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Altered neurocognitive function in schizophrenia could reflect both genetic and illness-specific effects.
To use functional magnetic resonance imaging to discriminate between the influences of the genetic risk for schizophrenia and environmental factors on the neural substrate of verbal fluency, a candidate schizophrenia endophenotype using a case control twin design.
We studied 23 monozygotic twin pairs: 13 pairs discordant for schizophrenia and 10 pairs of healthy volunteer twins. Groups were matched for age, gender, handedness, level of education, parental socio-economic status, and ethnicity. Behavioural performance and regional brain activation during a phonological verbal fluency task were assessed.
Relative to healthy control twins, both patients and their non-psychotic co-twins produced fewer correct responses and showed less activation in the medial temporal region and inferior frontal gyrus. Twins with schizophrenia showed greater activation than both their non-psychotic co-twins and controls in right lateral temporal cortex, reflecting reduced deactivation during word generation while their non-psychotic co-twins showed greater activation in the left temporal cortex.
Both genetic vulnerability to schizophrenia and schizophrenia were associated with impaired verbal fluency performance, reduced engagement of the medial temporal region and dorsal inferior frontal gyrus. Schizophrenia was specifically associated with an additional reduction in deactivation in the right temporal cortex.
Recent studies have identified DAAO as a probable susceptibility gene for schizophrenia and bipolar disorder. However, little is known about how this gene may affect brain function to increase vulnerability to these disorders.
The present investigation examined the impact of DAAO genotype on brain function in patients with schizophrenia, patients with bipolar I disorder and healthy volunteers.
We tested the hypotheses that the high-risk variant of DAAO would be associated with altered prefrontal function and functional connectivity in schizophrenic and bipolar patients.
We used functional magnetic resonance imaging to measure brain responses during a verbal fluency task in a total of 121 subjects comprising 40 patients with schizophrenia, 33 patients with bipolar I disorder and 48 healthy volunteers. We then used statistical parametric mapping (SPM) and psycho-physiological interaction (PPI) analyses to estimate the main effects of diagnostic group, the main effect of genotype and their interaction on brain activation and functional connectivity.
In schizophrenic patients relative to bipolar patients and controls, the high-risk variant of DAAO was associated with lower deactivation in the left precuneus and greater activation in the right calcarine and posterior cingulate gyrus during task performance. In addiction, these areas expressed altered functional connectivity with the rest of the brain in schizophrenic patients relative to bipolar patients and controls.
Our results suggest that genetic variation in DAAO has a significant impact on brain function and provide preliminary evidence for a disease-specific pattern of gene action in specific brain regions.
Epidemiological studies have reported that the increased risk of developing psychosis in cannabis users is dose related. In addition, experimental research has shown that the active constituent of cannabis responsible for its psychotogenic effect is Delta-9-Tetrahydrocannabinol (THC) (Murray et al, 2007). Recent evidence has suggested an increased in potency (% TCH) in the cannabis seized in the UK (Potter et al, 2007).
We predicted that first episode psychosis patients are more likely to use higher potency cannabis and more frequently than controls.
We collected information concerning socio-demographic, clinical characteristics and cannabis use (age at first use, frequency, length of use, type of cannabis used) from a sample of 191 first-episode psychosis patients and 120 matched healthy volunteers. All were recruited as part of the Genetic and Psychosis (GAP) study which studied all patients who presented to the South London and Maudsley Trust.
There was no significant difference in the life-time prevalence of cannabis use or age at first use between cases and controls. However, cases were more likely to be regular users (p=0.05), to be current users (p=0.04) and to have smoked cannabis for longer (p=0.01). Among cannabis users, 86.8% of 1st Episode Psychosis Patients preferentially used Skunk/Sinsemilla compared to 27.7% of Controls. Only 13.2 % of 1st Episode psychosis Patients chose to use Resin/Hash compared to 76.3% of controls. The concentration of TCH in these in South East London, ranges between 8.5 and 14 % (Potter et al, 2007). Controls (47%) were more likely to use Hash (Resin) whose average TCH concentration is 3.4% (Potter et al, 2007).
