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ABSTRACT: INTRODUCTION: Verbal auditory hallucinations (VAHs) are experienced as spoken voices which seem to originate in the extracorporeal environment or inside the head. Animal and human research has identified a 'where' pathway for sound processing comprising the planum temporale, the middle frontal gyrus and the inferior parietal lobule. We hypothesize that increased activity of that 'where' pathway mediates the exteriorization of VAHs. METHODS: The fMRI scans of 52 right-handed psychotic patients experiencing frequent VAHs were compared with the reported location of hallucinations, as rated with the aid of the PSYRATS-AHRS. For each subject, a unique VAH activation model was created based on the VAH timings, and subsequently convolved with a gamma function to model the hemodynamic response. In order to examine the neurofunctional equivalents of perceived VAH location, second-level group effects of subjects experiencing either internal (n=24) or external (n=28) VAHs were contrasted within planum temporale, middle frontal gyrus, and inferior parietal lobule regions of interest (ROIs). RESULTS: Three ROIs were tested for increased activity in relation with the exteriorization of VAHs. The analysis revealed a left-sided medial planum temporale and a right-sided middle frontal gyrus cluster of increased activity. No significant activity was found in the inferior parietal lobule. CONCLUSIONS: Our study indicates that internal and external VAHs are mediated by a fronto-temporal pattern of neuronal activity while the exteriorization of VAHs stems from additional brain activity in the auditory 'where' pathway, comprising the planum temporale and prefrontal regions.
Biological Psychiatry 03/2013; · 8.28 Impact Factor
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ABSTRACT: This article reviews the treatment of hallucinations in schizophrenia. The first treatment option for hallucinations in schizophrenia is antipsychotic medication, which can induce a rapid decrease in severity. Only 8% of first-episode patients still experience mild to moderate hallucinations after continuing medication for 1 year. Olanzapine, amisulpride, ziprasidone, and quetiapine are equally effective against hallucinations, but haloperidol may be slightly inferior. If the drug of first choice provides inadequate improvement, it is probably best to switch medication after 2-4 weeks of treatment. Clozapine is the drug of choice for patients who are resistant to 2 antipsychotic agents. Blood levels should be above 350-450 μg/ml for maximal effect. For relapse prevention, medication should be continued in the same dose. Depot medication should be considered for all patients because nonadherence is high. Cognitive-behavioral therapy (CBT) can be applied as an augmentation to antipsychotic medication. The success of CBT depends on the reduction of catastrophic appraisals, thereby reducing the concurrent anxiety and distress. CBT aims at reducing the emotional distress associated with auditory hallucinations and develops new coping strategies. Transcranial magnetic stimulation (TMS) is capable of reducing the frequency and severity of auditory hallucinations. Several meta-analyses found significantly better symptom reduction for low-frequency repetitive TMS as compared with placebo. Consequently, TMS currently has the status of a potentially useful treatment method for auditory hallucinations, but only in combination with state of the art antipsychotic treatment. Electroconvulsive therapy (ECT) is considered a last resort for treatment-resistant psychosis. Although several studies showed clinical improvement, a specific reduction in hallucination severity has never been demonstrated.
Schizophrenia Bulletin 02/2012; 38(4):704-14. · 8.80 Impact Factor
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Simone de Jong,
Marco P M Boks,
Tova F Fuller,
Eric Strengman,
Esther Janson,
Carolien G F de Kovel,
Anil P S Ori,
Nancy Vi,
Flip Mulder, Jan Dirk Blom,
Birte Glenthøj,
Chris D Schubart,
Wiepke Cahn,
René S Kahn,
Steve Horvath,
Roel A Ophoff
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ABSTRACT: Despite large-scale genome-wide association studies (GWAS), the underlying genes for schizophrenia are largely unknown. Additional approaches are therefore required to identify the genetic background of this disorder. Here we report findings from a large gene expression study in peripheral blood of schizophrenia patients and controls. We applied a systems biology approach to genome-wide expression data from whole blood of 92 medicated and 29 antipsychotic-free schizophrenia patients and 118 healthy controls. We show that gene expression profiling in whole blood can identify twelve large gene co-expression modules associated with schizophrenia. Several of these disease related modules are likely to reflect expression changes due to antipsychotic medication. However, two of the disease modules could be replicated in an independent second data set involving antipsychotic-free patients and controls. One of these robustly defined disease modules is significantly enriched with brain-expressed genes and with genetic variants that were implicated in a GWAS study, which could imply a causal role in schizophrenia etiology. The most highly connected intramodular hub gene in this module (ABCF1), is located in, and regulated by the major histocompatibility (MHC) complex, which is intriguing in light of the fact that common allelic variants from the MHC region have been implicated in schizophrenia. This suggests that the MHC increases schizophrenia susceptibility via altered gene expression of regulatory genes in this network.
