Genetic and environmental factors in primary dysmenorrhea and its relationship to anxiety, depression, and neuroticism

A multidimensional appraisal of early menstrual pain experience

BACKGROUND

Symptomatic dysmenorrhea is a global problem, affecting more than 40% of menstruating persons. Cross-sectional studies have implicated psychosocial, biological, and sensory factors in dysmenorrhea but the mechanisms are not fully understood. Only a few prospective longitudinal studies have evaluated such factors in relation to the emergence and course of dysmenorrhea at menarche.

OBJECTIVE

This study aimed to describe the initial menstruation experience and to evaluate the association of premenarchal psychosocial and sensory factors with the intensity of dysmenorrhea during the period in the fourth month.

STUDY DESIGN

This was a prospective cohort study of adolescents who completed premenarchal assessments and postmenarchal daily menstrual diaries for their first (n=149) and fourth month periods (n=114). They were recruited shortly before menarche and completed baseline assessments, including psychosocial questionnaires and experimental pain sensitivity (pressure testing, bladder provocation), and their parents completed related pain questionnaires. The relation between the hypothesized premenarchal factors and month 4 dysmenorrhea intensity was evaluated using Kruskal-Wallis and chi-square tests for low (<3 on a 0-10 scale) vs higher (≥3) menstrual pain groups based on maximal pain ratings recorded in a daily diary.

RESULTS

Low levels of dysmenorrhea characterized the first (median, 1; interquartile range, 0-2) and fourth month periods (1; 0-3). Maximal pain ratings increased from the first to the fourth period (3; 1-5 vs 4; 1-6; P=.007). The distribution of dysmenorrhea was multimodal at month 4 with 31.6% of the participants having low levels of maximal pain (1; 0-1) and 68.4% having higher levels (5; 4-6; Hartigan's dip test P<.001). The baseline demographic, psychosocial, and parental pain characteristics were not associated with the development of worse dysmenorrhea. The baseline experimental pain sensitivity, based on pressure pain thresholds, did not differ between the low (15.7 N; 12.5-22.3) and higher (15.0 N; 10.9-21.4]) level dysmenorrhea groups. Baseline bladder pain at first urge also did not differ (low, 6; 0-20 vs higher, 7; 0-19).

CONCLUSION

By their fourth month period, two-thirds of adolescents fell into the higher group for maximal dysmenorrhea, half reported some related impairments in physical activity, and one-seventh reported some related school absence. Premenarchal factors (experimental pain sensitivity, psychosocial profile, parental pain experience) linked to chronic pain emergence in the adult literature did not predict dysmenorrhea intensity, suggesting the dominant factor at menarche may be peripheral afferent activation. Further research is needed to understand the evolution of psychosocial and sensory mechanisms in the development and course of dysmenorrhea.

Acupuncture's long-term impact on depression prevention in primary dysmenorrhea: A 19-year follow-up of a Taiwan cohort with neuroimmune insights

BACKGROUND

Primary dysmenorrhea (PD) is a common gynecological condition causing depression. Acupuncture is an effective option for PD management but its effects on PD-associated depression remain unclear.

METHODS

A retrospective cohort study involving 35,099 propensity score-matched pairs of acupuncture users and non-users with PD was conducted using data from Taiwan's Longitudinal Generation Tracking Database 2000. Cox proportional hazard models were used to estimate depression risk, and bioinformatics analyses were performed to uncover underlying molecular mechanisms.

RESULTS

The risk of developing depression was reduced by 64 % in acupuncture users compared with non-acupuncture users during the 19-year follow-up period. The decrease was dose-dependent. Bioinformatics analyses identified 34 co-expressed targets for acupuncture, PD, and depression; and eight hub genes (coding for interleukin 6 and 1B, tumor necrosis factor, albumin, vascular endothelial growth factor A, C-reactive protein, prostaglandin-endoperoxide synthase 2, and brain-derived neurotrophic factor) potentially involved in the therapeutic effects of acupuncture. Several molecular pathways were found to be involved, including cytokine-cytokine receptor interaction, neuroactive ligand-receptor interaction, cyclic adenosine 3',5'-monophosphate signaling pathway, mitogen-activated protein kinase signaling pathway, serotonergic synapse, and estrogen signaling pathway.

