General causal models for sex differences in the familial transmission of multifactorial traits: an application to human spatial visualizing ability

A general multifactorial model is given for the inheritance of traits that exhibit a sexual dimorphism. The model allows for polygenic inheritance, cultural transmission, phenotypic assortative mating, and a common environment of rearing. Several cultural mechanisms are described for which transmission from parent to offspring is sex-dependent and for which many different patterns of sex-specific correlations can result. A special case of the general model is described in which phenotypic differences between males and females are due only to differences in nontransmissible environmental factors and/or genetic factors that do not contribute to variability within a sex. Application of these models to human spatial visualizing ability, using data reported by others, gives an estimate of 45 per cent for the proportion of the variance that is accounted for by transmissible factors. Neither an X-linked hypothesis nor a sex-specific cultural mechanism is required to explain the transmission of spatial ability.

Analysis of behavioral traits in the presence of cultural transmission and assortative mating: Applications to IQ and SES

General linear models of familial resemblance are described which allow for polygenic inheritance, cultural transmission from parent to offspring, phenotypic assortative mating, common environment, and maternal and parental effects. These models use observed phenotypic correlations between multiple classes of relatives and/or correlations between individuals reared in separated and extended family structures to yield maximum likelihood parameter estimates. The models are first applied to American kinship data for IQ, with the variance of IQ partitioned as 30% additive genetic, 29% due to cultural inheritance, 9% due to gene--culture covariance, and 32% due to nontransmissible environment. Under the assumption that the correlations between (nontransmissible) environments of DZ and MZ twins are the same, an approximate treatment of dominance yields an estimate of 23% dominance variation.

The natural history of acute organic mental syndrome after bilateral electroconvulsive therapy

Thirty-one patients undergoing electroconvulsive therapy (ECT) were followed prospectively for the development of acute organic mental syndrome (AOMS); 15 patients (48.4%) developed AOMS during ECT. For these 15 patients, the average number of ECTs before development of AOMS was 5.5 with average duration of AOMS being 20.1 days. Comparison of these 15 patients to the 16 patients who did not develop AOMS for diagnoses, demographic data, pre-ECT laboratory data, and medications, differed only in exposure to psychoactive medications and prior presence of major medical illness.

Is juvenile diabetes determined by a single gene closely linked to HLA?

The transmission behavior of insulin-dependent juvenile diabetes mellitus (JDM) has been studied with respect to its frequency in the relatives of JDM probands and its possible linkage to the HLA complex. Mathematical analysis shows that under a single locus hypothesis a very restricted range of incidence rates is possible in the full siblings of probands once the concordance rate in monozygotic (MZ) twins is specified. Specifically, for a given population prevalence of the disease, high concordance rates in MZ twins require high incidence rates in siblings, and low rates require low incidence rates, if a single locus model is th be valid. Moreover, if these rates do conform to a single locus model, then they give additional information about possible linkage between the purported JDM susceptibility gene and the HLA complex. By using observations on the identity by descent scores at the HLA locus of sibling pairs, both of whom are affected with JDM, it is shown that tight linkage of a disease susceptibility locus is possible only when the MZ twin and sibling incidence rates are low, whereas high rates support loose linkage. If the single locus model is rejected, then an alternative hypothesis, involving epistasis between a JDM susceptibility locus and genes in (or close to) the HLA complex can be suggested as a mechanism whereby JDM would appear to be linked to HLA within families while maintaining an association with HLA at the population level.

Multifactorial inheritance with cultural transmission and assortative mating. III. Family structure and the analysis of separation experiments

Demographic data about family composition or structure in the United States is reviewed. About 25% of white children and a majority of black children are reared in either broken or extended families, and this must be taken into consideration for valid studies of cultural inheritance. Atypical family structures are described including those in which parents include: biological parents, stepparents, grandparents, uncles, aunts, sibs, foster parents, and their spouses. General formulae for a wide variety of kinship correlations are derived using path analysis. The multifactorial model presented allows for cultural inheritance, polygenic inheritance, correlated sibling environments, and phenotypic assortative mating (as previously described for intact families) plus extensions necessary for the analysis of separation experiments. These extensions allow for variable family structure and differences in parental influence due to separation, age or stage of development of the child, birth order, or type of relationship. Family structure is observed to have a marked effect on familial resemblance. Computer simulation studies demonstrate marked heterogeneity among phenotypic correlations for kinships of the same degree of genetic relationship arising in different family structures. Analyses of multiple types of sibs and other relatives in variable family structures offer great promise for the study of cultural inheritance.