PLoS ONE 01/2012; 7(6):e39498. · 4.09 Impact Factor
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ABSTRACT: Low-frequency repetitive transcranial magnetic stimulation (rTMS) applied to the left temporoparietal area (TP) has been investigated as a treatment method for auditory verbal hallucinations (AVH) yielding inconsistent results. In vitro studies have indicated that the effects of low-frequency rTMS can be enhanced by a brief pretreatment phase consisting of high-frequency rTMS (i.e., priming rTMS).
The aim of this single-blind, randomized controlled study was to investigate whether the effects of rTMS on AVH can be enhanced with priming rTMS.
Twenty-three patients with medication-resistant AVH were randomized over two groups: one receiving low-frequency rTMS preceded by 5 minutes of 6 Hertz rTMS; and another receiving low-frequency rTMS without priming. Both treatments were directed at the left TP. The total duration of stimulation was equal in the two groups, namely, 15 sessions of 20 minutes each. The severity of AVH and other psychotic features were measured with the aid of the Auditory Hallucination Rating Scale (AHRS), the Positive and Negative Syndrome Scale (PANSS) and the Psychotic Symptom Rating Scales (PSYRATS).
The severity of AVH and other psychotic symptoms in the group with priming was not significantly lower after 3 weeks of treatment in comparison to baseline. The group treated with standard rTMS showed a trend toward improvement after 3 weeks of treatment. No significant differences were observed on any of the rating scales between the group with and without priming.
This study does not provide evidence that priming rTMS is an effective treatment for AVH.
Brain Stimulation 10/2011; 5(4):554-9. · 3.76 Impact Factor
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ABSTRACT: While auditory verbal hallucinations (AVH) are most characteristic for schizophrenia, they also occur in nonpsychotic individuals in the absence of a psychiatric or neurological disorder and in the absence of substance abuse. At present, it is unclear if AVH in these nonpsychotic individuals constitute the same phenomenon as AVH in psychotic patients. Comparing brain activation during AVH between nonpsychotic and psychotic individuals could provide important clues regarding this question. 21 nonpsychotic subjects with AVH and 21 matched psychotic patients indicated the presence of AVH during 3T functional magnetic resonance imaging (fMRI) scanning. To identify common areas of activation during the experience of AVH in both groups, a conjunction analysis was performed. In addition, a 2-sample t-test was employed to discover possible differences in AVH-related activation between the groups. Several common areas of activation were observed for the psychotic and nonpsychotic subjects during the experience of AVH, consisting of the bilateral inferior frontal gyri, insula, superior temporal gyri, supramarginal gyri and postcentral gyri, left precentral gyrus, inferior parietal lobule, superior temporal pole, and right cerebellum. No significant differences in AVH-related brain activation were present between the groups. The presence of multiple common areas of AVH-related activation in psychotic and nonpsychotic individuals, in the absence of significant differences, implicates the involvement of the same cortical network in the experience of AVH in both groups.
Schizophrenia Bulletin 04/2011; 38(5):1074-82. · 8.80 Impact Factor
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Christina W Slotema, Jan Dirk Blom,
Antoin D de Weijer,
Kelly M Diederen,
Rutger Goekoop,
Jasper Looijestijn,
Kirstin Daalman,
Anne-Marije Rijkaart,
René S Kahn,
Hans W Hoek,
Iris E C Sommer
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ABSTRACT: Several studies have applied low-frequency repetitive transcranial magnetic stimulation (rTMS) directed at the left temporoparietal area (TP) for the treatment of auditory verbal hallucinations (AVH), but findings on efficacy are inconsistent. Furthermore, recent functional magnetic resonance imaging (fMRI) studies indicate that the left TP is not a general focus of activation during the experience of AVH. The aims of this study are twofold: to investigate the effects of rTMS on AVH in a double blind, randomized, sham-controlled study; and to investigate whether the efficacy can be improved when rTMS is guided by individual fMRI scans of hallucinatory activation.
