The diversity of research methods applied to psychiatric disorders results in a confusing plethora of causal claims. To help make sense of these claims, the interventionist model (IM) of causality has several attractive features. First, it connects causation with the practical interests of psychiatry, defining causation in terms of ‘what would happen under interventions’, a question of key interest to those of us whose interest is ultimately in intervening to prevent and treat illness. Second, it distinguishes between predictive-correlative and true causal relationships, an essential issue cutting across many areas in psychiatric research. Third, the IM is non-reductive and agnostic to issues of mind–body problem. Fourth, the IM model cleanly separates issues of causation from questions about the underlying mechanism. Clarifying causal influences can usefully structure the search for underlying mechanisms. Fifth, it provides a sorely needed conceptual rigor to multi-level modeling, thereby avoiding a return to uncritical holistic approaches that ‘everything is relevant’ to psychiatric illness. Sixth, the IM provides a clear way to judge both the generality and depth of explanations. In conclusion, the IM can provide a single, clear empirical framework for the evaluation of all causal claims of relevance to psychiatry and presents psychiatry with a method of avoiding the sterile metaphysical arguments about mind and brain which have preoccupied our field but yielded little of practical benefit.

Memory impairment is being recognized increasingly as an important feature of the neuropsychology of schizophrenia. Dysfunction of working memory, a system for the short-term storage and manipulation of information, may relate to a number of core symptoms of schizophrenia. Many studies have examined working memory function in schizophrenia but a clear understanding of the nature and extent of any deficit has been elusive.

A systematic review and meta-analysis of studies comparing working memory function in subjects with schizophrenia and healthy controls was performed. Following a comprehensive literature search, meta-analyses were conducted on 36 measures of phonological, visuospatial and central executive working memory functioning, encompassing 441 separate results from 187 different studies.

Statistically significant effect sizes were found for all working memory measures, indicating deficits in schizophrenia groups. Some of these were robust findings in the absence of evidence of significant heterogeneity or publication bias. Meta-regression analyses showed that the working memory deficit was not simply explained by discrepancies in current IQ between schizophrenia and control groups.

Large deficits in working memory were demonstrated in schizophrenia groups across all three working memory domains. There were, however, no clear differences across subdomains or between particular working memory tasks. There was substantial heterogeneity across results that could only be partly explained.

Impairments in inhibitory function have been found in studies of cognition in schizophrenia. These have been linked to a failure to adequately maintain the task demands in working memory. As response inhibition is known to occur in both voluntary and involuntary processes, an important question is whether both aspects of response inhibition are specifically impaired in people with schizophrenia.

The subjects were 33 patients presenting with a first episode of psychosis (27 with schizophrenia and six with schizo-affective disorder) and 24 healthy controls. We administered two motor response tasks: voluntary response inhibition was indexed by the stop-signal task and involuntary response inhibition by the masked priming task. We also administered neuropsychological measures of IQ and executive function to explore their associations with response inhibition.

Patients with schizophrenia compared to healthy controls showed significantly increased duration of the voluntary response inhibition process, as indexed by the stop-signal reaction time (SSRT). By contrast, there were no group differences on the pattern of priming on the masked priming task, indicative of intact involuntary response inhibition. Neuropsychological measures revealed that voluntary response inhibition is not necessarily dependent on working memory.

These data provide evidence for a specific impairment of voluntary response inhibition in schizophrenia.

Previous research has demonstrated that various types of verbal source memory error are associated with positive symptoms in patients with schizophrenia. Notably, intrusions in free recall have been associated with hallucinations and delusions. We tested the hypothesis that extra-list intrusions, assumed to arise from poor monitoring of internally generated words, are associated with verbal hallucinations and that intra-list intrusions are associated with global hallucination scores.

A sample of 41 patients with schizophrenia was administered four lists of words, followed by free recall. The number of correctly recalled words and the number of extra- and intra-list intrusions were tallied.

