This issue features groups of papers on genetics, the distributional nature of the milder disorder featuring most prominently in community surveys, diagnostic co-morbidity, neuropsychological and related aspects of schizophrenia.

The first group of papers come from genetic epidemiology, all from twin studies. Agrawal et al. (pp. 1155–1164) examine genetic and environmental origins of detailed aspects of social support. They find evidence for genetic elements in almost all aspects, with some smaller differences between males and females. Wichers et al. (pp. 1165–1174) report effects of pregnancy and birth complications and genetic elements on childhood behaviour problems. They find one specific complication, being of lower birth weight for gestational age, associated with problem behaviour, and an interaction with genetic effects, such that these are weaker in the presence of low birth weight. Johnson et al. (pp. 1175–1185) examine the heritability of depression measured on a symptom scale in Danish twins. They find genetic effects, which do not vary with age over a wide span from 45 to over 95. An accompanying editorial (pp. 1145–1148) looks at the future of genetic epidemiology in a time of accelerating molecular genetic research activity.

Epidemiological surveys frequently measure so-called common mental disorder, psychiatric symptoms in a milder range which may not necessarily fit defined criteria for specific disorders. Melzer et al. (pp. 1195–1201) using this kind of data from a community survey, find a continuous single distribution with no natural cut-off point. Brugha (pp. 1149–1154) in an accompanying editorial discusses the implications of such a dimensional approach and its relation to diagnosis.

In this issue we publish three genetic epidemiology papers (Agrawal et al. 2002; Johnson et al. 2002; Wichers et al. 2002). Psychological Medicine in recent years has had genetic epidemiology as one of its major themes. We also publish some molecular genetic papers. This is a time when the development of molecular genetic technologies, which have already enabled the sequencing of the entire human genome, has been widely and appropriately hailed as a major advance, promising to generate a revolution in the understanding of causes of all human disease, including psychiatric, and in the discovery of new drugs. Psychological Medicine now has a distinguished American Editor from the world of genetic epidemiology in the person of Kenneth Kendler. This editorial, by his British editorial counterpart, is deliberately non-expert, and a view of the psychiatric future of genetic epidemiology from outside the field.

The basic findings for heritability of major psychiatric disorders have become well established and replicated in some decades of research. Family studies were followed by twin studies and adoption studies which established on a much firmer basis that a substantial element in the familiality was genetic. Disappointingly, the genes still remain to be identified with certainty. That is the task of molecular genetics. It is becoming increasingly clear that the task will not be an easy one, because for the most part we seem to have multi-gene disorders, with a number of or many genes of small effect, requiring large samples and quantitative trait methods to elucidate (Plomin et al. 1994).

The well regarded Section of the World Psychiatric Association, on Epidemiology and Public Health, held its biennial meeting at Johns Hopkins University, Baltimore in June 2001. A new feature of the meeting was the ‘work group’, an opportunity to debate topical but unresolved issues. There was standing room only for a discussion on why the differences between self-report and clinician-rated measures of psychopathology matter (Brugha et al. 1999a). This is one of several topics increasingly debated in the context of the seemingly unremitting disparities between epidemiological estimates of the prevalence of psychiatric disorders (Regier et al. 1998). Recent comparisons of clinician and lay (self-report) measures suggest that dichotomous diagnostic categories cannot be measured reliably in large scale community surveys against a clinical standard measure (Brugha, et al. 1999b, 2001; Eaton et al. 2000).

Background. Social support may reduce the risk of psychiatric illness. Though perceived as an environmental measure, genetic factors may influence levels of social support. A relationship between social roles and personality with social support suggests possible sex effects on the sources of individual differences in social support.

Method. We used the responses of MZ and DZ same and opposite sex twins to 16 questions regarding their social life. Six factors – friend support, relative support, friend problem, relative problem, confidants and social integration were used for structural equation modelling. Factor derived scales were analysed for genetic, shared and unique environmental influences. Quantitative and qualitative gender differences were analysed using the software package Mx.