Sixty-two patients with medication-resistant AVH were randomized over three conditions: rTMS targeted at the area of maximal hallucinatory activation calculated from individual fMRI scans during AVH, rTMS directed at the left TP, and sham treatment. Repetitive TMS was applied during 15 sessions of 20 min each, at 1 Hz and 90% of the individual motor threshold. The severity of AVH and other psychotic symptoms were monitored during treatment and 3-month follow-up, with the Auditory Hallucination Rating Scale, the Positive and Negative Syndrome Scale, and the Psychotic Symptom Rating Scales.
The effects of fMRI-guided rTMS and left TP rTMS on the severity of AVH were comparable to those of sham treatment. No differences in severity of general psychotic symptoms were found among the three treatment conditions.
Low-frequency rTMS administered to the left TP or to the site of maximal hallucinatory activation is not more effective for medication-resistant AVH than sham treatment.
Biological psychiatry 03/2011; 69(5):450-6. · 8.93 Impact Factor
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ABSTRACT: Whereas auditory verbal hallucinations (AVHs) are most characteristic of schizophrenia, their presence has frequently been described in a continuum, ranging from severely psychotic patients to schizotypal personality disorder patients to otherwise healthy participants. It remains unclear whether AVHs at the outer borders of this spectrum are indeed the same phenomenon. Furthermore, specific characteristics of AVHs may be important indicators of a psychotic disorder.
To investigate differences and similarities in AVHs in psychotic and nonpsychotic individuals, the phenomenology of AVHs in 118 psychotic outpatients was compared to that in 111 otherwise healthy individuals, both experiencing AVHs at least once a month. The study was performed between September 2007 and March 2010 at the University Medical Center, Utrecht, the Netherlands. Characteristics of AVHs were quantified using the Psychotic Symptoms Rating Scales Auditory Hallucinations subscale.
The perceived location of voices (inside/outside the head), the number of voices, loudness, and personification did not differentiate between psychotic and healthy individuals. The most prominent differences between AVHs in healthy and psychotic individuals were the emotional valence of the content, the frequency of AVHs, and the control subjects had over their AVHs (all P values < .001). Age at onset of AVHs was at a significantly younger age in the healthy individuals (P < .001). In our sample, the negative emotional valence of the content of AVHs could accurately predict the presence of a psychotic disorder in 88% of the participants.
We cannot ascertain whether AVHs at the outer borders of the spectrum should be considered the same phenomenon, as there are both similarities and differences. The much younger age at onset of AVHs in the healthy subjects compared to that in psychotic patients may suggest a different pathophysiology. The high predictive value of the emotional content of voices implies that inquiring after the emotional content of AVHs may be a crucial step in the diagnosis of psychotic disorders in individuals hearing voices.
The Journal of Clinical Psychiatry 03/2011; 72(3):320-5. · 5.80 Impact Factor
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ABSTRACT: Alice in Wonderland syndrome (AIWS) is a rare cluster of CNS symptoms characterized by visual distortions (i.e. metamorphopsias), body image distortions, time distortions, and déjà experiences. Verbal auditory hallucinations (VAHs) are the most prevalent type of hallucination in adults with or without a history of psychiatric illness. Here, we report the case of a woman with AIWS, long-lasting VAHs, and various additional perceptual and mood symptoms.
Semi-structured interviews were used to assess symptoms, and functional MRI (fMRI) was employed to localize cerebral activity during self-reported VAHs. Treatment consisted of repetitive transcranial magnetic stimulation (rTMS) at a frequency of 1 Hz at T3P3, overlying Brodmann's area 40.
Activation during VAHs was observed bilaterally in the basal ganglia, the primary auditory cortex, the association auditory cortex, the temporal poles, and the anterior cingulated gyrus. The left and right inferior frontal gyri (Broca's area and its contralateral homologue) were involved, along with the dorsolateral prefrontal cortex. Interestingly, synchronized activation was observed in the primary visual cortex (areas V1 and V2), and the bilateral dorsal visual cortex. The higher visual association cortex also showed significant, but less prominent, activation. During the second week of rTMS treatment, not only the VAHs, but also the other sensory deceptions/distortions and mood symptoms showed complete remission. The patient remained free of any symptoms during a 4-month follow-up phase. After 8 months, when many of the original symptoms had returned, a second treatment phase with rTMS was again followed by complete remission.
