Studies comparing cases with controls to uncover the causes of psychiatric disorders are common in biological research. The validity of these studies depends upon adherence to the methodological principles underlying the case-control design. However, these principles are often violated. One common practice that violates these principles is the use of well controls. In this paper we describe the bias that it can cause and discuss why the use of well controls leads to invalidity in case-control studies.

Using hypothetical numerical examples we illustrate the consequences of using well controls.

The results illustrate that the use of well controls can cause substantial bias. In no instance does the use of well controls improve validity.

We conclude that the use of well controls is an unhealthy practice in psychiatric research.

The aim of this study was to develop empirically validated criteria for the diagnoses of clinically relevant somatization.

This study was performed in a population-representative cohort consisting of 461 males (47.8%) and 503 females (52.2%), with an average age of 55.8 years (s.d.=11.1). Somatization, anxiety and depression were derived from the Composite International Diagnostic Interview. Mplus was used to perform confirmative factor analyses on the current DSM-IV symptom groups; on alternative symptom clusters previously suggested; and to perform latent class analysis in order to define an empirically derived cut-off for somatization.

The existence of symptom groups as described in DSM-IV was not supported by our data, whereas a differentiation between cardiopulmonary, musculoskeletal, gastrointestinal and general somatic symptoms did fit our data. Latent class analysis revealed two classes characterized by few (n=859) and many (n=105) symptoms. The class of subjects could be approached by a simple cut-off of four functional symptoms (sensitivity 79%, specificity 98%, positive predictive value 82%, negative predictive value 97%) regardless of the number of organ systems involved.

This study in a large population-representative cohort suggests that a simple symptom count can be used as a dimensional diagnosis of somatization. In those instances in which a categorical diagnosis is preferred, a simple cut-off of four out of 43 functional symptoms best fitted our data. We did not find any added value for incorporating the number of symptom clusters into the diagnostic criteria.

DSM-5 may mark the shift from a categorical classification of personality pathology to a dimensional system. Although dimensional and categorical conceptualizations of personality pathology are often viewed as competing, it is possible to develop categories (prototypes) from combinations of dimensions. Robust prototypes could bridge dimensions and categories within a single classification system.

To explore prototype structure and robustness, we used finite mixture modeling to identify empirically derived personality pathology prototypes within a large sample (n=8690) of individuals from four settings (clinical, college, community, and military), assessed using a dimensional measure of normal and abnormal personality traits, the Schedule for Nonadaptive and Adaptive Personality (SNAP). We then examined patterns of convergent and discriminant external validity for prototypes. Finally, we investigated the robustness of the dimensional structure of personality pathology.

The resulting prototypes were meaningful (externally valid) but non-robust (sample dependent). By contrast, factor analysis revealed that the dimensional structures underlying specific traits were highly robust across samples.

We interpret these results as further evidence of the fundamentally dimensional nature of an empirically based classification of personality pathology.

Residual depressive symptomatology constitutes a substantial risk for relapse in depression. Treatment until full remission is achieved is therefore implicated. However, there is a lack of knowledge about the prevalence of (1) residual symptoms in general and (2) the individual residual symptoms in particular.

In a 3-year prospective study of 267 initially depressed primary care patients we established per week the presence/absence of the individual DSM-IV depressive symptoms during subsequent major depressive episodes (MDEs) and episodes of (partial) remission. This was accomplished by means of 12 assessments at 3-monthly intervals with the Composite International Diagnostic Interview (CIDI).

In general, residual depressive symptomatology was substantial, with on average two symptoms present during remissions. Three individual symptoms (cognitive problems, lack of energy and sleeping problems) dominated the course of depression and were present 85–94% of the time during depressive episodes and 39–44% of the time during remissions.

Residual symptoms are prevalent, with some symptoms being present for almost half of the time during periods of remission. Treatment until full remission is achieved is not common practice, yet there is a clear need to do so to prevent relapse. Several treatment suggestions are made.

Genetic and environmental influences on child psychopathology have been studied extensively through twin and adoption designs. We offer a novel methodology to examine genetic and environmental influences on the intergenerational transmission of psychopathology using a sample of parents and children conceived through in vitro fertilization (IVF).

The sample included families with children born through IVF methods, who varied as to whether the child was genetically related or unrelated to the rearing mother and father (mother genetically related, n=434; mother genetically unrelated, n=127; father genetically related, n=403; father genetically unrelated, n=156). Using standardized questionnaires, mothers and fathers respectively reported on their own psychopathology (depression, aggression), their parenting behavior toward their child (warmth, hostility) and their child's psychopathology (depression, aggression). A cross-rater approach was used, where opposite parents reported on child symptoms (i.e. fathers reported on symptoms for the mother–child dyad, and vice versa).

