***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: & NA ; Gender differences in pain habituation , temporal summation , and pressure hyperalgesia evoked by repeated injections of glutamate into the dominant trapezius muscle were investigated . The  glutamate‐evoked muscle pain intensity and pressure pain threshold ( PPT ) were assessed . The PPTs were measured bilaterally in the trapezius muscles ( local pain area ) and posterolateral neck muscles ( referred pain area ) after glutamate injection in healthy and age‐matched males and females ( each n=14 ) .  Two glutamate injections ( 0.4 ml , 2 M each ) were injected with an interval of 5 min . One injection of glutamate ( 0.4 ml , 2 M ) served as a control . Males , but not females , rated the second injection ( maximal pain intensity ) significantly less painful than the first injection . The area under the visual analogue scale pain curve of the second injection was significantly larger than the first injection in females . Repeated glutamate injections , but not one‐glutamate injection , significantly decreased PPTs in the local pain area , with no significant gender differences . No PPTs changes were observed either in the contralateral trapezius muscle or bilaterally in the referred pain areas in either sex . These results suggest that a less efficient pain habituation and a greater susceptibility to the development of temporal summation of muscle pain in females , but not in males , might be one of the contributing factors to the higher incidence of neck shoulder pain in females . In addition , the reduction of PPTs in the local pain area evoked by intramuscular glutamate injection may represent an early process of peripheral pressure hyperalgesia , which is most likely gender independent Abstract The aim of the current investigation was to compare the effects of two different attentional strategies ( focused vs. avoidance ) on how males and females respond to experimentally induced pain . One hundred healthy adults were instructed to either attend towards or away from cold pressor pain . Measures of pain tolerance , pain threshold and recovery were taken , as were self‐report measures of sensory and affective pain experiences . As expected , gender was found to moderate tolerance to pain : males were found to be more tolerant to cold pressor pain than females . With respect to the self‐report measures , males reported less sensory pain when they attended toward the pain than when they avoided it . However , a similar effect was not found in women , suggesting that attentional focusing may only be a useful strategy for males . These results are discussed in light of previous research & NA ; Aims of investigation : To quantify the magnitude of putative gender differences in experimental pressure pain threshold ( PPT ) , and to establish the relevance of repeated measurements to any such differences . Methods : Two separate studies were undertaken . A pressure algometer was used in both studies to assess PPT in the first dorsal interosseous muscle . Force was increased at a rate of 5 N /s . In study 1 , two measurements were taken from 240 healthy volunteers ( 120 males , 120 females ; mean age 25 years ) giving a power for statistical analysis of & bgr;=0.80 at & agr;=0.01 . In study two , 30 subjects ( 15 males , 15 females mean age 28 years ) were r and omly selected from study one . Fourteen repeated PPT measurements were recorded at seven , 10 min intervals . Mean PPT data for gender groups , from both studies , were analysed using analysis of covariance with repeated measures , and age as the covariate . Results : The mean PPT for each of the two measurements in study one showed a difference between gender of 12.2 N ( f=30.5 N , m=42.7 N ) and 12.8 N ( f=29.5 N , m=42.3 N ) , respectively , representing a difference of 28 % with females exhibiting a lower threshold . In study two , the mean difference calculated from 14 PPT repeated measurements over a 1 h period was comparable to that in study one at 12.3 N ( range 10.4–14.4 N ) again females exhibited the lower threshold . The differences in mean PPT values between gender were found to be significant in both study one , at ( P<0.0005 , F=37.8 , df=1 ) and study two ( P=0.01 , F=7.6 , df=1 ) . No significant differences were found in either study with repeated measurement ( P=0.892 and P=0.280 ) , or on the interaction of gender and repeated measurement after controlling for age ( P=0.36 and P=0.62 ) . Conclusion : Healthy females exhibited significantly lower mean PPTs in the first dorsal interosseous muscle than males , which was maintained for fourteen repeated measures within a 1 h period . This difference is likely to be above clinical ly relevant levels of change , and it has clear implication s for the use of different gender subjects in laboratory based