This case indicates that VAHs and metamorphopsias in AIWS are associated with synchronized activation in both auditory and visual cortices. It also indicates that local rTMS treatment may have global therapeutic effects, suggesting an effect on multiple brain regions in a distributed network. Although a placebo effect cannot be ruled out, this case warrants further investigation of the effects of rTMS treatment in AIWS.
Psychopathology 01/2011; 44(5):337-44. · 1.82 Impact Factor
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ABSTRACT: Decreased language lateralization is a well-replicated finding in psychotic patients. It is currently unclear, however, whether this abnormality is related to a particular symptom of psychosis or to psychosis in general. It has been argued that decreased language lateralization may be related to auditory verbal hallucinations. To elucidate this, these hallucinations should be studied in isolation. Thirty-five patients with a psychotic disorder, 35 non-psychotic subjects with relatively isolated auditory verbal hallucinations and 35 healthy control subjects participated in this study. All subjects were scanned on a 3T magnetic resonance imaging scanner, while covertly performing a paced verbal fluency task. In order to measure performance on the task, one additional task block was presented during which subjects had to generate words overtly. In addition to calculating language lateralization indices, group-wise brain activation during verbal fluency was compared between the three groups. Task performance was nearly maximal for all groups and did not differ significantly between the groups. Compared with the healthy control subjects and non-psychotic subjects with auditory verbal hallucinations, language lateralization was significantly reduced for the patient group. In addition, the patients displayed significantly greater activity in the right precentral gyrus and left insula when compared with the healthy control subjects and the non-psychotic subjects with auditory verbal hallucinations. Furthermore, the patients showed greater activity in the right superior parietal lobule when compared with the healthy control subjects. Lateralization indices did not differ significantly between the non-psychotic subjects with auditory verbal hallucinations and the healthy control subjects. Moreover, there were no significant differences in brain activation during verbal fluency between the two non-psychotic groups. As language lateralization was not significantly reduced in the non-psychotic individuals with auditory verbal hallucinations, a direct relationship between auditory verbal hallucinations and decreased language lateralization can not be established at present.
Brain 12/2010; 133(Pt 12):3734-44. · 9.46 Impact Factor
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ABSTRACT: Activation in a network of language-related regions has been reported during auditory verbal hallucinations. It remains unclear, however, how this activation is triggered. Identifying brain regions that show significant signal changes preceding auditory hallucinations might reveal the origin of these hallucinations.
Twenty-four patients with a psychotic disorder indicated the presence of auditory verbal hallucinations during 3-Tesla functional magnetic resonance imaging by squeezing a handheld balloon. A one-sample t test was performed to reveal groupwise activation during hallucinations. To enable analysis of brain activation 6 to 0 seconds preceding hallucinations, a tailored 'selective averaging' method, without any a priori assumptions concerning the hemodynamic response profile, was performed. To control for motor-related activation, 15 healthy comparison subjects squeezed a balloon at matched time intervals.
Groupwise analysis during auditory verbal hallucinations revealed brain activation in bilateral (right more than left) language-related regions and bilateral motor regions. Prominent deactivation preceding these hallucinations was observed in the left parahippocampal gyrus. In addition, significant deactivation preceding hallucinations was found in the left superior temporal, right inferior frontal, and left middle frontal gyri as well as in the right insula and left cerebellum. No significant signal changes were revealed prior to the matched balloon squeezing among the comparison subjects.
Auditory verbal hallucinations in patients with a psychotic disorder are consistently preceded by deactivation of the parahippocampal gyrus. The parahippocampus has been hypothesized to play a central role in memory recollection, sending information from the hippocampus to the association areas. Dysfunction of this region could trigger inadequate activation of right language areas during auditory hallucinations.
American Journal of Psychiatry 04/2010; 167(4):427-35. · 12.54 Impact Factor
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ABSTRACT: Repetitive transcranial magnetic stimulation (rTMS) is a safe treatment method with few side effects. However, efficacy for various psychiatric disorders is currently not clear.
A literature search was performed from 1966 through October 2008 using PubMed, Ovid Medline, Embase Psychiatry, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, Database of Abstracts of Reviews of Effects, and PsycINFO. The following search terms were used: transcranial magnetic stimulation, TMS, repetitive TMS, psychiatry, mental disorder, psychiatric disorder, anxiety disorder, attention-deficit hyperactivity disorder, bipolar disorder, catatonia, mania, depression, obsessive-compulsive disorder, psychosis, posttraumatic stress disorder, schizophrenia, Tourette's syndrome, bulimia nervosa, and addiction.