Patients with first episode psychosis have smoked higher potency cannabis, for longer and with greater frequency, than healthy controls.
To examine the effect of a polymorphism in the Dopamine Transporter (DAT) gene on brain activation during executive function and, for the first time:
1. determine the extent to which this is altered in schizophrenia and
2. use a verbal fluency paradigm.
This is relevant since:
1. DAT plays a key role in the regulation of dopamine, which modulates cortical activation during cognitive tasks and
2. a disruption of dopamine function is a fundamental pathophysiological feature of schizophrenia.
Functional magnetic resonance imaging was used to measure whole-brain responses during overt verbal fluency in 85 subjects: 44 healthy volunteers and 41 DSM-IV schizophrenia patients. Main effects of genotype and diagnostic group on activation and their interaction were estimated using an ANOVA in SPM5.
The 10-repeat allele of the 3'UTR VNTR was associated with greater activation than the 9-repeat allele in the left (Z=4.8; FWEp=0.005) and right (Z=4.2; FWEp=0.057) anterior insula and with decreased activation in the rostral anterior cingulate (Z=4.3 FWEp=0.04) during word generation (versus baseline). These effects were irrespective of diagnostic group but generally more marked in patients. There were also strong trends for groupxgenotype interactions in the left middle frontal gyrus and the left nucleus accumbens. Analysis was controlled for task performance, IQ, antipsychotic medication, psychopathology and demographics.
Cortical function during executive tasks is normally modulated by variation in the DAT gene, effect which is dependent on the brain region. DAT's effect may be altered in schizophrenia patients, which may reflect altered central dopamine function.
Neurocognitive and functional neuroimaging studies point to frontal lobe abnormalities in schizophrenia. Molecular and behavioural genetic studies suggest that the frontal lobe is under significant genetic influence. We carried out structural magnetic resonance imaging (MRI) of the frontal lobe in monozygotic (MZ) twins concordant or discordant for schizophrenia and healthy MZ control twins.
The sample comprised 21 concordant pairs, 17 discordant affected and 18 discordant unaffected twins from 19 discordant pairs, and 27 control pairs. Groups were matched on sociodemographic variables. Patient groups (concordant, discordant affected) did not differ on clinical variables. Volumes of superior, middle, inferior and orbital frontal gyri were calculated using the Cavalieri principle on the basis of manual tracing of anatomic boundaries. Group differences were investigated covarying for whole-brain volume, gender and age.
Results for superior frontal gyrus showed that twins with schizophrenia (i.e. concordant twins and discordant affected twins) had reduced volume compared to twins without schizophrenia (i.e. discordant unaffected and control twins), indicating an effect of illness. For middle and orbital frontal gyrus, concordant (but not discordant affected) twins differed from non-schizophrenic twins. There were no group differences in inferior frontal gyrus volume.
These findings suggest that volume reductions in the superior frontal gyrus are associated with a diagnosis of schizophrenia (in the presence or absence of a co-twin with schizophrenia). On the other hand, volume reductions in middle and orbital frontal gyri are seen only in concordant pairs, perhaps reflecting the increased genetic vulnerability in this group.
The heritability of the brain’s structure and function in schizophrenia remains elusive
To assess the influence of genetic and environmental factors on executive function in schizophrenia.
A twin-sibling study of 206 subjects; 163 twins, varying in their zygosity and concordance for schizophrenia, and 43 singletons from sibling clusters varying in their concordance for schizophrenia. We assessed performance and regional brain activation using functional magnetic resonance imaging, during a phonological verbal fluency task.
Patients and their unaffected relatives developed greater activation in the left inferior frontal gyrus, and greater deactivation in the middle temporal gyri bilaterally. These features were maximally evident in subjects with schizophrenia. When the analysis was restricted to the unaffected relatives and healthy controls, a similar pattern was evident. Heritability was greatest in the left hippocampus and the right middle temporal gyrus. Genetic modelling indicated a phenotypic correlation between schizophrenia and increased activity in the inferior frontal gyrus and reduced activity in the left middle temporal gyrus and left hippocampus, which appeared principally due to shared genetic effects.