Results. Except for relative support and confidants, no qualitative sex differences were seen. Genetic and individual specific environmental influences accounted for the variance for friend support, friend problems, relative problems and social integration and no quantitative gender differences were seen. For relative support genetic factors were detected in females but not males, while for confidants, the shared environment was important in females but not males.

Conclusions. Except for relative support in males, genetic factors influence variation in all dimensions of social support. Shared environmental factors influence relative support and relative problems in both sexes. Sex differences were detected for confidants and relative support.

Background. Many studies suggest that pregnancy and birth complications (PBCs) are environmental risk factors for child psychopathology. However, it is not known whether the effects of PBCs occur independently of genetic predisposition. The current study examined the possibility of gene–environment interaction in a twin design.

Method. The East Flanders Prospective Twin Survey prospectively records the births of all twin pairs born in East Flanders, Belgium. The current study included 760 twin pairs aged 6–17 years. Multilevel regression analysis was used to assess the effects of several PBCs collected around the time of birth. Using structural equation modelling, ACE models assuming additive genetic (A), shared environmental (C) and unique environmental (E) influences, were compared in order to examine whether the contribution of genetic factors to parent-rated child problem behaviour varied as a function of exposure to dichotomously and continuously defined PBCs.

Results. A main independent effect of lower birth weight, corrected for gestational age (small for gestational age – SGA), on child problem behaviour was found. In addition, there was an interaction between genetic influence and SGA, in that being smaller for gestational age resulted in less influence of additive genetic factors on individual differences in problem behaviour.

Conclusions. Results are suggestive of negative gene–birth weight interaction. Children who are SGA are less sensitive to the genetic effects, and those with high genetic vulnerability are less sensitive to the effects of being SGA in bringing about post-natal mental health effects.

Background. Self-reported depressive symptoms among the elderly have generated considerable interest because they are readily available measures of overall well-being in a population often thought to be at special risk for mental disorder.

Method. The heritability of depression symptoms was investigated in a sample of 2169 pairs of Danish twins (1033 MZ and 1136 same sex DZ) ranging in age from 45 to over 95. Twins completed an interview assessment that identified symptoms of depression, which were scored on Affective, Somatic and Total scales.

Results. Overall heritability estimates (a2) for the Affective (a2 = 0.27, (95% CI 0.22–0.32)). Somatic (a2 = 0.26, (0.21–0.32)), and Total (a2 = 0.29, (0.22–0.34)) scales were all moderate, statistically significant and similar to results from other studies. To assess possible variations in heritability across the wide age span, the sample was stratified into age groups in increments of 10 years. The magnitude of heritable influence did not vary significantly with age or sex. Somatic scale heritability tended to be greater for females than for males, though this difference was not statistically significant. The genetic correlation between the Affective and Somatic scales was 0.71, suggesting substantial common genetic origins.

Conclusions. Though the frequency of self-reported depressive symptoms increased with age in this sample, their heritability did not.

Background. Whereas a number of studies have suggested that parental loss is associated with increased risk for major depression (MD), much less is known about possible gender differences, diagnostic specificity and the time course of the impact of loss.

Method. First-onsets for MD and alcohol dependence (AD) were assessed at personal interviews in 5070 twins from same-sex (SS) and 2118 from opposite-sex (OS) twin pairs ascertained from a population-based registry. Cox Proportional Hazard (PH) and Non-Proportional Hazard (NPH) models, examining first onsets of MD and AD, were used with twins from SS pairs and conditional logistic regression for OS pairs. Parent–child separations prior to age 17 were divided into death and separation from other causes.

Results. The PH assumptions of constant increased risk were rejected for the impact of loss on risk for MD but not for AD. NPH models found significantly increased risk for MD after both death and separation with the risk lasting much longer for separations. For AD, the PH model found significantly increased risk after parental separation but not death. In both SS and OS twin pairs, no sex differences were seen in the impact of parental loss on risk for MD whereas the association between separation and risk for AD was significantly stronger in females than in males.

Conclusion. Consistent sex differences in the association with parental loss were seen for AD but not MD. The analysis of the time-course of increased risk after loss suggests three different patterns which may reflect different relationships: parental death and MD (return to baseline within ∼12 years), separation and MD (return to baseline within ∼30 years) and separation and AD (no change in risk over time).