Data were obtained from randomized, sham-controlled studies of rTMS treatment for depression (34 studies), auditory verbal hallucinations (AVH, 7 studies), negative symptoms in schizophrenia (7 studies), and obsessive-compulsive disorder (OCD, 3 studies). Studies of rTMS versus electroconvulsive treatment (ECT, 6 studies) for depression were meta-analyzed.
Standardized mean effect sizes of rTMS versus sham were computed based on pretreatment-posttreatment comparisons.
The mean weighted effect size of rTMS versus sham for depression was 0.55 (P < .001). Monotherapy with rTMS was more effective than rTMS as adjunctive to antidepressant medication. ECT was superior to rTMS in the treatment of depression (mean weighted effect size -0.47, P = .004). In the treatment of AVH, rTMS was superior to sham treatment, with a mean weighted effect size of 0.54 (P < .001). The mean weighted effect size for rTMS versus sham in the treatment of negative symptoms in schizophrenia was 0.39 (P = .11) and for OCD, 0.15 (P = .52). Side effects were mild, yet more prevalent with high-frequency rTMS at frontal locations.
It is time to provide rTMS as a clinical treatment method for depression, for auditory verbal hallucinations, and possibly for negative symptoms. We do not recommend rTMS for the treatment of OCD.
The Journal of Clinical Psychiatry 03/2010; 71(7):873-84. · 5.80 Impact Factor
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ABSTRACT: The literature on the possible neurobiologic correlates of auditory hallucinations is expanding rapidly. For an adequate understanding and linking of this emerging knowledge, a clear and uniform nomenclature is a prerequisite. The primary purpose of the present article is to provide an overview of the nomenclature and classification of auditory hallucinations.
Relevant data were obtained from books, PubMed, Embase, and the Cochrane Library.
The results are presented in the form of several classificatory arrangements of auditory hallucinations, governed by the principles of content, perceived source, perceived vivacity, relation to the sleep-wake cycle, and association with suspected neurobiologic correlates.
This overview underscores the necessity to reappraise the concepts of auditory hallucinations developed during the era of classic psychiatry, to incorporate them into our current nomenclature and classification of auditory hallucinations, and to test them empirically with the aid of the structural and functional imaging techniques currently available.
Cognitive and behavioral neurology: official journal of the Society for Behavioral and Cognitive Neurology 03/2010; 23(1):55-62. · 1.09 Impact Factor
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ABSTRACT: Individuals with an Islamic background who suffer from hallucinations often attribute these to djinns, invisible beings. The treatment of these hallucinations is complicated by the patients' reluctance to discuss them, and by their doubts concerning the usefulness of a biomedical treatment for a problem which they experience as metaphysical in nature. In this clinical lesson, we present case studies of three Moroccan patients who attributed their hallucinations to djinns. The first was a 30-year-old factory worker whose compulsive complaints had started when he saw a white figure in the basement who asked him 'What are you doing here?' The psychiatric diagnosis was obsessive-compulsive disorder. The patient was prescribed cognitive behavioural therapy, an SSRI and a consultation by the imam, but he refused. The second patient was a 25-year-old unemployed man, who had auditory hallucinations, delusions, behavioural problems, and alcohol and cannabis abuse. He heard voices which he attributed to maleficent djinns. He was diagnosed with schizophrenia, but his compliance with antipsychotics was insufficient. The imam who was consulted reassured him that his complaints were not caused by djinns. After prolonged treatment with clozapine and cutting down on cannabis use the patient recovered sufficiently to be discharged. The third patient was a 26-year-old unemployed woman who was hearing voices that her imam thought were caused by a djinn. She was examined because of serious self-mutilation and was diagnosed with a schizoaffective disorder. Treatment with an antipsychotic, lithium and valproic acid and a consultation by a second imam, who found no signs of evidence of djinns, was successful. We recommend to ask individuals with an Islamic background specifically whether djinns might be involved, especially in cases of mental problems and unexplained symptoms, and to seek the cooperation of a qualified imam or traditional healer for treatment purposes.
Nederlands tijdschrift voor geneeskunde 01/2010; 154:A973.