Both schizophrenia and its familial vulnerability were associated with altered frontal, parahippocampal and temporal activation during verbal fluency. The altered left inferior frontal activity was particularly associated with schizophrenia, while altered left medial temporal and right middle temporal activity were more heritable. The latter was more intimately linked to the genetic risk for schizophrenia, and thus the better candidate intermediate phenotype.
Recent studies have shown that cannabis use acts as a specific risk factor provoking the onset of psychosis in vulnerable individuals. Association of adolescent cannabis use and psychosis risk was studied after adjustment with prodromal symptoms.
To assess possible causality between cannabis use and the risk of psychosis.
To examine associations between cannabis use and the risk of psychosis in 10 years follow-up while taking into account the prodromal symptoms of psychosis in a prospective general population sample.
The sample (N=6258) composed of a prospective Northern Finland Birth Cohort 1986. Questionnaire on prodromal symptoms for psychosis (PROD-screen) and on drug use was conducted when the cohort members were 15-16 years old. The participants were asked if they had tried cannabis: never, once, 2-4 times, 5 times or more. Information on psychoses was gathered from registers until age 27 years.
In total 102 new psychoses emerged. The proportion of psychoses in the groups 'never”, 'once”, '2-4 times”, '5 times or more” were 1.5%, 2.8%, 3.6%, and 8.5%, respectively. The hazard ratio (HR) for risk of psychosis in subjects who had tried cannabis 5 times or more was 5.9 (95% CI 2.4-14.4) when compared to non-users. The association remained statistically significant when adjusted for prodromal symptoms and parental psychosis (HR 2.6, 1.0-6.6). When gender and smoking was taken into account association was no longer significant (HR 2.3, 0.9-6.0).
Adolescent cannabis use associates with increased risk of first-episode psychosis even after controlling for baseline prodromal symptoms.
Social withdrawal is among the first signs of the prodromal state of psychosis seen in clinical samples. The aim of this prospective study was to find out whether difficulty in making contact with others and social withdrawal precede first episode psychosis in the young general population.
The members of the Northern Finland Birth Cohort 1986 (n = 6274) completed the PROD-screen questionnaire in 2001–2002. The Finnish Hospital Discharge Register was used to detect both new psychotic and non-psychotic disorders requiring hospitalisation during 2003–2008.
Twenty-three subjects developed psychosis and 89 developed a non-psychotic mental disorder requiring hospitalisation during the follow-up. Of those who developed psychosis, 35% had reported difficulty or uncertainty in making contact with others and 30% social withdrawal in adolescence. In hospitalised non-psychotic disorder, the corresponding precentages were 10 and 13% and in the control group without hospital-treated mental disorder 9 and 11%. The differences between psychotic and non-psychotic hospitalised subjects (P < 0.01) as well as controls (P < 0.001) were statistically significant regarding difficulty or uncertainty in making contact with others.
In this general population-based sample self-reported difficulty or uncertainty in making contact with others in adolescence preceded psychosis specifically compared to hospitalised non-psychotic mental disorders and controls.
Schizophrenia is an aetiologically complex disorder associated with significant familial risk. It is marked also by reductions in whole brain, grey and possibly white matter volumes. How these pathological abnormalities are influenced by schizophrenia's genetic and environmental risk remains uncertain.
We investigated the relationship between familial and environmental risk on brain volume in twin pairs varying in their zygosity and concordance for schizophrenia, and healthy control twins, using a variety of complementary imaging strategies. These included region of interest and automated tissue segmentation volumes and voxel based morphometry.
We found that whole brain, grey, white, frontal and right hippocampal volumes were smaller in probands with schizophrenia compared to healthy controls. Well co-twins from MZ discordant pairs showed a trend towards lower white matter volume compared to the healthy controls. Well co-twins from DZ discordant pairs had smaller hippocampal volumes compared to the healthy controls. The patients with schizophrenia and their well co-twins from MZ discordant pairs differed in the superior frontal cortex using both region of interest and VBM techniques. Lower birth weight and hypoxia were both associated with lower whole brain volumes, and with lower white and grey matter volumes respectively.