The verbal hallucination score was significantly correlated with the number of extra-list intrusions, whereas it was unrelated to the number of correctly recalled words. The number of intra-list intrusions was significantly correlated with the global, but not with the verbal, hallucination score in the subsample of hallucinating patients. It was marginally significantly correlated with the delusion score in delusional patients.

The data corroborate the view that verbal hallucinations are linked to defective monitoring of internal speech, and that errors in context processing are involved in hallucinations and delusions.

Identification of emotional facial expression and emotional prosody (i.e. speech melody) is often impaired in schizophrenia. For facial emotion identification, a recent study suggested that the relative deficit in schizophrenia is enhanced when the presented emotion is easier to recognize. It is unclear whether this effect is specific to face processing or part of a more general emotion recognition deficit.

We used clarity-graded emotional prosodic stimuli without semantic content, and tested 25 in-patients with paranoid schizophrenia, 25 healthy control participants and 25 depressive in-patients on emotional prosody identification. Facial expression identification was used as a control task.

Patients with paranoid schizophrenia performed worse than both control groups in identifying emotional prosody, with no specific deficit in any individual emotion category. This deficit was present in high-clarity but not in low-clarity stimuli. Performance in facial control tasks was also impaired, with identification of emotional facial expression being a better predictor of emotional prosody identification than illness-related factors. Of those, negative symptoms emerged as the best predictor for emotional prosody identification.

This study suggests a general deficit in identifying high-clarity emotional cues. This finding is in line with the hypothesis that schizophrenia is characterized by high noise in internal representations and by increased fluctuations in cerebral networks.

Current psychological models of psychotic symptoms suggest that metacognitive beliefs impact on an individual's appraisal of anomalous experiences, and thereby influence whether these lead to distress and become clinical symptoms. This study examined the relationship between maladaptive metacognitive beliefs, anomalous experiences, anomaly-related distress, anxiety and depression and diagnostic status.

The Metacognitions Questionnaire (MCQ), Symptom Checklist 90 – Revised, and Appraisals of Anomalous Experiences interview were administered to 27 people diagnosed with a psychotic disorder, 32 people meeting At Risk Mental State (ARMS) criteria, 24 people with psychotic-like experiences but no need for care, and 32 healthy volunteers.

The two clinical groups scored higher than non-patient controls and individuals experiencing psychotic-like anomalies with no need for care on most subscales of the MCQ, particularly the ‘general negative beliefs about thoughts’ (NEG) subscale. However, most group differences became non-significant when anxiety and depression were controlled for. Few relationships were found between the MCQ subscales and psychotic-like anomalies and anomaly-related distress. Cognitive/attentional difficulty was the only type of anomaly to be significantly associated with maladaptive metacognitive beliefs. Anomaly-related distress was associated with only the NEG subscale of the MCQ.

Maladaptive metacognitive beliefs, as measured by the MCQ, appear to be related more to elevated levels of general psychopathology in psychotic and at-risk groups than to the presence of, and distress associated with, psychotic experiences. Processes by which metacognitions may impact upon the need for care are discussed.

Epidemiological evidence suggests a link between cannabis use and psychosis. A variety of factors have been proposed to mediate an individual's vulnerability to the harmful effects of the drug, one of which is their psychosis proneness. We hypothesized that highly psychosis-prone individuals would report more marked psychotic experiences under the acute influence of cannabis.

A group of cannabis users (n=140) completed the Psychotomimetic States Inventory (PSI) once while acutely intoxicated and again when free of cannabis. A control group (n=144) completed the PSI on two parallel test days. All participants also completed a drug history and the Schizotypal Personality Questionnaire (SPQ). Highly psychosis-prone individuals from both groups were then compared with individuals scoring low on psychosis proneness by taking those in each group scoring above and below the upper and lower quartiles using norms for the SPQ.

Smoking cannabis in a naturalistic setting reliably induced marked increases in psychotomimetic symptoms. Consistent with predictions, highly psychosis-prone individuals experienced enhanced psychotomimetic states following acute cannabis use.

These findings suggest that an individual's response to acute cannabis and their psychosis-proneness scores are related and both may be markers of vulnerability to the harmful effects of this drug.