The management of patients with undiagnosed psychiatric illness

The results of using formal diagnostic criteria on a series of newly admitted inpatients are presented. Several strategies were employed in the management of the undiagnosed patients. The percent of undiagnosed patients significantly decreased with time during the course of hospitalization.

Multifactorial inheritance with cultural transmission and assortative mating. II. a general model of combined polygenic and cultural inheritance

A general linear model of combined polygenic-cultural inheritance is described. The model allows for phenotypic assortative mating, common environment, maternal and paternal effects, and genic-cultural correlation. General formulae for phenotypic correlation between family members in extended pedigrees are given for both primary and secondary assortative mating. A FORTRAN program BETA, available upon request, is used to provide maximum likelihood estimates of the parameters from reported correlations. American data about IQ and Burks' culture index are analyzed. Both cultural and genetic components of phenotypic variance are observed to make significant and substantial contributions to familial resemblance in IQ. The correlation between the environments of DZ twins is found to equal that of singleton sibs, not that of MZ twins. Burks' culture index is found to be an imperfect measure of midparent IQ rather than an index of home environment as previously assumed. Conditions under which the parameters of the model may be uniquely and precisely estimated are discussed. Interpretation of variance components in the presence of assortative mating and genic-cultural covariance is reviewed. A conservative, but robust, approach to the use of environmental indices is described.

The use of multiple thresholds and segregation analysis in analyzing the phenotypic heterogeneity of multifactorial traits

(1) Three models based on multifactorial inheritance are introduced to account for phenotypic heterogeneities. These models are used to determine whether subforms of a triat are: (a) different degrees of the same process, (b) non-familial environmental variants of the same process, and (c) independently transmitted processes. (2) The parameters of each model consist of two population prevalences and either one, two, or three correlation coefficients which reflect the three hypotheses given above. The models are formulated so that a likelihood ratio test may be performed to discriminate between them. (3) The following types of analyses are described: (a) analysis of prevalence data with separate population prevalence estimates, (b) analysis of prevalence data with the proband a parent with specified spouse, (c) analysis of prevalence data with the proband an offspring with specified parents, and (d) the full segregation distribution of families using Complex Segregation Analysis. (4) When compared with the Analysis of Prevalences, Complex Segregation Analysis has the following advantages: (a) the number of degrees of freedom for parameter estimates is greater and separate estimates of the population prevalences are not necessary, (b) standard errors of the parameters are smaller, and (c) the power to discriminate models is increased. (5) Phenotypic heterogeneities such as age of onset, severity, and sex effect can be more completely understood by the methods of analyses described above. The nosology of familial disorders can also be clarified, and environments relevant to the transmission of the trait can be detected. This approach is particularly suitable for the analysis for behavioural traits since it does not require the assumption that environmental effects common to relatives be ignored. (6) Finally, our experience indicates that incorporating both prevalence and pedigree data into a single analysis decreases the time required to perform the analysis.

Variability in sib pair genetic identity

Using a realistic model of meiotic crossing over the variability in full sib genetic identity is estimated by simulating 200 independent pairs of sibs. The standard deviation of the percentage of the autosomal genome identical by descent (IBD) was found to be about 0.056. Simulations of sibships larger than size two revealed that the average within sibship standard deviation is between 0.054 and 0.056, thus indicating that sib pair variability is insensitive to the nonindependence structure present when considering all possible sib pairs contained in a large sibship.