LIMITATIONS

Bias in the selection of participants could have been introduced as a consequence of the retrospective nature of the study. Data were derived from a single national database, and acupuncture treatment details were unavailable.

CONCLUSION

Acupuncture may protect against the development of depression in patients with PD. This study provides insight into the potential molecular mechanisms underlying the therapeutic effects of acupuncture in PD management and depression prevention.

Role of Yoga in Minimizing Stress and Anxiety in Women Experiencing Dysmenorrhea

Primary dysmenorrhea is characterized by recurring, crampy lower abdominal pain occurring during menstruation in the absence of pelvic pathology. It is the most common gynaecological complaint among adolescents. According to the literature, young females with primary dysmenorrhea experience stress, anxiety, lower-back pain, and depression. Yoga is widely practiced to improve health and promote relaxation. It includes breath regulation, simple meditation, and practicing particular body postures. Regular Yoga practice can serve as an adjunct to the primary treatment of dysmenorrhea symptoms. This study focuses on the impacts and benefits of yoga in young females with dysmenorrhea and associated physiological changes.

Primary dysmenorrhoea in adolescents and young women: A twin family study of maternal transmission, genetic influence and associations

AIMS

The extent to which maternal transmission of primary dysmenorrhoea is genetically determined in adolescents and young women has yet to be determined. We aimed to assess heritability and associations relevant to primary pain syndromes using a twin family study.

METHODS

Participants were young menstruating female twins, and their oldest sisters and mothers, whose families were registered with Twins Research Australia and previously participated in a twin family study of primary paediatric pain disorders. Questionnaire packs were mailed, assessing current maximum and average menstrual pain intensity, current pain interference with activities and retrospective dysmenorrhea secondary symptoms.

RESULTS

The sample comprised 206 twin individuals (57 monozygous (MZ) and 46 dizygous (DZ) pairs) aged 10-22 years, eldest siblings (n = 38) aged 13-28 years and mothers (n = 101) aged 32-61 years. The estimated regression coefficient of the relationship between mother-daughter and twin-sibling dyads indicated significant associations for the measures of dysmenorrhea and supported heritability. Adjusted for age, the within twin-pair correlation for MZ twins was generally more than twice that of DZ twins. Heritability estimates were maximal pain intensity 0.67 (P = 3.8 × 10^-11 ), average pain intensity 0.63 (P = 3.7 × 10^-10 ), pain interference 0.57 (P = 1.8 × 10^-8 ) and retrospective symptoms 0.57 (P = 1.8 × 10^-8 ). Twin individuals with a lifetime (three-month) history of iron deficiency and those with painless restless legs syndrome (RLS) were significantly more likely to have more intense pain associated with menstruation.

CONCLUSION

Primary dysmenorrhea in adolescents and young women was shown to be relatively strongly genetically influenced and associated especially with a history of iron deficiency and painless RLS which have potential therapeutic implications.

Genome-wide association study of primary dysmenorrhea in the Taiwan Biobank validates associations near the NGF and IL1 gene loci

Using the Taiwan Biobank, we aimed to identify traits and genetic variations that could predispose Han Chinese women to primary dysmenorrhea. Cases of primary dysmenorrhea included those who self-reported "frequent dysmenorrhea" in a dysmenorrhea-related Taiwan Biobank questionnaire, and those who have been diagnosed with severe dysmenorrhea by a physician. Controls were those without self-reported dysmenorrhea. Customized Axiom-Taiwan Biobank Array Plates were used to perform whole-genome genotyping, PLINK was used to perform association tests, and HaploReg was used to conduct functional annotations of SNPs and bioinformatic analyses. The GWAS analysis included 1186 cases and 24,020 controls. We identified 53 SNPs that achieved genome-wide significance (P < 5 × 10^-8, which clustered in 2 regions. The first SNP cluster was on chromosome 1, and included 24 high LD (R² > 0.88) variants around the NGF gene (lowest P value of 3.83 × 10^-13 for rs2982742). Most SNPs occurred within NGF introns, and were predicted to alter regulatory binding motifs. The second SNP cluster was on chromosome 2, including 7 high LD (R² > 0.94) variants around the IL1A and IL1B loci (lowest P value of 7.43 × 10^-10 for rs11676014) and 22 SNPs that did not reach significance after conditional analysis. Most of these SNPs resided within IL1A and IL1B introns, while 2 SNPs may be in the promoter histone marks or promoter flanking regions of IL1B. To conclude, data from this study suggest that NGF, IL1A, and IL1B may be involved in the pathogenesis of primary dysmenorrhea in the Han Chinese in Taiwan.