Background. At the lower end of IQ distributions in general populations, there is a clear excess of cases, representing the distinct pathology of severe learning disability. This study aimed to establish whether such a subpopulation exists in distributions of common mental disorder and depression symptom scores, above epidemiological ‘case’ cut-offs.

Method. Data from 9556 non-psychotic respondents to the 1993 OPCS (Office of Population Censuses and Surveys) National Household Psychiatric Morbidity Survey were analysed. The distribution of total neurotic symptom and depression scores from the revised Clinical Interview Schedule were examined. Automated least squares methods were used to fit the best single statistical distribution to the data.

Results. A single exponential curve provided the best fit for the whole population, but floor effects produced deviations at symptom counts of 0–3. After truncation, exponential distributions fitted excellently. Proportions of the population above conventional cut-offs of [ges ]12 symptoms differed by <12% from expected for a range of low and high prevalence groups. The single exponential model also fitted the depression score.

Conclusions. Symptom counts for the common mental disorders fall within single population distributions, with little apparent numerical excess in the case range. High and low prevalences of these disorders appear to be population characteristics, with shifts in exponential means predicting proportions above case cut-offs.

Background. Exclusion criteria are present in almost all diagnostic categories in both DSM-IV and ICD-10. These exclusion criteria state that one diagnosis is not made if it is ‘due to’ another disorder. However, there is little empirical evidence demonstrating that the hierarchy imposed by the exclusion criteria is meaningful. The current study examines associations between ten common mental disorder pairs to determine whether they are higher for disorder pairs that are classified in DSM-IV and/or ICD-10 as having a hierarchical relationship, than for those that are not hierarchically related.

Method. Data were analysed from the Australian National Survey of Mental Health and Wellbeing, a large (N = 10641) epidemiological survey of mental disorders. Bivariate odds ratios between disorder pairs were calculated from logistic regression analyses. Multivariate odds ratios were also calculated from separate logistic regression analyses in which the sample was restricted to likely positive cases, and co-morbid mental disorders and neuroticism scores were both controlled.

Results. The odds ratios between disorder pairs related according to the exclusion criteria were higher than those of unrelated disorders, for both DSM-IV and ICD-10. When constraints were placed on the data to control for the effects of co-morbid disorders and neuroticism the same pattern was evident in DSM-IV, but not in ICD-10.

Conclusion. The patterns of association between disorder pairs found in the exclusion criteria for DSM-IV appear to more closely mirror the patterns of association found in epidemiological data. While this does not guarantee that the exclusion criteria are valid it is argued that identifying significant associations should be the first step in establishing meaningful exclusion criteria.

Background. Although it is well known that generalized anxiety disorder (GAD) is highly co-morbid with other mental disorders, little is known about the extent to which earlier disorders predict the subsequent first onset and persistence of GAD. These associations are examined in the current report using data from four community surveys in the World Health Organization (WHO) International Consortium in Psychiatric Epidemiology (ICPE).

Method. The surveys come from Brazil, Canada, the Netherlands and the United States. The Composite International Diagnostic Interview (CIDI) was used to assess DSM-III-R anxiety, mood and substance use disorders in these surveys. Discrete-time survival analysis was used to examine the associations of retrospectively reported earlier disorders with first onset of GAD. Logistic regression analysis was used to examine the associations of the disorders with persistence of GAD.

Results. Six disorders predict first onset of GAD in all four surveys: agoraphobia, panic disorder, simple phobia, dysthymia, major depression and mania. With the exception of simple phobia, only respondents with active disorders have elevated risk of GAD. In the case of simple phobia, in comparison, respondents with a history of remitted disorder also have consistently elevated risk of GAD. Simple phobia is also the only disorder that predicts the persistence of GAD.

Conclusions. The causal processes linking temporally primary disorders to onset of GAD are likely to be state-dependent. History of simple phobia might be a GAD risk marker. Further research is needed to explore the mechanisms involved in the relationship between simple phobia and subsequent GAD.