For mother–child dyads, a direct association between mother depression and child depression was observed among genetically unrelated dyads, whereas a fully mediated path was observed among genetically related dyads through mother-to-child hostility and warmth. For father–child dyads, direct and mediated pathways were observed for genetically related father–child dyads. For aggression, the direct association between parent aggression and child aggression was fully mediated by parent-to-child hostility for both groups, indicating the role of parent-to-child hostility as a risk mechanism for transmission.

A differential pattern of genetic and environmental mediation underlying the intergenerational transmission of psychopathology was observed among genetically related and genetically unrelated father–child and mother–child dyads.

Although several studies have reported that repetitive transcranial magnetic stimulation (rTMS) treatment has demonstrable efficacy in patients with depression, the parameters needed to optimize therapeutic efficacy remain unclear. To this end we determined the efficacy of low-frequency right rTMS to the dorsolateral prefrontal cortex (DLPFC) compared to two forms of bilateral rTMS to the DLPFC: (1) sequential low-frequency right-sided followed by high-frequency left-sided rTMS and (2) sequential low-frequency rTMS to both hemispheres.

A total of 219 patients with treatment-resistant depression (TRD) were randomized to a 4-week course of rTMS applied with one of the three treatment conditions. Outcomes were assessed with standard rating scales.

Overall, slightly more than 50% of the patients achieved clinical response criteria. There was no substantial difference in response between the unilateral and bilateral treatment groups. Successful response to rTMS was predicted by a greater degree of baseline depression severity.

There is no substantial difference in efficacy between unilateral right-sided rTMS and the two forms of bilateral rTMS assessed in the study. Furthermore, our results call into question the specificity between frequency and laterality and rTMS response.

The objective of this study was to investigate long-term cognitive and emotional sequelae of mild traumatic brain injury (mTBI), as previous research has remained inconclusive with respect to their prevalence and extent.

Thirty-three individuals who had sustained mTBI on average 6 years prior to the study and 33 healthy control subjects were matched according to age, gender and education. Structural brain damage at time of testing was excluded by magnetic resonance imaging (MRI). A comprehensive neuropsychological test battery was conducted to assess learning, recall, working memory, attention and executive function. Psychiatric symptoms were assessed by the Structured Clinical Interview for DSM-IV Axis I Disorders (SCID-I) and the Beck Depression Inventory (BDI). Possible negative response bias was ruled out by implementing the Word Memory Test (WMT).

The mTBI individuals had significant impairments in all cognitive domains compared to the healthy control subjects. Effect sizes of cognitive deficits were medium to large, and could not be accounted for by self-perceived deficits, depression, compensation claims or negative response bias. BDI scores were significantly higher in the patient group, and three patients fulfilled DSM-IV criteria for a mild episode of major depression.

Primarily, well-recovered individuals who had sustained a minor trauma more than half a decade ago continue to have long-term cognitive and emotional sequelae relevant for everyday social and professional life. mTBI may lead to a lasting disruption of neurofunctional circuits not detectable by standard structural MRI and needs to be taken seriously in clinical and forensic evaluations.

Suicide rates vary widely across nations and ethnic groups. This study aims to explore potential factors contributing to inter-ethnic differences in suicide rates.

Study subjects came from a case-control psychological autopsy study conducted in Taiwan, including 116 consecutive suicides from two aboriginal groups and Taiwanese Han; 113 of them each matched with two living controls. Gender-, age- and method-specific suicide rates, population attributable fraction (PAF) of suicide for five major risk factors, help-seeking before suicide and emergency medical aid after suicide were compared between the three ethnic groups.

One aboriginal group (the Atayal) had significantly higher adjusted rate ratios (RR) of suicide than the other aboriginal group (the Ami) [RR 0.20, 95% confidence intervals (CI) 0.12–0.34] and the Han (RR 0.26, 95% CI 0.16–0.40). Such differences can be explained by higher PAFs of suicide for three major risk factors (substance dependence, PAF 47.6%, 95% CI 25.5–64.2; emotionally unstable personality disorder, PAF 52.7%, 95% CI 32.8–69.0; family history of suicidal behaviour, PAF 43.5%, 95% CI 23.2–60.2) in this group than in the other two groups. This higher suicide rate was substantially reduced from 68.2/100 000 per year to 9.1/100 000 per year, comparable with the other two groups, after stepwise removal of the effects of these three risk factors. Suicide rates by self-poisoning were also significantly higher in this group than in the other two groups.