Dysmenorrhea subtypes exhibit differential quantitative sensory assessment profiles

Women who develop bladder pain syndrome (BPS), irritable bowel syndrome, or dyspareunia frequently have an antecedent history of dysmenorrhea. Despite the high prevalence of menstrual pain, its role in chronic pelvic pain emergence remains understudied. We systematically characterized bladder, body, and vaginal mechanical sensitivity with quantitative sensory testing in women with dysmenorrhea (DYS, n = 147), healthy controls (HCs) (n = 37), and women with BPS (n = 25). Previously, we have shown that a noninvasive, bladder-filling task identified a subset of women with both dysmenorrhea and silent bladder pain hypersensitivity, and we repeated this to subtype dysmenorrhea sufferers in this study (DYSB; n = 49). DYS, DYSB, and BPS participants had lower vaginal mechanical thresholds and reported more pain to a cold stimulus during a conditioned pain modulation task and greater pelvic examination after-pain than HCs (P's < 0.05). DYSB participants also had reduced body mechanical thresholds and less conditioned pain modulation compared to HCs and DYS participants (P's < 0.05). Comparing quantitative sensory testing results among the DYS and HC groups only, provoked bladder pain was the only significant predictor of self-reported menstrual pain (r = 0.26), bladder pain (r = 0.57), dyspareunia (r = 0.39), and bowel pain (r = 0.45). Our findings of widespread sensory sensitivity in women with dysmenorrhea and provoked bladder pain, much like that observed in chronic pain, suggest a need to study the trajectory of altered mechanisms of pain processing in preclinical silent visceral pain phenotypes to understand which features convey inexorable vs modifiable risk.

Prevalence and Risk Factors Associated with Primary Dysmenorrhea among Chinese Female University Students: A Cross-sectional Study

STUDY OBJECTIVE

To examine prevalence and risk factors associated with primary dysmenorrhea among Chinese female university students in Hunan province, China.

DESIGN

A cross-sectional study.

SETTING

Female university students in Changsha city, Hunan province, China.

PARTICIPANTS

Four thousand six hundred six female individuals selected using a multistage cluster random sampling method.

INTERVENTIONS

A self-administered questionnaire, which included sociodemographic information, lifestyle habits, emotional characteristics, and menstruation pattern, was used to collect data.

MAIN OUTCOME MEASURES

Information about menarche, body mass index, cycle length and regularity, primary dysmenorrhea, physical exercise, depression, and anxiety.

RESULTS

The prevalence of primary dysmenorrhea was 41.7% (1921/4606) among Chinese female university students. Multivariate binary logistic regression indicated that being a minority (odds ratio [OR], 1.335; 95% confidence interval [CI], 1.083-1.646), underweight (OR, 1.249; 95% CI, 1.08-1.42), annual household income less than 80,000 CNY (OR, 1.169; 95% CI, 1.018-1.342), maternal history of dysmenorrhea (OR, 2.553; 95% CI, 2.236-2.915), age at menarche younger than 12 years (OR, 1.161; 95% CI, 1.013-1.329), irregular menstrual cycle (OR, 1.216; 95% CI, 1.063-1.391), and skipping breakfast (OR, 1.294; 95% CI, 1.124-1.490) were associated risk factors of primary dysmenorrhea.

CONCLUSION

The prevalence of primary dysmenorrhea among Chinese university students is relatively high. Various risk factors were identified that associated with primary dysmenorrhea. More effort and attention should therefore be directed toward this health problem in China.