experimental design s utilising PPT as an outcome measure UNLABELLED Two experiments assessed how interpersonal transactions influence responses to  cold pressor pain in women versus men . In Experiment 1 , 91 young adults ( 57 women , 34 men ) were r and omly assigned to either a no transaction ( NT ) condition in which they coped alone with the cold pressor test or a transaction opportunity ( TO ) condition in which they also had the option of interacting with an empathetic , reflecting experimenter . Compared to men , women had lower pain tolerance and reported more pain and catastrophizing , although there were no gender differences in support seeking or other ways of coping . Within the TO condition , women were no more likely than men to initiate a transaction , but female speakers were more pain-focused than male speakers , and speaking with the empathetic interaction partner had generally negative effects on pain perception and coping . In Experiment 2 , 126 young adults ( 76 women , 50 men ) were r and omly assigned to NT , TO , or experimenter-directed ( 1 ) Distraction ( DT ) , ( 2 ) Reinterpretation ( RT ) , or ( 3 ) Encouragement ( ET ) conditions . Although men had similar levels of pain tolerance across the 5 transaction conditions , women in NT and TO conditions exhibited reduced tolerance compared with those in the DT , RT , and ET conditions . Pain tolerance times among women in DT , RT , and ET conditions were equal to or exceeded those of men in these conditions . Together , findings suggest the nature of interpersonal transactions exerts a greater influence on women 's responses to noxious stimulation than those of men . PERSPECTIVE This study adds to literature indicating that women exhibit reduced tolerance for experimentally induced pain compared with men . These results suggest that the nature of interpersonal transactions also affects women 's responses to noxious stimulation , more than those of men It was investigated whether an angry state , induced by a  computer task with harassing comments , would lead to a decrease in cold pressor pain threshold and tolerance in comparison to a neutral situation . It was hypothesized that an increase in cardiovascular activity might partially mediate effects of anger . Furthermore , it was examined whether subjects given the opportunity to express anger would show reduced cardiovascular activity and pain report compared to subjects not given this opportunity . Finally , trait measures for anger expression style and hostility were included . The results show an increase instead of the expected decrease in pain tolerance for subjects in the harassment condition compared to those in the neutral condition . While cardiovascular reactivity was positively related to pain threshold and tolerance , increased anger was associated with increased pain report . It is suggested that anger and cardiovascular reactivity may have important but sometimes opposing influences on pain Objectives : Evidence has accumulated that men and women show different responses to noxious stimuli , with women exhibiting greater sensitivity to pain than men . Data concerning sex differences in Cortisol response patterns have revealed inconsistent results so far . The purpose of the present study was to examine sex differences in subjective pain and Cortisol response to a noxious stressor . Methods : Seventy‐six subjects ( 39 male and 37 female ) were investigated by a modification of the cold pressor test that consisted of intermittent immersion of the h and into ice water ( plunge test , PT ) . The PT was conducted twice , in consecutive trials , to guarantee a sufficient exposure to the noxious stressor for eliciting Cortisol responses . In each trial , tolerance time and pain ratings visual analog scale ( VAS ) were assessed . Seven saliva sample s ( c1‐c7 ) were collected to determine Cortisol levels at baseline ( c1‐c2 ) , directly before ( c3 ) and 20 minutes after noxious stress ( c4 ) , and during recovery period ( c5‐c7 ) . Results : We found no significant sex differences in tolerance time in trial 1 , but highly significant differences in tolerance time in trial 2 , with higher tolerance times in men . No significant sex differences were found for the VAS ratings of pain intensity and unpleasantness in the 2 trials . In contrast , a significantly larger Cortisol increase in men was observed compared with women . Analysis of covariance revealed that this result could not be attributed to sex differences in Cortisol level at baseline and in tolerance time . Discussion : The present study demonstrates that men show a larger Cortisol response to a noxious stressor than women that is not attributable to sex differences in subjective pain . The conclusion of a causal relation between larger Cortisol responses and higher pain tolerance