This study investigated whether ‘unwanted pregnancy’ (i.e. a negative or ambivalent attitude towards the pregnancy/reproduction) is associated with schizophrenia-spectrum and affective disorders in the offspring in adulthood, and if so, whether other pregnancy, perinatal, childhood or genetic-risk factors account for this association.

In a prospective study beginning during pregnancy, unwanted pregnancy (in combination with other early life risk factors) was studied in relation to adult mental disorders in 75 genetic high-risk (HR) and 91 normal-risk (NR) offspring, defined through maternal psychosis history. Early life risk factors were studied through personal interviews, observations and medical records, and offspring mental disorders were independently diagnosed through follow-up examination at about 22 years of age.

Unwanted pregnancy by itself was significantly related to adult offspring schizophrenia-spectrum disorders in both the total sample and the HR subgroup, but the effect was found to be limited to the HR group and occurred in interaction with genetic risk. Other co-temporaneous pregnancy stressors and later perinatal complications, malformations and early childhood environmental stressors could not explain this relationship. Unwanted pregnancy also interacted with genetic-risk status in relating to affective disorders in the offspring.

Unwanted pregnancy, when occurring together with genetic risk for psychosis, was found to be related to both adult schizophrenia-spectrum and affective mental disorders in the offspring. Although the effect of unwanted pregnancy could be mediated by other yet-unidentified factors, unwanted pregnancy might be a functional, discrete environmental psychosocial factor with its own deleterious impact on offspring mental development, when co-occurring with genetic risk.

There are multiple models of mental illness that inform professional and lay understanding. Few studies have formally investigated psychiatrists' attitudes. We aimed to measure how a group of trainee psychiatrists understand familiar mental illnesses in terms of propositions drawn from different models.

We used a questionnaire study of a sample of trainees from South London and Maudsley National Health Service (NHS) Foundation Trust designed to assess attitudes across eight models of mental illness (e.g. biological, psychodynamic) and four psychiatric disorders. Methods for analysing repeated measures and a principal components analysis (PCA) were used.

No one model was endorsed by all respondents. Model endorsement varied with disorder. Attitudes to schizophrenia were expressed with the greatest conviction across models. Overall, the ‘biological’ model was the most strongly endorsed. The first three components of the PCA (interpreted as dimensions around which psychiatrists, as a group, understand mental illness) accounted for 56% of the variance. Each main component was classified in terms of its distinctive combination of statements from different models: PC1 33% biological versus non-biological; PC2 12% ‘eclectic’ (combining biological, behavioural, cognitive and spiritual models); and PC3 10% psychodynamic versus sociological.

Trainee psychiatrists are most committed to the biological model for schizophrenia, but in general are not exclusively committed to any one model. As a group, they organize their attitudes towards mental illness in terms of a biological/non-biological contrast, an ‘eclectic’ view and a psychodynamic/sociological contrast. Better understanding of how professional group membership influences attitudes may facilitate better multidisciplinary working.

In patients with major depressive disorder (MDD), functional neuroimaging studies have reported an increased activation of the dorsolateral prefrontal cortex (DLPFC) during executive performance and working memory (WM) processing, and also an increased activation of the anterior cingulate cortex (ACC) during baseline conditions. However, the functional coupling of these cortical networks during WM processing is less clear.

In this study, we used a verbal WM paradigm, event-related functional magnetic resonance imaging (fMRI) and multivariate statistical techniques to explore patterns of functional coupling of temporally dissociable dorsolateral prefrontal and cingulate networks. By means of independent component analyses (ICAs), two components of interest were identified that showed either a positive or a negative temporal correlation with the delay period of the cognitive activation task in both healthy controls and MDD patients.

In a prefronto-parietal network, a decreased functional connectivity pattern was identified in depressed patients comprising inferior parietal, superior prefrontal and frontopolar regions. Within this cortical network, MDD patients additionally revealed a pattern of increased functional connectivity in the left DLPFC and the cerebellum compared to healthy controls. In a second, temporally anti-correlated network, healthy controls exhibited higher connectivity in the ACC, the ventrolateral and the superior prefrontal cortex compared to MDD patients.