Menstrual Pain: A Review of Foreign Literature

The World Health Organization estimates dysmenorrhea as the most important cause of a chronic pelvic pain. Its prevalence among adolescents and young women ranges from 40 % to 90 %, and varies, depending on age, country of residence and population density of the area. Primary dysmenorrhea is responsible for reducing the quality of life, absenteeism in the workplace or at school, refusing to participate in community and sporting events, changing of pain perception and sleep disturbance. There is evidence of its relationship with an early menarche, a family history, a length of the menstrual cycle, bad habits, poor sleep hygiene, an unbalanced diet, sedentary lifestyle and obesity. Characteristic features of a personality contribute in a certain way, making women prone to neuroticism and pain catastrophizing to be more at risk of developing dysmenorrhea. Irritable bowel syndrome, musculoskeletal pain and interstitial cystitis often accompany dysmenorrhea and respond to its treatment positively. Despite the proven validity of nonsteroidal anti­inflammatory drugs treatment there are resistant forms of menstrual pain, those make a search for alternative therapy relevant.

Somatic symptoms in women with dysmenorrhea and noncyclic pelvic pain

Somatic symptoms are a robust, transdiagnostic risk factor for pain conditions. However, the extent to which somatic symptoms contribute to the manifestation of the women's pain syndromes, such as dysmenorrhea and noncyclic pelvic pain (NCPP), is unclear due to high rates of co-occurrence. Therefore, the present study investigated the primary hypothesis that somatic symptoms would be elevated in NCPP and distinctly influence the relationship between dysmenorrhea and co-occurring NCPP. A secondary analysis was performed on cross-sectional questionnaire data from 1012 nonpregnant reproductive-aged women. Eligible analyzed participants (n = 834) were categorized into four groups: healthy, dysmenorrhea, NCPP, and NCPP with co-occurring dysmenorrhea (NCPP+dysmenorrhea). A parallel mediation analysis was run to evaluate the primary hypothesis that somatic symptoms are the primary factor associated with increased NCPP accounting for dysmenorrhea. The NCPP+dysmenorrhea group had higher somatic, anxiety, and depression symptom T-scores (respectively 61, 61, 60) compared to the healthy controls (46, 51, 51; p's < .001) and the dysmenorrhea group (50, 53, 54; p's < .001). The pain and psychological symptoms were significantly correlated across the entire sample (r's = .29, - .64, p's < .01). Results from parallel mediation analysis showed that somatic symptoms were distinctly associated with NCPP+dysmenorrhea. Women with NCPP+dysmenorrhea have increased psychological and somatic symptoms compared to women with dysmenorrhea alone. Given that NCPP often co-occurs with dysmenorrhea, failure to account for comorbidity in previous studies has likely led to an overestimation of psychological symptoms in dysmenorrhea. Future studies should evaluate whether somatic sensitivity is a modifiable risk factor for NCPP.

Lifestyle and prevalence of dysmenorrhea among Spanish female university students

The aim of this study was to determine the prevalence of primary dysmenorrhea in a sample of Spanish university students, and to describe their menstrual characteristics, lifestyle habits and associated risk factors. This cross-sectional study was conducted with a total of 258 young female university students recruited from the Ciudad Real Faculty of Nursing, with a mean age of 20.63± 3.32 years. An anonymous self-report questionnaire was used to collect data from students. This included sociodemographic characteristics, lifestyle habits, gynecological personal history and the severity of pain using the visual analogue scale. The statistical analysis of the data included calculation of the mean, percentages, chi-square analysis of the data and logistic regression. The prevalence of dysmenorrhea was of 74.8% (n = 193) with a mean pain severity of 6.88 (±1.71). Our results show that 38.3% of students described their menstrual pain as severe and 58% as moderate. The bivariate analysis showed statistically significant differences between students with and without dysmenorrhea: a higher proportion of women with dysmenorrhea had a greater duration of the menstruation flow (p = .003), a longer duration of the menstrual cycle (p = .046), were not using the oral contraceptive pill (p = .026) and had a family history of dysmenorrhea (p = .001). Backward step-wise binary logistic regression analysis using all the significant bivariate variables including lifestyle variables revealed the following risk factors: drinking cola drinks, duration of the menstrual flow, eating meat and having a first-degree relative affected by dysmenorrhea.