Higher rates of specific risk factors and use of highly lethal pesticides for suicide contributed to the higher suicide rate in one ethnic group in Taiwan. These findings have implications for developing ethnicity-relevant suicide prevention strategies.

Recent neurodevelopmental models of schizophrenia, together with substantial evidence of neurocognitive dysfunction among people with schizophrenia, have led to a widespread view that general cognitive deficits are a central aspect of schizophrenic pathology. However, the temporal relationships between intellectual functioning and schizophrenia-spectrum illness remain unclear.

Longitudinal data from the Copenhagen High-Risk Project (CHRP) were used to evaluate the importance of intellectual functioning in the prediction of diagnostic and functional outcomes associated with the schizophrenia spectrum. The effect of spectrum illness on intellectual and educational performance was also evaluated. The sample consisted of 311 Danish participants: 99 at low risk, 155 at high risk, and 57 at super-high risk for schizophrenia. Participants were given intellectual [Weschler's Intelligence Scale for Children (WISC)/Weschler's Adult Intelligence Scale (WAIS)] assessments at mean ages of 15 and 24 years, and diagnostic and functional assessments at mean ages 24 and 42 years.

Intellectual functioning was found to have no predictive relationship to later psychosis or spectrum personality, and minimal to no direct relationship to later measures of work/independent living, psychiatric treatment, and overall severity. No decline in intellectual functioning was associated with either psychosis or spectrum personality.

These largely negative findings are discussed in the light of strong predictive relationships existing between genetic risk, diagnosis and functional outcomes. The pattern of predictive relationships suggests that overall cognitive functioning may play less of a role in schizophrenia-spectrum pathology than is widely believed, at least among populations with an evident family history of schizophrenia.

Relatives of schizophrenia patients demonstrate abnormalities in prefrontal cortical activation during executive processing as measured by functional neuroimaging, albeit not consistently. A meta-analysis was conducted to determine whether reliable patterns of brain hypo- and hyperactivity, especially in the middle frontal region, were present in the relatives of patients.

Seventeen studies, containing 18 samples of relatives and controls, were included in this meta-analysis. Studies were included if relatives of schizophrenia patients were compared to controls, an executive processing task was used, and standard space coordinates were reported for the functional activations. Activation likelihood estimation (ALE) was implemented to find convergence across functional neuroimaging experiment coordinates. A separate analysis was conducted to assess the potential impact of a priori hypothesis testing used in region-of-interest (ROI) approaches on the meta-analysis results.

Relatives demonstrated hypo- and hyperactivity in statistically overlapping right middle frontal regions [Brodmann area (BA) 9/10]. Use of an ROI analysis that a priori focused on prefrontal regions resulted in more findings of reduced activity in the middle frontal region.

The cortical regions identified by this meta-analysis could potentially serve as intermediate biological markers in the search for candidate genes for schizophrenia. As neurocognitive deficits are related to functional impairments in patients, a better understanding of neural and genetic vulnerabilities would be beneficial in our efforts to remediate these important deficits.

Cognitive rehabilitation has emerged as an effective treatment for addressing cognitive impairments and functional disability in schizophrenia; however, the degree to which changes in various social and non-social cognitive processes translate into improved functioning during treatment remains unclear. This research sought to identify the neurocognitive and social-cognitive mechanisms of functional improvement during a 2-year trial of cognitive enhancement therapy (CET) for early-course schizophrenia.

Patients in the early course of schizophrenia were randomly assigned to CET (n=31) or an enriched supportive therapy control (n=27) and treated for up to 2 years. A comprehensive neurocognitive assessment battery and the Mayer–Salovey–Caruso Emotional Intelligence Test (MSCEIT) were completed annually, along with measures of functioning. Mediator analyses using mixed-effects growth models were conducted to examine the effects of neurocognitive and social-cognitive improvement on functional change.

Improvements over 2 years in neurocognition and the emotion management branch of the MSCEIT were found to be significantly related to improved functional outcome in early-course schizophrenia patients. Neurocognitive improvement, primarily in executive functioning, and social-cognitive change in emotion management also mediated the robust effects of CET on functioning.

Improvements in neurocognition and social cognition that result from cognitive rehabilitation are both significant mediators of functional improvement in early-course schizophrenia. Cognitive rehabilitation programs for schizophrenia may need to target deficits in both social and non-social cognition to achieve an optimal functional response.

Elevated incidence of psychotic illness has been consistently shown among migrant populations. Ethnic density, the proportion of an ethnic group in a defined area, is cited as one factor with a reduced risk of psychosis where ethnicity is shared. However, UK studies have shown mixed results. We set out to re-examine the ethnic density effect at a greater level of geographic detail than previous studies.