These results complement and expand previous functional neuroimaging findings by demonstrating a dysconnectivity of dissociable prefrontal and cingulate regions in MDD patients. A disturbance of these dynamic networks is characterized by a simultaneously increased connectivity of the DLPFC during task-induced activation and increased connectivity of the ACC during task-induced deactivation.

Melancholia has long resisted classification, with many of its suggested markers lacking specificity. The imprecision of depressive symptoms, in addition to self-report biases, has limited the capacity of existing measures to delineate melancholic depression as a distinct subtype. Our aim was to develop a self-report measure differentiating melancholic and non-melancholic depression, weighting differentiation by prototypic symptoms and determining its comparative classification success with a severity-based strategy.

Consecutively recruited depressed out-patients (n=228) rated 32 symptoms by prototypic or ‘characteristic’ relevance (using the Q-sort strategy) and severity [using the Severity-based Depression Rating System (SDRS) strategy]. Clinician diagnosis of melancholic/non-melancholic depression was the criterion measure, but two other formal measures of melancholia (Newcastle and DSM-IV criteria) were also tested.

The prevalence of ‘melancholia’ ranged from 20.9% to 54.2% across the subtyping measures. The Q-sort measure had the highest overall correct classification rate in differentiating melancholic and non-melancholic depression (81.6%), with such decisions supported by validation analyses.

In differentiating a melancholic subtype or syndrome, prototypic symptoms should be considered as a potential alternative to severity-based ratings.

Recent evidence suggests that the prevalence of postnatal depression (PND) is highest in low-income developing countries. This study aimed to estimate the prevalence of PND and its associated risk factors among Bangladeshi women.

The study was conducted in the Matlab subdistrict of rural Bangladesh. A cohort of 346 women was followed up from late pregnancy to post-partum. Sociodemographic and other related information on risk factors was collected on structured questionnaires by trained interviewers at 34–35 weeks of pregnancy at the woman's home. A validated local language (Bangla) version of the Edinburgh Postnatal Depression Scale (EPDS-B) was used to measure depression status at 34–35 weeks of pregnancy and at 6–8 weeks after delivery.

The prevalence of PND was 22% [95% confidence interval (CI) 17.7–26.7%] at 6–8 weeks post-partum. After adjustment in a multivariate logistic model, PND could be predicted by history of past mental illness [odds ratio (OR) 5.6, 95% CI 1.1–27.3], depression in current pregnancy (OR 6.0, 95% CI 3.0–12.0), perinatal death (OR 14.1, 95% CI 2.5–78.0), poor relationship with mother-in-law (OR 3.6, 95% CI 1.1–11.8) and either the husband or the wife leaving home after a domestic quarrel (OR 4.0, 95% CI 1.6–10.2).

The high prevalence of PND in the study was similar to other countries in the South Asian region. The study findings highlight the need for programme managers and policy makers to allocate resources and develop strategies to address PND in Bangladesh.

The complex relationships between religiosity, spirituality and the risk of DSM-IV depression are not well understood.

We investigated the independent influence of religious service attendance and two dimensions of spiritual well-being (religious and existential) on the lifetime risk of major depression. Data came from the New England Family Study (NEFS) cohort (n=918, mean age=39 years). Depression according to DSM-IV criteria was ascertained using structured diagnostic interviews. Odds ratios (ORs) for the associations between high, medium and low tertiles of spiritual well-being and for religious service attendance and the lifetime risk of depression were estimated using multiple logistic regression.

Religious service attendance was associated with 30% lower odds of depression. In addition, individuals in the top tertile of existential well-being had a 70% lower odds of depression compared to individuals in the bottom tertile. Contrary to our original hypotheses, however, higher levels of religious well-being were associated with 1.5 times higher odds of depression.