Common variants in ZMIZ1 and near NGF confer risk for primary dysmenorrhoea

Primary dysmenorrhoea, defined as painful menstrual cramps in the absence of pelvic pathology, is a common problem in women of reproductive age. Its aetiology and pathophysiology remain largely unknown. Here we performed a two-stage genome-wide association study and subsequent replication study to identify genetic factors associated with primary dysmenorrhoea in a total of 6,770 Chinese individuals. Our analysis provided evidence of a significant (P<5 × 10⁻⁸) association at rs76518691 in the gene ZMIZ1 and at rs7523831 near NGF. ZMIZ1 has previously been associated with several autoimmune diseases, and NGF plays a key role in the generation of pain and hyperalgesia and has been associated with migraine. These findings provide future directions for research on susceptibility mechanisms for primary dysmenorrhoea. Furthermore, our genetic architecture analysis provides molecular support for the heritability and polygenic nature of this condition.

Primary dysmenorrhoea, the most common gynaecologic complaint, remains genetically and pathophysiologically elusive. Here, Li and colleagues identify common variants in ZMIZ1 and near NGF conferring risk for primary dysmenorrhoea using genome-wide association study in a Chinese population.

Prevalence of Primary Dysmenorrhea and Factors Associated with Its Intensity Among Undergraduate Students: A Cross-Sectional Study

Primary dysmenorrhea is a womanhood problem around the world and negatively affects quality of life. This study was designed to investigate the prevalence of primary dysmenorrhea and to determine the factors associated with its intensity. A cross-sectional study was carried out among 311 undergraduate female students aged 18 to 27 years in Isfahan University of Medical Sciences, Iran. Socio-demographic characteristics and menstrual factors were obtained through interviews with the help of a pretested questionnaire. The prevalence of primary dysmenorrhea was 89.1%. Residing at home, younger age, lower number of years of formal education for the mother, positive family history of dysmenorrhea, higher severity of bleeding, and shorter menstrual period intervals were significantly associated with the higher intensity of primary dysmenorrhea. Primary dysmenorrhea is a common health concern among young women. Being aware of the factors that are associated with its intensity makes it possible for health professionals to organize better focused programs to reduce the adverse effects of dysmenorrhea.

A noninvasive bladder sensory test supports a role for dysmenorrhea increasing bladder noxious mechanosensitivity

OBJECTIVE

Catheterization to measure bladder sensitivity is aversive and hinders human participation in visceral sensory research. Therefore, we sought to characterize the reliability of sonographically estimated female bladder sensory thresholds. To demonstrate this technique's usefulness, we examined the effects of self-reported dysmenorrhea on bladder pain thresholds.

METHODS

Bladder sensory threshold volumes were determined during provoked natural diuresis in 49 healthy women (mean age, 24±8 y) using 3-dimensional ultrasound. Cystometric thresholds (Vfs, first sensation; Vfu, first urge; Vmt, maximum tolerance) were quantified and related to bladder urgency and pain. We estimated the reliability (1-wk retest and interrater). Self-reported menstrual pain was examined in relationship to bladder pain, urgency, and volume thresholds.

RESULTS

Average bladder sensory thresholds (mL) were Vfs (160±100), Vfu (310±130), and Vmt (500±180). Interrater reliability ranged from 0.97 to 0.99. One-week retest reliability was Vmt=0.76 (95% CI, 0.64-0.88), Vfs=0.62 (95% CI, 0.44-0.80), and Vfu=0.63 (95% CI, 0.47-0.80). Bladder filling rate correlated with all thresholds (r=0.53 to 0.64, P<0.0001). Women with moderate to severe dysmenorrhea pain had increased bladder pain and urgency at Vfs and increased pain at Vfu (P's<0.05). In contrast, dysmenorrhea pain was unrelated to bladder capacity.