Background. This article presents epidemiological data on the prevalence of DSM-IV generalized anxiety disorder (GAD) and sub-threshold GAD (fulfilling three out of four GAD criteria) in young women together with data on co-morbidity and psychosocial functioning. The prevalence of clinically relevant worry and its predictive validity for the diagnosis of GAD were also examined.

Method. Young women (N = 2064), aged between 18 and 25, from a representative German community sample were diagnosed with a structured clinical interview (ADIS-L, German research version). An additional interview questioned all the participants about the frequency/intensity and uncontrollability of diverse worry topics.

Results. Thirty-seven participants (1.8%) fulfilled the criteria of current GAD (1 week point prevalence) and 56 received a lifetime diagnosis (2.7%); a further 50 participants (2.3%) were diagnosed with sub-threshold GAD. Co-morbidity between GAD and other disorders was high for current (68%) and lifetime GAD (91%). GAD, as well as sub-threshold GAD, showed clearly reduced levels of psychosocial functioning. Whereas worries of low intensity and high controllability were ubiquitous in all subsamples, clinically defined worrying was rarely present in healthy subjects (0.89%) and of adequate predictive accuracy for GAD.

Conclusions. Full GAD and sub-threshold GAD were moderately frequent in young women. Although DSM-IV worry criteria proved to be highly useful, the strictness of the complete GAD-criteria should not lead to absence of attention from subclinical generalized anxiety states in research and practice.

Background. Childhood adversity places individuals with major depression at risk for anxiety and dysthymia co-morbidity. The goal of the present paper is to broaden this area of research by examining specificity between the type of adversity (e.g. abuse versus neglect/indifference) and the resulting co-morbid disorder (e.g. anxiety versus dysthymia co-morbidity).

Method. The volunteer sample consisted of 76 women meeting Diagnostic and Statistical Manual (DSM-IV) criteria for major depression. Of these, 28 were diagnosed with a co-morbid anxiety disorder and 21 were diagnosed with co-morbid dysthymia. Childhood physical abuse, sexual abuse, psychological abuse, antipathy and indifference were assessed using a contextual interview and rating system.

Results. Severe sexual abuse and psychological abuse were significantly and preferentially associated with co-morbid anxiety, while severe physical abuse was significantly and preferentially associated with co-morbid dysthymia. Indifference and antipathy were significantly associated with both co-morbid anxiety and dysthymia. Multivariate analyses revealed that severe sexual abuse was the adverse childhood experience most strongly associated with co-morbid anxiety.

Conclusions. These results suggest that particular adverse experiences in childhood do set up specific vulnerabilities to the expression of anxiety versus dysthymia co-morbidity in adulthood major depression. Cognitive mediators of these associations are discussed as avenues of future research.

Background. It has been argued recently that the attentional dysfunction in schizophrenia occurs as a result of an inability to inhibit automatic attentional shifts to compelling external stimuli. However, this hypothesis is based on performance on paradigms that require overt or covert shifts of spatial attention.

Method. We investigated responses to foveally presented stimuli in patients with schizophrenia and healthy controls as they performed unidimensional and bidimensional versions of the flanker task. In both tasks, centrally presented target stimuli were flanked by peripheral stimuli that were either congruent or incongruent with the behavioural goal of the subject. In the bidimensional task, the flanking stimuli could be congruent and incongruent on multiple stimulus characteristics.

Results. On the unidimensional flanker task, the behavioural goal modulated the responses of the schizophrenia group such that response times (RTs) to target stimuli that were flanked by congruent stimuli were faster than RTs to target stimuli flanked by incongruent stimuli. However, on the bidimensional flanker task, the responses of schizophrenia patients were no longer constrained by the behavioural goal and RTs to both congruent and incongruent stimuli were equivalent.

Conclusions. It appears that the attentional dysfunction in schizophrenia may reflect difficulty in resolving multiple and simultaneous response conflicts. These findings suggest a possible role for the anterior cingulate cortex in the attentional impairments associated with schizophrenia.

