Leonard Weller

Human menstrual synchrony: a critical assessment/.

This review on menstrual synchrony in human females has four purposes: (a) to determine whether or not the phenomenon exists, and whether it differs in the various groups studied: roommates in dormitories, roommates in private residences, close friends, work groups, mothers-daughters; (b) to assess the magnitude of its effect, i.e., to what extent does the single factor of living together affect menstrual synchrony?; (c) to examine the effects of menstrual-related factors, social interaction factors, and personality on menstrual synchrony; (d) to assess whether the findings support a pheromonal or common environmental explanation of menstrual synchrony. Several methodological issues are also discussed.

Menstrual synchrony between mothers and daughters and between roommates

Menstrual synchrony was examined in three groups of women: 1) mothers and their daughters; 2) women sharing a room in a private residence; and 3) women sharing a room in a dormitory. The intracouple difference in menstrual onset dates was the dependent measure. Mothers and daughters living in the same domicile displayed a significant degree of synchrony. Roommates in private residences were also synchronous, although not significantly more than roommates residing in dormitories.

MENSTRUAL SYNCHRONY IN FEMALE COUPLES

The menstrual cycles of cohabitating women have been found to synchronize, possibly through social and pheromonal mechanisms. The extent of this phenomenon, menstrual synchrony, was examined in 20 couples of lesbian women. Synchrony was very frequent, with half the subjects menstruating within 2 days of their partner. Factors related to the degree of synchrony included mutual activities, friendship and menstrual regularity.

Biological factors in mild mental retardation

A group of 434 children with non‐syndromic mental retardation was analysed for frequency of recorded prenatal, perinatal and infantile biological disturbances. Mildly retarded individuals of unrelated parentage, both idiopathic and familial, had a strikingly higher prevalence of recorded disturbances than did a control group of retarded individuals with consanguineous parents and of probably genetic aetiology. These disturbances were as frequent among those with mild retardation as among parallel groups with severe retardation. The most significant single disturbance among the midly retarded was a history of maternal reproductive inefficiency. These findings conflict with the view that mild retardation is predominantly ‘cultural‐familial’ and is not pathological in nature.

Pathogenic Factors in Idiopathic Mental Retardation

Pathogenic factors in à mentally retarded population were evaluated by comparing their frequency among three groups of patients: à control group with predominantly genetic retardation and consanguineous parents; à group with severe idiopathic retardation and unrelated parents; and à group with mild idiopathic retardation and unrelated parents. Seven factors were found to be significantly more common among the patients with idiopathic retardation than in the genetic control group: à history of maternal reproductive inefficiency; bleeding during pregnancy; toxemia during pregnancy; signs of perinatal stress; neonatal anoxia; neonatal jaundice; and seizures during the first year of life. à history of repeated maternal abortions was particularly associated with mild retardation, and infantile seizures were particularly associated with severe retardation. The latter association remained significant even after exclusion of all infantile spasms, neonatal seizures and symptomatic seizures.

Relative importance of genetic and nongenetic etiologies in idiopathic mental retardation: estimates based on analysis of medical histories

A method of analyzing subgroups of mental retardates for proportions of cases caused by nongenetic brain damage is presented here and applied to 490 Israeli retardates.

Menstrual synchrony: Only in roommates who are close friends?

This study examined menstrual synchrony among roommates residing in 20 university housing units. Menstrual synchrony was examined for roommates who were close friends and roommates who were not close friends, and by housing unit. The impact of personality, social-interaction and menstrual-related factors was also studied. To avoid limitations found in previous studies, (i) data were collected prospectively and (ii) over the entire academic year; (iii) high participation rate was obtained (86%); and (iv) women who used oral contraceptives were excluded. Menstrual synchrony was found among roommates who were close friends. Synchrony was not found for roommates who were not close friends, nor by housing units. The phenomenon of menstrual synchrony may more likely occur among close friends and women with intensive social contact than under the conditions common to university dormitories.

Menstrual synchrony under optimal conditions: Bedouin families.

Ovarian cycles of females living and interacting together have been shown to synchronize in a number of species. In humans, the related phenomenon of menstrual synchrony has been reported among roommates and best friends. Menstrual data were collected prospectively for 3 months from 27 Bedouin nuclear families living under conditions optimally conducive for synchrony: (a) women living together for many years, (b) a highly sexually segregated society, (c) standard living conditions, and (d) minimal use of oral contraceptives. Results show unequivocally the existence of menstrual synchrony: A 20%-25% shift toward synchrony was found for sisters-roommates, sisters-roommates who are close friends, and the family (all women in the family between 13 and 50 years of age).

Menstrual synchrony in a sample of working women

Menstrual synchrony has been typically studied among women who live together: dormitory roommates or family members sharing a bedroom or living in the same house. The current study examined menstrual synchrony in 51 pairs of women working together under conditions optimally conducive to synchrony. They had been together for at least 1 year, shared a relatively small office, worked there all day full time and contact with other people during the day was minimal. Prospective records of three menstrual dates showed a significant degree of synchrony for each of the 3 months. Menstrual onsets of close friends tended to occur on the average within 3.5-4.3 days of each other while onsets of co-workers who were not close friends were significantly more broadly ranged (7.7-9.0 days of each other). This is the first unequivocal demonstration of menstrual synchrony outside of the household.

Human menstrual synchrony in families and among close friends: examining the importance of mutual exposure.

Human menstrual synchrony was examined in a sample of 73 urban households with a relatively high degree of mutual contact and interaction but less than that of a previously studied, possibly unique sample of Bedouin families with an extremely high degree of contact, interaction, and sexual segregation (A. Weller & Weller, 1997). In addition, for the first time, menstrual synchrony was studied among best friends who did not live together and among sisters who did versus did not share a bedroom. A very high degree of synchrony was found among families (51%) and among sisters (51%), and a relatively high degree of synchrony was found among close friends (30%). The results suggest that synchrony can be attained without sleeping in the same bedroom or even in the same house. The findings also suggest that an effective range of mutual exposure is an attribute of human menstrual synchrony; below or above this range, the phenomenon may not occur.