Our data suggest that total brain and grey matter volume reductions in schizophrenia, possibly focused in part in the frontal cortex, are related primarily to unique environmental factors, including perinatal complications. The white matter and local hippocampal volume reductions suggest an additional vulnerability to genetic risk effects.
High potency cannabis has been associated with greater risk, and earlier onset of psychosis. However, its effect on brain structure, particularly white matter (WM), has never been explored.
Objectives and Aims
To elucidate the interplay between cannabis potency, pattern of use (frequency and age of first use) and CC microstructure; in patients with first-episode psychosis (FEP) and healthy controls.
56 FEP and 43 healthy controls underwent Diffusion-Tensor Imaging combined with WM mapping-tractography. CC was virtually dissected and segmented to calculate Fractional Anisotropy (FA), Mean Diffusivity (MD), Axial Diffusivity (AD) and Radial Diffusivity (RD) for each CC segment.
High potency cannabis users had higher Total CC MD and Total CC AD than both low potency users and those who never used (p=0.009 and p=0.02 respectively). Daily users also had higher Total CC MD and Total CC AD than both occasional users and those who never used (p=0.02 and p=0.01 respectively). Furthermore, daily/highpotency users had higher Total CC MD than those who never used or used weekly [F(2,57)=4.7, p=0.01]. There was no effect of diagnosis or diagnosis X potency/patterns of use interactions; neither differences between users who started before the age of 15 and those who started later were detected, in any diffusivity measures.
Frequent use of high-potency cannabis significantly affects callosal microstructure, regardless of the presence of a psychotic disorder. Given the increased availability and use of high potency preparations in Europe, raising awareness about some of their detrimental effects is an important avenue to pursue.
The impact of cannabis use on brain structure, particularly white matter (WM), is poorly understood. The CC is the largest WM structure in the brain. Abnormalities revealed in the CC may underlie functional anomalies of cannabis use. This is the largest study to explore the effect of cannabis on callosal WM connectivity among first episode psychosis (FEP) and controls.
To investigate the relationship between cannabis use and WM micro-structural integrity of the CC, in FEP and healthy controls.
We evaluated 56 FEP patients (67% current cannabis users), and 43 healthy controls (44% current cannabis users). We used Diffusion Tensor Imaging combined with a WM mapping-tractography technique to investigate the microstructural integrity of the CC.
Total CC Fractional anisotropy (FA) was lower in patients than controls (p=0.05). Cannabis-using patients had lower FA of the total CC than cannabis-using controls (p=0.04). There were no differences in FA between cannabis-using patients and those who had never used. However, cannabis-using patients had higher mean diffusivity (MD) of total CC (p= 0.02), Rostral-Body (p=0.003), Anterior Mid-Body (p=0.03) and the Splenium (p=0.06) than patients who never used cannabis. There were no differences in MD between patient users who started before the age of 16 and those who started later.
Cannabis is associated with a significant effect on callosal WM integrity only in patients with psychosis. Disturbed callosal connectivity may explain some of the abnormalities with regard to the functional and clinical outcomes in FEP cannabis users, including measures of cognitive impairment.
There are limited amount of studies comparing time trends of incidence and risk factors of psychosis.
To compare time trends of incidence of psychosis in two population samples.
To study 1) onset age and cumulative incidence of psychoses in two Northern Finland Birth Cohorts (NFBC), 2) changes in type of diagnosis and risk factors.
The NFBC 1966 (N=12,058) and NFBC 1986 (N=9,432) are prospective cohorts of the two provinces of Finland with the live born children followed since pregnancy. The data for psychosis and risk factors were collected from variety of nationwide registers and earlier collected data of the NFBCs. The follow-up time was in both cohorts in average 26.5 years.