Religious and existential well-being may be differentially associated with likelihood of depression. Given the complex interactions between religiosity and spirituality dimensions in relation to risk of major depression, the reliance on a single domain measure of religiosity or spirituality (e.g. religious service attendance) in research or clinical settings is discouraged.

Evidence suggests that repetitive transcranial magnetic stimulation (rTMS) over the left dorsolateral prefrontal cortex (DLPFC) might be a promising new treatment procedure for depression. However, underlying working mechanisms of this technique are yet unclear. Multiple sessions of rTMS may – apart from the reported antidepressant effects – cause primary improvements in attentional control over emotional information, modulated by changes in cortical brain excitability within stimulated prefrontal regions.

In two experiments, we examined the temporary effects of high-frequency (HF) rTMS (10 Hz) applied over the left and right DLPFC on the attentional processing of emotional information and self-reported mood within samples of healthy volunteers.

The present study showed that one session of HF-rTMS over the right DLPFC produces instant impairments in the ability to inhibit negative information, in line with a characteristic cognitive vulnerability found in depressive pathology, whereas HF-rTMS of the left DLPFC did not lead to significant changes in attentional control. These effects could not be attributed to mood changes.

The findings of the present study may suggest a specific involvement of the right DLPFC in the attentional processing of emotional information.

Studies of patients with anorexia nervosa (AN) have shown that they do not perform well in set-shifting tasks but little is known about the neurobiological correlates of this aspect of executive function. The aim of this study was to measure serum brain-derived neurotrophic factor (BDNF) and to establish whether set-shifting difficulties are present in people with current AN and in those recovered from AN, and whether serum BDNF concentrations are correlated with set-shifting ability.

Serum BDNF concentrations were measured in 29 women with current AN (AN group), 18 women who had recovered from AN (ANRec group) and 28 age-matched healthy controls (HC group). Set-shifting was measured using the Wisconsin Card Sorting Test (WCST). Eating-related psychopathology and depressive, anxiety and obsessive–compulsive symptomatology were evaluated using the Eating Disorder Examination Questionnaire (EDEQ), the Hospital Anxiety and Depression Scale (HADS), and the Maudsley Obsessive–Compulsive Inventory (MOCI) respectively.

Serum BDNF concentrations (mean±s.d.) were significantly lower in the AN group (11.7±4.9 ng/ml) compared to the HC group (15.1±5.5 ng/ml, p=0.04) and also compared to the ANRec group (17.6±4.8 ng/ml, p=0.001). The AN group made significantly more errors (total and perseverative) in the WCST relative to the HC group. There was no significant correlation between serum BDNF concentrations and performance on the WCST.

Serum BDNF may be a biological marker for eating-related psychopathology and of recovery in AN. Longitudinal studies are needed to explore possible associations between serum BDNF concentrations, illness and recovery and neuropsychological traits.

Previous research has found that many patients with anorexia nervosa (AN) are unable to maintain normal weight after weight restoration. The objective of this study was to identify variables that predicted successful weight maintenance among weight-restored AN patients.

Ninety-three patients with AN treated at two sites (Toronto and New York) through in-patient or partial hospitalization achieved a minimally normal weight and were then randomly assigned to receive fluoxetine or placebo along with cognitive behavioral therapy (CBT) for 1 year. Clinical, demographic and psychometric variables were assessed after weight restoration prior to randomization and putative predictors of successful weight maintenance at 6 and 12 months were examined.

The most powerful predictors of weight maintenance at 6 and 12 months following weight restoration were pre-randomization body mass index (BMI) and the rate of weight loss in the first 28 days following randomization. Higher BMI and lower rate of weight loss were associated with greater likelihood of maintaining a normal BMI at 6 and 12 months. An additional predictor of weight maintenance was site; patients in Toronto fared better than those in New York.

This study found that the best predictors of weight maintenance in weight-restored AN patients over 6 and 12 months were the level of weight restoration at the conclusion of acute treatment and the avoidance of weight loss immediately following intensive treatment. These results suggest that outcome might be improved by achieving a higher BMI during structured treatment programs and on preventing weight loss immediately following discharge from such programs.