DISCUSSION

Sonographic estimates of bladder sensory thresholds were reproducible and reliable. In these healthy volunteers, dysmenorrhea was associated with increased bladder pain and urgency during filling but unrelated to capacity. Plausibly, women with dysmenorrhea may exhibit enhanced visceral mechanosensitivity, increasing their risk to develop chronic bladder pain syndromes.

Genetic and environmental determinants of menstrual characteristics

BACKGROUND

The impact of women's menstrual cycle on her quality of life, health, work, and community is substantial. Menstrual disturbance is linked with general ill conditions such as migraine, asthma, and endocrinopathies. The clinical significance of medical interventions to prevent these conditions becomes clear if the role of genetic or environment is clarified.

AIMS

To identify the genetic and environmental contribution on menstrual characteristics.

SETTING AND DESIGN

This was a cross-sectional study in 2 Asian countries.

MATERIALS AND METHODS

2 cohorts of monozygotic and dizygotic twins born between (1945-1988, n = 122) and (1951-1993, n = 71) were taken. A standard questionnaire was designed inclusive of socio- demographic characteristics of subjects as well as menstrual history (duration, interval, amount, irregularity). Subjects were interviewed by phone.

STATISTICAL ANALYSIS

Quantitative variables were analyzed using Falconars' formula as well as maximum likelihood analysis. Structural modeling was then applied to twin correlations to provide estimates of the relative genetic and/or environmental factors contribution in determining the measured trait.

RESULTS

Menstrual characteristics were found to be under environmental influence where the best fitting model for menstrual interval and duration was common environment. CDF plotting confirmed the results for both variables. Proband-wise concordance analysis for amount of menstruation, amenorrhea, and irregular menstruation revealed no genetic influence. The best fitting model for menstrual irregularity was CE (C73%, E27%). The same model was defined for amenorrhea (C48%, E52%).

CONCLUSIONS

Environmental factors are most likely responsible to determine the menstrual flow, its integrity, and regularity. These factors need to be studied further.

Menstrual Pain Intensity, Coping, and Disability: The Role of Pain Catastrophizing

OBJECTIVE

Menstrual pain or primary dysmenorrhea has not received much attention in the field of pain research. Little is understood about the effects menstrual pain has on the women who experience it. No studies to date have examined the cognitive factors related to the perceived intensity and coping of menstrual pain. To investigate these areas further, this study examined the associations between pain catastrophizing and how women perceive and cope with menstrual pain.

DESIGN

A prospective and retrospective between-subjects study.

PARTICIPANTS

Ninety-three undergraduate women, with a regular menstrual period and no preexisting pain disorder (e.g., endometriosis) that affects menstrual pain, were classified into high or low pain catastrophizing groups.

OUTCOME MEASURES

Participants completed several self-reported questionnaires assessing pain catastrophizing, menstrual pain intensity, coping, and disability.

RESULTS

High pain catastrophizers, in comparison with low pain catastrophizers, reported greater menstrual pain intensities, greater affective menstrual pain intensity, greater variability in the use of pain coping strategies, lower perceived effectiveness of over-the-counter medications and nonmedical pain coping strategies, and greater disability.

CONCLUSIONS

The results extend our knowledge about the associations between pain catastrophizing and menstrual pain, reemphasize that pain experience is best viewed as a multidimensional construct, and have implications for the management of menstrual pain.

Genetic influences on endometriosis in an Australian twin sample. sueT@qimr.edu.au

OBJECTIVE

To investigate the prevalence of and twin pair concordance for endometriosis.

DESIGN

A questionnaire survey incorporating validation.

SETTING

An Australia-wide volunteer sample of female monozygotic (MZ) and dizygotic (DZ) twin pairs from the Australian National Health and Medical Research Council Twin Register.

PATIENT(S)

Twins were selected only on the basis of previous participation in twin research.

INTERVENTION(S)

Questionnaires were sent to 3,298 individuals. Information was requested from physicians named by consenting twins.

MAIN OUTCOME MEASURE(S)

Reported endometriosis, validated where possible by pathology or surgical report.