Background. In schizophrenia, impaired conscious retrieval of past events and facts may represent a selective cognitive deficit of declarative memory against a background of a generalized neuropsychological impairment. We aimed to disentangle the neural subprocesses leading to this deficit applying the ‘Remember/Know procedure’.

Method. Event-related potentials (ERPs) were recorded as 14 schizophrenic patients and 14 controls recognized an equal mixture of previously presented old and new words. For recognized old words, participants were required to judge whether recognition was associated with recollection (‘Remember’) or familiarity (‘Know’), either reflecting episodic or semantic memory.

Results. Patients showed a lack of ‘Remember responses’, which led to more opportunities to make ‘Know responses’. ERPs for ‘Remember’ compared to ‘New responses’ differed consistently in controls over left temporo-parietal and right frontal electrode sites. Although schizophrenic patients showed the same topography for this Remember old/new effect, it was apparent over temporo-parietal sites for only 800 ms and over right frontal sites for 1100 ms post-stimulus. For controls, the Know old/new effect was elicited over temporo-parietal sites between 500 and 800 ms. For patients, it showed a widespread maximum over frontal sites between 500 and 1100 ms.

Conclusions. The shorter time course of the left temporo-parietal Remember old/new effect suggests that the patients' episodic memory impairment was possibly mediated by a dysfunction of the mediotemporal regions. The more widespread frontal Know old/new effect in the patients suggests that the prefrontly mediated processes associated with retrieval of semantic memory may be enhanced compensatorily.

Background. Disturbed speech in schizophrenia may reflect pragmatic deficits of expressive language. Pragmatic comprehension deficits also occur in schizophrenia. This study investigated whether poor ‘mind-reading’ (i.e. a general difficulty with inferring and monitoring other people's thoughts) causes pragmatic language impairments of both expression and comprehension in patients with schizophrenia.

Method. Mind-reading (or theory of mind) was tested in patients with schizophrenia and in healthy controls using a false-belief picture-sequencing task. Pragmatic comprehension skills were assessed using a test of non-literal speech interpretation. Clinical ratings of formal thought disorder (FTD) indexed the expressive language deficits of patients. To control for possible contributory effects of executive dysfunction, inhibitory control was tested using capture picture-sequences and executive-planning was tested using the Tower of London task.

Results. False-belief picture-sequencing, understanding of irony and understanding of metaphors were all selectively impaired in the patients. Poor mind-reading (indexed by high error rate in sequencing false-belief stories) was associated with poor understanding of irony, but was unrelated to poor understanding of metaphors. Whereas poor appreciation of irony and poor mind-reading were associated with high ratings of positive formal thought disorder, high ratings of negative formal thought disorder were associated with poor understanding of metaphors and executive dysfunction.

Conclusions. Whereas poor mind-reading may contribute to positive aspects of formal thought disorder and impaired appreciation of irony in patients with schizophrenia; negative features of formal thought disorder and poor understanding of metaphors appear better explained by abnormal semantics. Overall, the findings of this study support the view that the functional basis of formal thought disorder in schizophrenia is not unitary.

Background. It has been suggested that the increased incidence of psychosis in African-Caribbeans living in England may be due to illnesses in which social stress plays an important aetiological role. If this is the case, the prevalence of factors associated with psychosis that predate illness onset such as obstetric complications, pre-morbid neurological illness and poor childhood social adjustment may be expected to be lower in African-Caribbean than Whites psychotic patients.

Method. Details of obstetric complications, pre-morbid neurological illness, and pre-morbid social adjustment were obtained for 337 psychotic patients by patient interview, interviews of mothers and chart review. The proportions of patients with each ‘risk factor’ in the African-Caribbean (N = 103) and White (N = 184) groups were compared using regression analysis; age, sex, social class, diagnosis and referral status were possible explanatory variables.

Results. African-Caribbean patients were less likely to have suffered a pre-morbid neurological disorder than their White counterparts (odds ratio 0.19, 95% CI 0.06–0.61). There was no significant difference in pre-morbid social adjustment or obstetric complications between the two groups, though fewer obstetric complications were reported in the African-Caribbean group (21.5%) than the White group (30.9%).

Conclusions. African-Caribbean patients with psychosis have experienced less pre-morbid neurological illness.