Using a large sample of patient records from general practitioners in South East London, we were able to assess neighbourhood factors at the detailed lower super output area level. This comprises, on average, 1500 people compared with around 6000 per ward, the measure used in previous studies. We compared black (Afro-Caribbean) and white psychosis incidence by neighbourhood ethnic density over a 10-year period.

We found a clear negative association between ethnic density and psychosis incidence. In neighbourhoods where black people comprised more than 25% of the population, there was no longer a statistically significant ethnic difference in psychosis rates. However, where black people were less well represented, their relative risk increased nearly threefold [odds ratio (OR) 2.88, 95% confidence interval (CI) 1.89–4.39]. Furthermore, incidence rates for black people in the lowest density quintiles were over five times greater than in the most dense quintile (OR 5.24, 95% CI 1.95–14.07). However, at ward level this association was much weaker and no longer statistically significant.

Ethnic density is inversely related to psychosis incidence at a detailed local neighbourhood level.

Whether traumatic brain injury (TBI) is an independent risk factor for the subsequent development of schizophrenia has evoked considerable controversy. No evidence has been previously reported from Asia. This study estimated the risk of schizophrenia during a 5-year period following hospital admission for TBI relative to a comparison group of non-TBI patients during the same period in Taiwan.

Two datasets were linked: the Traumatic Brain Injury Registry and the Taiwan National Health Insurance Research Dataset. A total of 3495 patients hospitalized with a diagnosis of TBI from 2001 to 2002 were included, together with 17 475 non-TBI patients as the comparison group, matched on sex, age, and year of TBI hospitalization. Each individual was followed for 5 years to identify any later diagnosis of schizophrenia. Cox proportional hazard regressions were performed for analysis.

During the 5-year follow-up period, patients who had suffered TBI were independently associated with a 1.99-fold (95% confidence interval 1.28–3.08) increased risk of subsequent schizophrenia, after adjusting for monthly income and residential geographical location. The severity and type of TBI was not associated with the subsequent development of schizophrenia.

Our findings add important evidence from Asia and suggest a potential link between TBI and schizophrenia. Our study suggests that clinicians and family members should be alert to possible neuropsychiatric conditions following TBI.

There is a lack of consistent evidence regarding associations of neurological soft signs (NSS) with illness-related variables in schizophrenia. This study examined NSS in first-episode psychotic patients with respect to their factor structure and associations with risk factors, pre-morbid characteristics, psychopathology and spontaneous extrapyramidal syndromes.

First-episode, drug-naive patients with schizophrenia-spectrum disorders (n=177) were assessed for NSS using the Neurological Evaluation Scale, and its 26 constituting items were factor analysed. The identified neurological dimensions were then entered into hierarchical regression models as outcome dependent variables of a set of predictors including risk factors (familial loading for schizophrenia, obstetric complications), pre-morbid characteristics (neurodevelopmental delay, symptoms of attention deficit–hyperactivity disorder, pre-morbid functioning), psychopathological domains (reality distortion, disorganization, negative symptoms, mania, depression, catatonia) and spontaneous extrapyramidal syndromes (parkinsonism, dyskinesia, akathisia).

Five neurological domains were identified: sequencing, release signs, sensory integration, abnormal movements and coordination. Multivariate analyses showed independent associations (p<0.01) of sequencing with familial liability to schizophrenia, deterioration of pre-morbid adjustment and parkinsonism; release signs with obstetric complications, catatonic symptoms and parkinsonism; sensory integration with familial liability to schizophrenia; abnormal movements with familial liability to schizophrenia, obstetric complications, parkinsonism and dyskinesia; and coordination with neurodevelopmental delay. The empirically derived factors explained additional variance over and above that explained by subscale scores across the examined variables.

Familial liability to schizophrenia, obstetric complications, neurodevelopmental delay, deterioration in pre-morbid functioning and observable motor disorders appear to contribute independently to domains of neurological dysfunction. The findings support a neurodevelopmental model of NSS in schizophrenia.

Schizophrenia is a heterogeneous disorder in terms of patient response to antipsychotic treatment. Understanding the heterogeneity of treatment response may help to guide treatment decisions. This study was undertaken to capture inherent patterns of response to antipsychotic treatment in patients with schizophrenia, characterize the subgroups of patients with similar courses of response, and examine illness characteristics at baseline as possible predictors of response.

Growth mixture modeling (GMM) was applied to data from a randomized, double-blind, 12-week study of 628 patients with schizophrenia or schizo-affective disorder treated with risperidone or olanzapine.