RESULT(S)

Three thousand ninety-six (94%) of the twins and 145 (82%) of the physicians responded to the survey. Two hundred fifteen twins reported endometriosis, for a prevalence rate of .07 among question respondents. Tetrachoric twin pair correlations for self-reported endometriosis (MZ: n = 854 and DZ: n = 493) were rMz = .46+/-.09 and rDz = .28 +/-.13. When available medical and pathology reports were included, they changed to rMz =.52 +/-.08 and rDZ = .19+/-.16, suggesting that 51% of the variance of the latent liability to endometriosis may be attributable to additive genetic influences.

CONCLUSION(S)

These findings support the hypothesis that genes influence liability to endometriosis.

Genetic and environmental factors in the aetiology of menstrual, premenstrual and neurotic symptoms: a population-based twin study

Symptoms during the premenstrual and menstrual phases of the female reproductive cycle were assessed in 827 pairs of female same-sex twins from a population-based registry. By conventional factor analysis, premenstrual and menstrual symptoms were relatively independent of one another and of baseline 'neurotic' symptoms (i.e. anxiety, depression and somatization). Familial resemblance for menstrual and premenstrual symptoms was due solely to genetic factors with heritability estimates of 39.2% and 35.1%, respectively. Multivariate genetic analysis revealed distinct genetic and environmental factors for menstrual, premenstrual and neurotic symptoms. The genes and individual-specific experiences that predispose to premenstrual symptoms appear to be largely distinct from those which predispose either to menstrual or to neurotic symptoms. The generalizability of these results may be limited because only a modest number of premenstrual and menstrual symptoms were assessed, all by retrospective self-report.

Genetic and environmental effects on self-reported depressive symptoms in a general population twin sample

To determine the etiology of self-reported depressive symptoms and their co-occurrence in the general population, multivariate genetic models were fitted to the responses of 771 female twin pairs (463 MZ, 308 DZ) to a 20-item epidemiological depression inventory (CES-D scale). A model which contained one common genetic factor, one shared environmental factor, and four unique environmental factors provided a useful account of symptom covariation. Under this model, the four non-shared environmental factors explained the largest proportion of variance in response to the CES-D scale, whereas a single common genetic factor explained substantially less of the variation in symptomatology. Consistent with previous findings (Kendler, Heath, Martin, & Eaves, Archives of General Psychiatry 43, 213-221, 1986) shared environmental influences were found to play a relatively minor role in the report of depressive symptoms. These results suggest that while genetic factors do contribute to the covariation among symptoms of depression, it is the largely non-shared environmental factors that account for the co-occurrence of symptoms in the general population.

Testing structural equation models for twin data using LISREL

Simple genetic models can be fitted to twin data using software packages such as LISREL (Jöreskog and Sörbom, 1986a). After discussion of data preparation and routine checks on possible violation of assumptions of the twin method, we illustrate univariate, bivariate, and multivariate genetic models which can be tested in cross-sectional twin data using LISREL. These include models for cohort or cohabitation effects, genotype x sex interaction, and certain types of genotype x environment interaction and genotype-environment correlation.

Anxiety disorders and neuroticism: are there genetic factors specific to panic?

Data from 2,903 adult same-sex twin pairs were analysed to investigate whether the genetic determinants of symptoms of panic are different from those underlying the neuroticism personality trait. Our results suggest that much of the genetic variation influencing the physical symptoms associated with panic is of the nonadditive type, perhaps due to dominance or epistasis. In both sexes these nonadditive genetic effects on physical symptoms influence the reporting of "feelings of panic". In males they also account for as much as half the genetic variance in neuroticism. The remainder is additive and also accounts for the balance of genetic variation in "feelings of panic". In females genetic variance in neuroticism is entirely additive but is not an important source of covariation with either panic symptom. Thus, symptoms of panic seem to be shaped in part by unique genetic influences which do not affect other anxiety symptoms. That a substantial part of the genetic variance in neuroticism in males may be due to the nonadditive effects on physical symptoms of panic may help to explain the rather low correlation between the genetic influences found to affect neuroticism in males and their counterparts in females.