Objective. To determine the relationship between self-perceived health and suicidal ideation among patients in general internal medicine practice settings.

Method. A representative sample of 4007 patients was assessed for current suicidal ideation, self-perception of health, current medical disorders and current mental disorders (major depression, generalized anxiety disorder, panic attacks and alcohol use disorder) with the PRIME-MD Patient Health Questionnaire.

Results. Patients with self-perception of poor health, compared with those who reported more favourable health perception, were significantly more likely to report current suicidal ideation (35.2% v. 8.3%; χ2 = 97.4, df = 1, P<0.0001). Multivariate logistic regression analyses revealed that the perception of poor health was associated with a significantly increased risk of suicidal ideation (OR = 3.1, CI 1.9, 5.0), even after adjusting for sociodemographic characteristics, mental disorders and common physical illnesses.

Conclusion. Self-perception of poor health is associated with a significantly increased risk of suicidal ideation among general medical patients, even in the absence of common mental and physical disorders. These findings add to a growing literature on the importance of self-perceived health in the treatment and outcomes of mental and physical well-being by documenting self-perceived poor health as a risk factor for suicidal ideation in medical patients.

Background. Several studies have investigated the issue of the natural course of schizophrenia. Our study addressed whether there is evidence for progression, potentially deteriorating, over the long-term course of the disorder.

Method. Modern survival analysis techniques were applied to case-register data on the pattern of readmission to in-patient psychiatric facilities. The sample consisted of a total of 8953 persons with schizophrenia.

Results. No evidence of a progressive course of schizophrenia was found in the present study. The accelerating pattern of the course of schizophrenia described by some authors, including a previous analysis of an almost identical dataset, can be explained by selection.

Conclusions. Heterogeneity reflecting the various levels of individual vulnerability may govern the overall individual course of schizophrenia. We hypothesize that the persistent deficit syndrome and negative symptoms are influential determinants of this heterogeneity.

Background. We aimed to evaluate the diagnostic accuracy of a highly structured diagnostic interview in relation to a semi-structured diagnostic procedure. We compared the World Health Organization Composite International Diagnostic Interview Short Form (CIDI-SF) in diagnosing major depressive episode (MDE) to consensus diagnoses based on the SCAN interview (Schedules for Clinical Assessment in Neuropsychiatry).

Method. Subjects comprised a follow-up sample of 239 20–24-year-old former high-school students who were administered the SCAN and immediately thereafter the CIDI-SF. Concordance was estimated for 12-month MDE, using different cut-points of the CIDI-SF and for any affective disorders.

Results. Correspondence between instruments was moderate for MDE (κ = 0.43, sensitivity 0.71, specificity 0.82), but better for any affective disorder (κ = 0.60, sensitivity 0.70, specificity 0.90). Most false negatives suffered from their depression as much as those correctly identified by the CIDI-SF. False negativity was mainly due to not endorsing the stem questions of the CIDI-SF. Of the false positives almost half had an affective disorder other than MDE.

Conclusions. The CIDI-SF seems to function best in identifying a broader category of affective disorders. It could be useful in large-scale community surveys where more extensive psychiatric interviews are not feasible.

Background. A randomized controlled trial of problem-solving treatment, antidepressant medication and the combination of the two treatments found no difference in treatment efficacy for major depressive disorders in primary care. In addition to treatment outcome, the trial sought to determine possible mechanisms of action of the problem-solving intervention.

Method. Two potential mechanisms of action of problem-solving treatment were evaluated by comparison with drug treatment. First, did problem-solving treatment work by achieving problem resolution and secondly, did problem-solving treatment work by increasing the patients' sense of mastery and self-control?

Results. Problem-solving treatment did not achieve a greater resolution in the patients' perception of their problem severity by comparison with drug treatment, neither did problem-solving treatment result in a greater sense of mastery or self-control.

Conclusions. The results from this study did not support the hypotheses that for patients with major depression, by comparison with antidepressant medication: problem-solving treatment would result in better problem resolution; or that problem-solving treatment would increase the patients' sense of mastery and self-control.