Four distinct response trajectories based on Positive and Negative Syndrome Scale (PANSS) total score over 12 weeks were identified: Class 1 (420 patients, 80.6%) with moderate average baseline PANSS total score showing gradual symptom improvement; Class 2 (65 patients, 12.5%) showing rapid symptom improvement; Class 3 (24 patients, 4.6%) with high average baseline PANSS total score showing gradual symptom improvement; and Class 4 (12 patients, 2.3%) showing unsustained symptom improvement. Latent class membership of early responders (ER) and early non-responders (ENR) was determined based on 20% symptom improvement criteria at 2 weeks and ultimate responders (UR) and ultimate non-responders (UNR) based on 40% symptom improvement criteria at 12 weeks. Baseline factors with potential influence on latent class membership were identified.

This study identified four distinct treatment response patterns with predominant representation of responders or non-responders to treatment in these classes. This heterogeneity may represent discrete endophenotypes of response to treatment with different etiologic underpinnings.

Cannabis use is associated with psychosis and a range of subclinical psychiatric symptoms. The strength of this association depends on dosage and age at first use. The current study investigates whether level of cannabis exposure and starting age are associated with specific profiles of subclinical symptoms.

We collected cross-sectional data from a young adult population sample by administering an online version of the Community Assessment of Psychic Experiences (CAPE). Cannabis exposure was quantified as the amount of Euros spent on cannabis per week and the age of initial cannabis use. The primary outcome measure was the odds ratio (OR) to belong to the highest 10% of scores on the total CAPE and the positive-, negative- and depressive symptom dimensions.

In 17 698 adolescents (mean age 21.6, s.d.=4.2 years), cannabis use at age 12 years or younger was strongly associated with a top 10% score on psychotic experiences [OR 3.1, 95% confidence interval (CI) 2.1–4.3] and to a lesser degree with negative symptoms (OR 1.7, 95% CI 1.1–2.5). The OR of heavy users (>€25/week) for negative symptoms was 3.4 (95% CI 2.9–4.1), for psychotic experiences 3.0 (95% CI 2.4–3.6), and for depressive symptoms 2.8 (95% CI 2.3–3.3).

Early start of cannabis use is strongly associated with subclinical psychotic symptoms and to a lesser degree with negative symptoms, while smoking high amounts of cannabis is associated with increased levels of all three symptom dimensions: psychotic, negative and depressive. These results support the hypothesis that the impact of cannabis use is age specific.

Childhood sexual abuse (CSA) has been shown to be a risk factor for personality disorder (PD). However, no previous studies have examined whether associations exist between sexual abuse and abnormal personality as measured both categorically and dimensionally. Such enquiry would more fully illuminate the impact of CSA on adult personality.

Using a large nationally representative sample, we set out to examine associations between CSA and categorically defined PD. We also examined associations between CSA and the five dimensions of personality (openness to experience, conscientiousness, extraversion, agreeableness and neuroticism). A total of 1520 young adults were interviewed to determine the prevalence of sexual abuse occurring before age 16 years. A dimensional measure of personality was completed by 1469 participants, and 1145 had an informant-based PD assessment.

PD was independently associated with repeated CSA [fully adjusted odds ratio (OR) 1.9, 95% confidence interval (CI) 1.1–3.4]. Repeated sexual abuse was also associated with higher neuroticism and lower agreeableness (p values for both <0.001). Adjusting for the effects of potential confounders and mediators, including earlier symptoms of anxiety and depression, had little impact on the strength of associations.

We conclude that repeated CSA is independently associated with categorically defined PD, and also with higher neuroticism and lower agreeableness. Our findings suggest that if a dimensional classification of PDs is adopted in future classification systems, there might be meaningful continuity with previous aetiological research conducted using the current categorical system.

The main aim of this study was to compare a large population of patients with bipolar disorder (BD) types I and II strictly defined as euthymic with healthy controls on measures of decision making. An additional aim was to compare performance on a decision-making task between patients with and without a history of suicide attempt.

Eighty-five euthymic patients with BD-I or BD-II and 34 healthy controls were included. All subjects completed tests to assess verbal memory, attention and executive functions, and a decision-making paradigm (the Iowa Gambling Task, IGT).

Both groups of patients had worse performance than healthy controls on measures of verbal memory, attention and executive function. No significant differences were found between BD-I, BD-II and healthy controls on measures of decision making. By contrast, patients with a history of suicide attempt had lower performance in the IGT than patients without a history of suicide attempt.

Patients with euthymic BD-I and BD-II had intact decision-making abilities, suggesting that this does not represent a reliable trait marker of the disorder. In addition, our results provide further evidence of an association between impairments in decision making and vulnerability to suicidal behavior.