The assumptions and properties of the Multifactorial Model of Disease Transmission are described, using the principles of quantitative genetics. No assumptions are made about the relative importance of genetic and environmental factors in the transmission of a disorder. The usefulness of the Model is discussed as a device for quantifying family data, discriminating between different modes of transmission and studying variations in disorders according to such clinical variables as age, sex, and severity of illness.

When only one form of a disorder can be distinguished, the degree to which the disorder is transmissible can be measured, and the relative importance of familial factors in the aetiology can be assessed. The assumptions which underlie the Model cannot be tested.

When two or more forms of a disorder can be distinguished, family and population data can be used to test the underlying assumptions of the Model. A good fit of the Model to the observed data indicates that the two subforms of the disorder represent different degrees of the same normally distributed process. This implies that the relative importance of transmissible and non-transmissible factors is the same in determining each subform of the disorder. The testability of the Multifactorial Model with multiple thresholds offers an opportunity for relating and understanding heterogeneous subforms of a disorder, for specifying the relationship between spectrum disorders, and for classifying psychiatric disorders.

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.

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.

A battery of psychological tests was administered on three occasions over a three-month period to 75 patients admitted to a geriatric hospital and 75 patients admitted to psychiatric hospitals serving the same catchment area. The test results, used as an independent criterion, provided evidence that the criteria of psychiatric diagnosis were applied with constancy and accuracy in the two types of hospital, and supported the psychiatrists' findings that there were no strong grounds to believe that elderly patients were being ‘misplaced’ in one or other type of hospital facility.

In a controlled trial, ‘reality orientation’ for elderly patients diagnosed as suffering from dementia is shown to be effective only where therapists actively participate. Exposure to change in a more stimulating environment than their own wards is not enough to produce sustained improvement.

A study of familial and social factors among Jewish and Protestant depressives and non-psychiatric controls revealed the following positive findings:

Depressives compared to normals as a whole had: (a) a higher rate of psychiatric illness in their families; (b) lower scores on maternal overprotection; and (c) a higher rate of marriage in both ethnic groups and both sexes, except in the case of Jewish men. Religiousness was associated with depression among Jews but not among Protestants. Jewish fathers compared to Protestant fathers were: (a) less strict in the normal group; and (b) less strict, less ‘dominant’ and more ‘inadequate’ in the depressed group. Ethnic links among depressed Jews were probably weaker than those among depressed Protestants.

The findings suggest that: (a) depression among Jews may be related to mental stress arising from ‘marginality’; and (b) single Jewish men may be particularly vulnerable to depression.

A follow-up study was conducted on 146 patients, all the first admissions of one year with the diagnosis of neurosis, admitted as in-patients and day-patients to a hospital giving a general psychiatric early treatment service in Birmingham. Tracing exceeded 97 per cent. Various methods of treatment had been used. Patients were followed up with an interview at their home 12 years after discharge. There were two interviewers, a social worker and a psychiatrist. Assessment at follow-up was on a five-point graded scale in which contributions to the total outcome were made by the social and symptomatic state of the ex-patient.

Twenty-six statistically significant predictive factors were found from the detailed initial information when a graded rating for total outcome at follow-up was compared with presence or absence of the factor. When individual factors were combined, unsatisfactory marital and sexual relationship, poor material management, unsatisfactory social state, and unsatisfactory early environment were predictive of poor outcome. Tests for validity and reliability of the method were carried out.

During the course of research into the reorientating of homosexuals routine EEGs were taken to identify patients with low convulsive threshold to exclude them from treatment (aversion). In an initial series of 28 homosexuals 4 showed EEG abnormalities related to organic conditions, but EEGs of the otherwise apparently normal treatment seeking homosexuals showed more marked overbreathing response than would have been expected by chance.

Five-hundred women electing salpingectomy for contraception and their husbands were studied by means of structured interviews and questionnaires over periods of three months to two years, beginning before surgery. The post-operative follow-up was completed for 374 couples. The subject's condition was compared before and after operation for emergence of any symptoms, and whether there was any significant difference in frequency of intercourse or other sexual behaviour, changes in sexual functioning, emotional adjustment and marital satisfaction. There was evidence of adverse psychological and sexual changes but these were apparently of a mild nature. Eighty-three per cent of the subjects complained of various symptoms, presumably of psychological origin; in 65 per cent sexual desire had declined, and 29 per cent had not resumed intercourse. The mean score of psychiatric symptoms based on clinical ratings rose from 0.38 before to 4.35 after operation, which is statistically highly significant. Paradoxically satisfaction with the operation was expressed by 92 per cent of the subjects.

Plasma prolactin has been estimated in 69 psychiatric in-patients receiving either thioridazine (20–300 mg./day) or chlorpromazine (50–200 mg./day) or other phenothiazines. A homologous radioimmuno-assay was used which depends on an antiserum to human amniotic prolactin. Prolactin levels were significantly increased in these patients compared with control patients, and were dose related. Simultaneous estimation of growth hormone revealed normal levels.

In a recent letter to this Journal, Galdi (1974) stated, ‘Through what is … a genetic approach to classification, Winokur and associates … reported the isolation of two subtypes of unipolar depressive disorder differentiated by age of onset and contrasting family history pattern.’ These subtypes (Winokur, 1974) are termed depression spectrum disease (early-onset; most likely female; familial alcoholism and/or antisocial personality) and pure depressive disease (late onset; equally male or female; little familial alcoholism and/or antisocial personality).

A longitudinal study of a single case of manic-depressive psychosis investigated the relationship between psychiatric ratings, reaction time and two measures of autonomic activity. Measurements were made on 19 occasions over a five-month period. The number of slow responses on the reaction time task increased with increasing depression. Manic periods appeared not to be characterized by a slowing of responses, but rather by an increase in the number of premature responses, i.e. those made to the warning signal. A derived performance index discriminated over the complete range from severe depression to severe mania.

Increased depression was associated with lower heart rate resting levels, and increasing mania with increased skin conductance levels. An increased frequency of slow reaction times was significantly associated with lower resting heart rate. Skin conductance measures correlated significantly with the number of premature responses made on the reaction time tasks. Some differences in the relationships emerged when data obtained during the administration of lithium were included in the analysis.

The results are discussed in relation to both the bipolar and the continuum models of manic-depressive psychosis. The latter model is not supported by the present investigation, since manic episodes were not characterized by a more severe departure from normality than depressive episodes on either the number of slowed responses or autonomic measures.

The relationship between criminality and the outcome of treatment was investigated in opiate addicts attending a drug dependence clinic. A comparison was made between the criminal records of 33 male and 7 female patients who came off drugs and a control group of 29 male and 10 female patients who remained addicted. In male patients, the extent of criminal involvement (as measured by the number of previous convictions on entering treatment) failed to discriminate between those who subsequently achieved abstinence and those who remained addicted. In the small sample of female patients the control group more often had a criminal record and had more previous convictions. These results were in keeping with a previous study of female addicts.

The findings suggest that there is a sex difference in the relationship between criminality and the prognosis for addiction. In male addicts criminal involvement has no significant influence on the outcome of treatment and previous convictions are not a helpful guide to prognosis, whereas in female addicts a criminal record is of more adverse significance.