Proportion of all psychoses was higher in NFBC 1986 than in the NFBC 1966 (1.81% vs 1.0%). There were more affective psychoses in NFBC 1986 (0.5% vs 0.1%), but incidence of schizophrenia was the same (0.4%) in both cohorts. The age of onset was lower in NFBC 1986 than in NFBC 1966 and majority of this cases were females. Only parental psychosis was a significant risk factor predicting psychosis (Hazard Ratios >3.0) in both cohorts.
In conclusion, two birth cohorts within 20 years covering altogether about 40 years showed changes in terms of incidence, age of onset, and type of psychosis.
The effects of long-term antipsychotic medication use on structural brain changes in psychoses are still unknown. Severity and duration of illness are key confounders when evaluating antipsychotic effects on brain morphology.
Understanding the role of antipsychotic medication on brain morphology in psychoses.
To analyze whether cumulative lifetime or current antipsychotic medication dose relates to brain morphology in schizophrenia and other psychoses at age of 43 years.
Forty-four schizophrenia cases and 35 with other psychoses from the Northern Finland Birth Cohort 1966 were scanned on a 1.5T GE Signa scanner and brain structures were extracted using volBrain automated volumetry system (http://volbrain.upv.es). Data of antipsychotic medication were collected from medical records and interviews. We used linear regression model to analyze the effect of antipsychotic medication on brain volumes and used intracranial volume and onset age as covariates. We also performed additional analyses adding psychotic symptoms (PANSS Total score) as a covariate.
Higher lifetime and current dose associated to left lateral ventricle increase (b = 0.33, P = 0.033; b = 0.307, P = 0.042, respectively) and right and left accumbens decrease (b = −0.405, P = 0.013, b = −0.404, P = 0.010; b = −0.302, P = 0.027, b = −0.282, P = 0.036, respectively) in schizophrenia but not in other psychoses. When PANSS was added to the model, the findings remained regarding right and left accumbens, but not regarding left lateral ventricle.
It seems that antipsychotic medication affects the brain in schizophrenia, but not in the heterogeneous group of other psychoses. In schizophrenia, brain changes associated to antipsychotic medication cannot be explained by illness duration or symptom severity.
Disclosure of interest
The authors have not supplied their declaration of competing interest.
Daily use of high-potency cannabis has been reported to carry a high risk for developing a psychotic disorder. However, the evidence is mixed on whether any pattern of cannabis use is associated with a particular symptomatology in first-episode psychosis (FEP) patients.
We analysed data from 901 FEP patients and 1235 controls recruited across six countries, as part of the European Network of National Schizophrenia Networks Studying Gene-Environment Interactions (EU-GEI) study. We used item response modelling to estimate two bifactor models, which included general and specific dimensions of psychotic symptoms in patients and psychotic experiences in controls. The associations between these dimensions and cannabis use were evaluated using linear mixed-effects models analyses.
In patients, there was a linear relationship between the positive symptom dimension and the extent of lifetime exposure to cannabis, with daily users of high-potency cannabis having the highest score (B = 0.35; 95% CI 0.14–0.56). Moreover, negative symptoms were more common among patients who never used cannabis compared with those with any pattern of use (B = −0.22; 95% CI −0.37 to −0.07). In controls, psychotic experiences were associated with current use of cannabis but not with the extent of lifetime use. Neither patients nor controls presented differences in depressive dimension related to cannabis use.
Our findings provide the first large-scale evidence that FEP patients with a history of daily use of high-potency cannabis present with more positive and less negative symptoms, compared with those who never used cannabis or used low-potency types.
The Square Kilometre Array (SKA) is a planned large radio interferometer designed to operate over a wide range of frequencies, and with an order of magnitude greater sensitivity and survey speed than any current radio telescope. The SKA will address many important topics in astronomy, ranging from planet formation to distant galaxies. However, in this work, we consider the perspective of the SKA as a facility for studying physics. We review four areas in which the SKA is expected to make major contributions to our understanding of fundamental physics: cosmic dawn and reionisation; gravity and gravitational radiation; cosmology and dark energy; and dark matter and astroparticle physics. These discussions demonstrate that the SKA will be a spectacular physics machine, which will provide many new breakthroughs and novel insights on matter, energy, and spacetime.