) examined various biopsychosocial factors that may contribute to differences in pain sensitivity between healthy women and men.
The results revealed that the involvement of hormonal and physiological factors is either inconsistent or absent.
Some studies suggest that temporal summation, allodynia, and secondary hyperalgesia may be more pronounced in women than in men.
The evidence to support less efficient endogenous pain inhibitory systems in women is mixed and does not necessarily apply to all pain modalities.
With regard to psychological factors, depression may not mediate sex differences in pain perception, while the role of anxiety is ambiguous.
Cognitive and social factors appear to partly explain some sex-related differences. Finally, past individual history may be influential in female pain responses. However, these conclusions must be treated with much circumspection for various methodological reasons. Furthermore, some factors/mechanisms remain understudied in the field.
There is also a need to assess and improve the ecological validity of findings from laboratory studies on healthy subjects, and perhaps a change of paradigm needs to be considered at this point in time to better understand the factors that influence the experience of women and men who suffer from acute or chronic pain.