thresholds in men is tempting but yet speculative & NA ; The purpose of the present study was to determine whether gender differences exist in the forebrain cerebral activation patterns of the brain during pain perception . Accordingly , positron emission tomography ( PET ) with intravenous injection of H2 15O was used to detect increases in regional cerebral blood flow ( rCBF ) in normal right‐h and ed male and female subjects as they discriminated differences in the intensity of innocuous and noxious heat stimuli applied to the left forearm . Each subject was instructed in magnitude estimation based on a scale for which 0 indicated ‘ no heat sensation ’ ; 7 , ‘ just barely painful ’ and 10 , ‘ just barely tolerable ’ . Thermal stimuli were 40 ° C or 50 ° C heat , applied with a thermode as repetitive 5‐s contacts to the volar forearm . Both male and female subjects rated the 40 ° C stimuli as warm but not painful and the 50 ° C stimuli as painful but females rated the 50 ° C stimuli as significantly more intense than did the males ( P=0.0052 ) . Both genders showed a bilateral activation of premotor cortex in addition to the activation of a number of contralateral structures , including the posterior insula , anterior cingulate cortex and the cerebellar vermis , during heat pain . However , females had significantly greater activation of the contralateral prefrontal cortex when compared to the males by direct image subtraction . Volume of interest comparison ( t‐statistic ) also suggested greater activation of the contralateral insula and thalamus in the females ( P<0.05 ) . These pain‐related differences in brain activation may be attributed to gender , perceived pain intensity , or to both factors The aim of this investigation was to evaluate whether the pressure pain threshold ( PPT ) in masticatory muscles of symptom-free subjects was influenced by fluctuations of the sex hormones . The  PPT  was measured with an electronic algometer for at least 10 consecutive menstrual cycles in 10 women using oral contraceptives and 10 women not using oral contraceptives , with a regular menstrual cycle ( 26 - 31 days ) . In addition , 10 men were measured in a regular pattern over a period of 1 year . All subjects were symptom-free with an age range between 18 and 39 years . Measurement sessions were held during three different cycle phases ( follicular , luteal , perimenstrual ) and each session consisted of four consecutive PPT measurements . By means of a linear mixed model ( SAS ) , the PPTs of the masster , temporalis and thumb muscles were compared between : ( 1 ) groups , ( 2 ) sex-hormonal phases , ( 3 ) the four consecutive measurements of each muscle per session and ( 4 ) time . The PPTs of the masseter ( p = 0.8419 ) and temporalis muscles ( p = 0.2786 ) did not change significantly over time . There was no significant difference in variance for the masseter ( p = 0.6250 ) , temporalis ( p = 0.9705 ) and thumb ( p = 0.7446 ) between the three groups . The PPTs of all muscles were significantly lower during the perimenstrual phases in the two female groups . The present data showed similar patterns of PPTs for the three muscle groups . Moreover , the results have shown a very good consistency of the PPTs over a long time period , both in males and females BACKGROUND Pain syndrome is thought to play a role in depression . This study assesses the prevalence of chronic ( > or= 6 months ' duration ) painful physical conditions ( CPPCs ) ( joint/articular , limb , or back pain , headaches , or gastrointestinal diseases ) and their relationship with major depressive disorder . METHODS We conducted a cross-sectional telephone survey of a r and om sample of 18 980 subjects from 15 to 100 years old representative of the general population s of the United Kingdom , Germany , Italy , Portugal , and Spain . Answers provided during telephone interviews using the Sleep-EVAL system  were the main outcome measure . Interviews included questions about mental disorders and medical conditions . Data on painful physical conditions were obtained through questions about medical treatment , consultations , and /or hospitalizations for medical conditions and a list of 42 diseases . RESULTS Of all subjects interviewed , 17.1 % reported having at least 1 CPPC ( 95 % confidence interval [ CI ] , 16.5%-17.6 % ) . At least 1 depressive symptom ( sadness , depression , hopelessness , loss of interest , or lack of pleasure ) was present in 16.5 % of subjects ( 95 % CI , 16.0%-17.1 % ) ; 27.6 % of these subjects had at least 1 CPPC . Major depressive disorder was diagnosed in 4.0 % of subjects ; 43.4 % of these subjects had at least 1 CPPC , which was 4 times more often than in subjects without major depressive disorder ( odds ratio [ 
    Output:
    
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 .