Multifactorial inheritance with cultural transmission and assortative mating. I. Description and basic properties of the unitary models

A general linear model of familial resemblance is described which allows for cultural transmission from parent to offspring, polygenic inheritance, phenotypic assortative mating, common environment, maternal and paternal effects, and threshold effects. Three special cases are described in detail which are particularly useful when data are only available about a few classes of relatives reared in intact families. The cultural model, the polygenic model, and the pseudopolygenic model share the common feature that all factors which are transmitted from parent to offspring may be represented by one parameter without any loss of information. We introduce a new model, termed the unitary model, which includes these models and is appropriate when combined genetic and cultural transmission is present and when data are available only for individuals reared in intact nuclear families. The basic properties of these models are explored using path analysis and computer simulation, including description of the relationship between parameters under random and assortative mating, rate of approach to equilibrium, and constraints on the magnitude of the parameters. General formulae for familial resemblance in extended pedigrees are given for any ancestor or descendant of either vertical or collateral relatives. Estimation procedures are described and a FORTRAN program TAU, available upon request, is used to provide maximum likelihood estimates of the parameters from reported correlations. A powerful test for detecting the presence of cultural transmission is suggested and applied to simulated data and to data sets reported by others for human stature, for which cultural transmission is suggested. In addition, it is shown that there is no need to postulate dominance to account for available data about height.

Implications of sex differences in the prevalences of antisocial personality, alcoholism, and criminality for familial transmission

We describe three multifactorial models of disease transmission in which the prevalences of a disease differ in men and women. These models demonstrate explicitly how such sex differences may be caused by genetic factors, home environment, sociocultural, or other nonfamilial factors. Independent sets of family data about antisocial personality and alcoholism in the United States and criminality in Danish twins are analyzed according to these quantitative models. Relevant clinical and adoption data about these disorders are reviewed. The sex differences observed in the development of antisocial personality and of crime appear to be due to familial factors whereas the differences between male and female alcoholics are due to nonfamilial factors. The models and results are discussed in terms of their general implications for testing hypotheses about gender-related differences.

The generalized sib pair IBD distribution: its use in the detection of linkage

General expression for the distribution of identity by descent (IBD) scores at a marker locus have been derived given neither, one or both sibs affected with a disorder determined by a linked trait locus with arbitrary gene frequency and penetrance vector. It is shown that the distirbution of IBD scores depends only on the additive and dominance variances and the population prevalence of the disorder. A one-sided test is suggested as an appropriate means of statistically testing the hypothesis that the recombination fraction is significantly less than 1/2. This sib pair approach is designed primarily to detect the presence of a critical disease susceptibility locus but when the assumptions of the incompletely penetrant single locus model are correct the methodology proposed here results in consistent estimates of the recombination fraction. The affected sib pair methodology seems especially suited to traits determined by single loci with non-Mendelian transmission.

A robust method for the detection of linkage in familial disease

A nonparametric method for the detection of critical genes associated with familial disease was presented. The method involves the detection of deviations from expected identity by descent distributions at polymorphic marker loci for affected sib pairs. The method thus avoids the difficulties arising from incomplete penetrance, variable age of onset and other complications present in other forms of linkage analysis. The theoretical properties of method were worked out in detail for two important cases -- that of an incompletely penetrant recessive or incompletely penetrant dominant critical autosomal gene linked to a codominant marker locus. An easily implementable decision rule for the detection of linkage was proposed, and its operating characteristics for a variety of alternative hypothesis were obtained.

A note on the essential parameters of the two-allele autosomal locus model

A resolution of the parameter problem for the two-allele autosomal locus (TAAL) model has been presented. It was shown that three are four essential parameters which describe the model, by examination of the joint probability for sibs with specified parental phenotypes. This equation together with previously derived prevalence relationships uniquely specifices all parameters of the model except for the singular case VA = 0.

[Variation of morphometric measurements in bone biopsies (author's transl)]

The variation of histomorphometric data in a bone biopsy cylinder of the iliac crest was determined in order to derive a rule of the sampling procedure in such a biopsy specimen. Measurements in different cylinders of a biopsy zone in the right and the left iliac crest were obtained in order to determine the magnitude of change necessary for the recognition of therapeutic or spontaneous alterations performing sequential biopsies.