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ABSTRACT: This study proposes a theoretical framework which dissects auditory verbal hallucinations (AVH) into 2 essential components: audibility and alienation. Audibility, the perceptual aspect of AVH, may result from a disinhibition of the auditory cortex in response to self-generated speech. In isolation, this aspect leads to audible thoughts: Gedankenlautwerden. The second component is alienation, which is the failure to recognize the content of AVH as self-generated. This failure may be related to the fact that cerebral activity associated with AVH is predominantly present in the speech production area of the right hemisphere. Since normal inner speech is derived from the left speech area, an aberrant source may lead to confusion about the origin of the language fragments. When alienation is not accompanied by audibility, it will result in the experience of thought insertion. The 2 hypothesized components are illustrated using case vignettes.
Psychopathology 01/2010; 43(2):137-40. · 1.82 Impact Factor
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Iris E C Sommer,
Kelly M J Diederen, Jan-Dirk Blom,
Anne Willems,
Leila Kushan,
Karin Slotema,
Marco P M Boks,
Kirstin Daalman,
Hans W Hoek,
Sebastiaan F W Neggers,
René S Kahn
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ABSTRACT: The pathophysiology of auditory verbal hallucinations (AVH) is largely unknown. Several functional imaging studies have measured cerebral activation during these hallucinations, but sample sizes were relatively small (one to eight subjects) and findings inconsistent. In this study cerebral activation was measured using fMRI in 24 psychotic patients while they experienced AVH in the scanner and, in another session, while they silently generated words. All patients were right handed and diagnosed with schizophrenia, schizo-affective disorder or psychotic disorder not otherwise specified. Group analysis for AVH revealed activation in the right homologue of Broca's area, bilateral insula, bilateral supramarginal gyri and right superior temporal gyrus. Broca's area and left superior temporal gyrus were not activated. Group analysis for word generation in these patients yielded activation in Broca's and Wernicke's areas and to a lesser degree their right-sided homologues, bilateral insula and anterior cingulate gyri. Lateralization of activity during AVH was not correlated with language lateralization, but rather with the degree to which the content of the hallucinations had a negative emotional valence. The main difference between cerebral activity during AVH and activity during normal inner speech appears to be the lateralization. The predominant engagement of the right inferior frontal area during AVH may be related to the typical low semantic complexity and negative emotional content.
Brain 11/2008; 131(Pt 12):3169-77. · 9.46 Impact Factor
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ABSTRACT: Studies in the UK compared psychosis risks for first-degree relatives of White and African-Caribbean patients and found "normal" risks for the parents of Caribbean patients, but very high risks for siblings of second-generation Caribbean patients.
To compare the risk of non-affective psychotic disorder (NAPD) for the parents and siblings of Moroccan-Dutch patients to that for the parents and siblings of Dutch patients. The "Moroccan-Dutch" are Dutch residents of Moroccan origin (first or second generation).
Informants related to 29 Moroccan-Dutch and 63 Dutch patients were interviewed about the presence of psychiatric disorders in first-degree relatives (N=508), by means of the Family Interview for Genetic Studies.
The risks for NAPD in both parent groups were similar (age and sex-adjusted odds ratio 1.0; 95% CI: 0.3-3.8). However, among the siblings, the risk for NAPD was significantly higher for the Moroccan-Dutch than for the Dutch (sex-adjusted hazard ratio 4.5; 95% Confidence Interval: 1.5-14.0). This was due to a large number of cases among the brothers of the Moroccan-Dutch patients (N=14), not among their sisters (N=1). Owing to small numbers separate hazard ratios for the first and the second generation were not calculated.
These preliminary results suggest that environmental factors in the Netherlands have a great impact on the psychosis risk for male immigrants from Morocco.
Biological Psychiatry 07/2008; 104(1-3):274-8. · 8.28 Impact Factor
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ABSTRACT: There is only one previous report on the first-contact incidence of schizophrenia among immigrants in the Netherlands, which was based on a small number of cases, particularly for second generation immigrants. We conducted another two-year first-contact incidence study in the same geographical area, combined the data of both studies and compared risks over all four years. The incidence of schizophrenia was increased for all first generation non-Western immigrants. The risk was particularly high for second generation immigrants: the age- and gender-adjusted incidence rate ratio was 5.8 (95% CI, 2.9-11.4) for Moroccans, 2.9 (1.6-5.0) for Surinamese, 2.3 (1.0-5.4) for Turks, and 3.5 (1.8-6.8) for immigrants from other non-Western countries.
Schizophrenia Research 10/2006; 86(1-3):189-93. · 4.75 Impact Factor