Cyclandelate: effect on circulatory measurements and exercise tolerance in chronic arterial insufficiency of the lower limbs

Thirty-nine patients with arterial insufficiency of the lower limbs were treated with cyclandelate or placebo in a double-blind cross-over study, to evaluate the effect of this drug on symptomatic and physiologic indicators of circulatory status. The following measurements were used: skin temperature of the big toe and dorsum of the foot; blood flow in the calf at rest and after exercise on a foot ergometer to the point of claudication; walking distance to the development of claudication; exercise tolerance on a foot ergometer; and reflex vasoconstriction on the skin of the toe in response to cooling of the upper extremities. During treatment with cyclandelate, significant improvement occurred in each of these measures of circulatory efficiency.

Reliability of psychiatric diagnosis. II. The test/retest reliability of diagnostic classification

In a study of interrater diagnostic reliability, 101 psychiatric inpatients were independently interviewed by physicians using a structured interview. Newly admitted patients were randomly selected and examined by one of three psychiatrists. A second psychiatrist reexamined the same patient about 24 hours later. Interviews from the two examinations were evaluated independently and diagnoses were made on the basis of objective criteria. The degree of diagnostic agreement for the two examinations were calculated using the kappa statistic. Agreement was found to be high as compared to other studies in the psychiatric literature, despite the fact that in most previous investigations diagnoses were not made independently. The results were also compared to studies of reliability of medical judgments. Possible reasons for the high interrater reliability are discussed and include the use of a structured interview and objective diagnostic criteria.

Reliability of psychiatric diagnosis. I. A methodological review

This article reviews some methodological aspects of studies of diagnostic reliability in psychiatry. We define and discuss the concept of interrater reliability and review some of the ways in which the design of the reliability study can influence the results. Three basic methodological issues are raised, including: importance of structured interviews and objective diagnostic criteria, the importance of a test/retest vs an interviewer/observer design, and the calculation of reliability in a way that takes chance agreement into account.

Evaluation of a screening interview for Briquet syndrome (hysteria) by the study of medically ill women

A screening interview for Briquet syndrome consisting of 14 symptom questions was administered to a group of 50 medically ill women. No patient was found eligible for a diagnosis of Briquet syndrome, a frequency less than the estimated general population prevalence of 1% to 2%. When symptoms explainable by known organic disorder were considered positive, 14% of patients became eligible for the diagnosis. We consider this a low enough rate to allow screening by lay interviewers. A frequency distribution of symptoms comparing the medically ill women and a group of psychiatric clinic women with Briquet syndrome shows that the Briquet group had both more symptoms and distinctive patterns of symptoms.

Estimating the parameters of the incompletely penetrant single locus model using multiple populations

A method involving the comparison of two or more populations is suggested as a means of obtaining a unique solution to the parameters of the incompletely penetrant single locus model. The proposed method allows a test of the assumptions of the model when three or more populations are compared. Equations that allow the inclusion of data on twin concordance rates and/or the proportion of affected children given neither, one or both parents affected are also given. Finally, some implications of fitting the model are discussed in terms of genetic counseling, residual environmental variance and the concept of heritability as applied to dichotomous traits.

[Problems regarding gasometric analysis when umbilical cord blood specimens are stored (author's transl)]

If, as is often the case in routine practice, the gasometric analysis cannot be conducted immediately after withdrawal of the blood specimen, this does not have important consequences for the clinical. When the blood specimens are stored in open glass tubes, the alterations are all within the demands made of the method for measurement accuracy. As far as the purely clinical problem is concerned, it would even be possible to let the umbilical cord itself set for up to 90 minutes. Discrepancies between the gas status from blood specimens measured late and the Apgar score cannot be explained by storing and, insofar as errors in measurement are not involved, can represent an important piece of informations for the diagnosis of the condition of the newborn.

Limits of the general two-allele single locus model with incomplete penetrance

A graphical method is presented that allows an investigator to find the mathematical limits of the general one locus two allele genetic model for any trait whose population prevalence is known. It is seen that while the model is quite flexible in its ability to fit family data, there remains a large area where the model cannot be fitted. Specific sub-regions corresponding to particular hypotheses (e.g. underdominant v. intermediate v. overdominant) can be found, thereby limiting the area that needs to be searched by other more complicated techniques. Moreover, knowledge of where a set of observations lies can enable an investigator to frame and test specific subhypotheses.

Calf blood flow in intermittent claudication

Calf blood flow was correlated with severity of symptoms in 24 patients with intermittent claudication. Calf blood flow was measured (Whitney strain gauge) at three levels of demand--at rest, after exercise ("open"), and after exercise with total vascular occlusion by a tourniquet about the thigh ("closed"). The results showed significant correlation between the patients' reported capacity to walk and measured exercise tolerance on an ergometer (P less than or equal to .01). The coefficients of correlation between exercise tolerance and calf blood flow (resting, postopen or postclosed exercise) or the vascular reserve (difference between postopen and postclosed exercise hyperemia) were not significant. It is concluded that capacity for walking in cases of intermittent claudication is not a reliable index of the calf blood flow. The relationship between these factors would be clearer if the patients pain threshold and calf tissue metabolic activity were known also.

Organic brain dysfunction as a possible consequence of postgastrectomy hypoglycemia

Unlike the fasting hypoglycemias, the reactive hypoglycemias, including postgastrectomy hypoglycemia, are generally not believed to result in serious neuropsychiatric dysfunction. The authors describe two patients with progressive mental deterioration and alimentary hypoglycemia and suggest that clinicians should recognize the possibility of serious neuropsychiatric sequelae of postgastrectomy hypoglycemia.

Premenstrual affective syndrome and affective disorder

Sixty-four per cent of 874 freshmen and sophomore women sent questionnaires about premenstrual and menstrual symptoms returned them. They differed from those not returning the questionnaires only in year of school. As predicted, women reporting premenstrual affective symptoms were more likely than those who did not report them to seek psychiatric care at the Student Health Service and to be diagnosed as affective disorder at the service.

The multifactorial model of disease transmission: III. Familial relationship between sociopathy and hysteria (Briquet's syndrome)

Hysteria (Briquet's Syndrome) and sociopathy cluster in the same families instead of segregating as independent traits. Assortative mating between hysterics and sociopaths increases the observed similarity between relatives, but the familial association between sociopathy and hysteria remains after taking assortative mating into account. The Multifactorial Model of Disease Transmission with three thresholds related to severity and sex accounts for population and family data about sociopathic men, sociopathic women, and women with hysteria. The data were obtained for 227 first-degree relatives and for 800 subjects in the general population.

Depending on the sex of the individual and its severity, the same aetiological process may lead to different, sometimes overlapping, clinical pictures. Specifically, analysis indicates that hysteria in women is a more prevalent and less deviant manifestation of the same process that causes sociopathy in women.

The multifactorial model of disease transmission: II. Sex differences in the familial transmission of sociopathy (antisocial personality)

Sociopathy is highly familial in both white and black families. Sociopathy in men and women clusters in the same families, but is much more frequent in men than in women. It is more prevalent among relatives of sociopathic women than among relatives of sociopathic men. The sex difference in its prevalence appears to be due to sex-related cultural or biological factors causing the threshold to be more deviant in women. There is no evidence of a genetic difference in its prevalence and transmission according to race.

The two-threshold Multifactorial Model of Disease Transmission provides an explanation for the striking sex difference in the transmission of sociopathy. Such a pattern of transmission is obtained only in diseases whose genetic component is polygenic or, if only one or a few genotypes are relevant, where each of these has a small effect relative to environmental factors.

Assortative mating accounts for a large proportion of the observed similarity between relatives. However, the familial clustering of male and female sociopaths is not dependent on assortative mating.

The high correlation among siblings that is expected under conditions of random mating indicates that environmental factors common to siblings contribute to the aetiology of sociopathy. The greater deviance of the parental home experiences of sociopathic women compared to sociopathic men is further evidence of the importance of familial environment.