Combined social cognitive and neurocognitive rehabilitation strategies in schizophrenia: neuropsychological and psychopathological influences on Theory of Mind improvement.

BACKGROUND: Neurocognitive and social cognitive impairments represent important treatment targets in schizophrenia, as they are significant predictors of functional outcome. Different rehabilitative interventions have recently been developed, addressing both cognitive and psychosocial domains. Although promising, results are still heterogeneous and predictors of treatment outcome are not yet identified. In this study we evaluated the efficacy of two newly developed social cognitive interventions, respectively based on the use of videotaped material and comic strips, combined with domain-specific Cognitive Remediation Therapy (CRT). We also analysed possible predictors of training outcome, including basal neurocognitive performance, the degree of cognitive improvement after CRT and psychopathological variables. METHOD: Seventy-five patients with schizophrenia treated with CRT, were randomly assigned to: social cognitive training (SCT) group, Theory of Mind Intervention (ToMI) group, and active control group (ACG). RESULTS: ANOVAs showed that SCT and ToMI groups improved significantly in ToM measures, whereas the ACG did not. We reported no influences of neuropsychological measures and improvement after CRT on changes in ToM. Both paranoid and non-paranoid subjects improved significantly after ToMI and SCT, without differences between groups, despite the better performance in basal ToM found among paranoid patients. In the ACG only non-paranoid patients showed an improvement in non-verbal ToM. CONCLUSION: Results showed that both ToMI and SCT are effective in improving ToM in schizophrenia with no influence of neuropsychological domains. Our data also suggest that paranoid symptoms may discriminate between different types of ToM difficulties in schizophrenia.

Adverse childhood experiences influence white matter microstructure in patients with bipolar disorder.

BACKGROUND: Bipolar disorder (BD) is associated with adverse childhood experiences (ACE), which worsen the lifetime course of illness, and with signs of widespread disruption of white matter (WM) integrity in adult life. ACE are associated with changes in WM microstructure in healthy humans. METHOD: We tested the effects of ACE on diffusion-tensor imaging (DTI) measures of WM integrity in 80 in-patients affected by a major depressive episode in the course of BD. We used whole-brain tract-based spatial statistics in the WM skeleton with threshold-free cluster enhancement of DTI measures of WM microstructure: axial, radial and mean diffusivity, and fractional anisotropy. RESULTS: ACE hastened the onset of illness. We observed an inverse correlation between the severity of ACE and DTI measures of axial diffusivity in several WM fibre tracts contributing to the functional integrity of the brain and including the corona radiata, thalamic radiations, corpus callosum, cingulum bundle, superior longitudinal fasciculus, inferior fronto-occipital fasciculus and uncinate fasciculus. CONCLUSIONS: Axial diffusivity reflects the integrity of axons and myelin sheaths, and correlates with functional connectivity and with higher-order abilities such as reasoning and experience of emotions. In patients with BD axial diffusivity is increased by lithium treatment. ACE might contribute to BD pathophysiology by hampering structural connectivity in critical cortico-limbic networks.

Emotional reactivity in chronic schizophrenia: structural and functional brain correlates and the influence of adverse childhood experiences.

BACKGROUND: Despite behavioural signs of flattened affect, patients affected by schizophrenia show enhanced sensitivity to negative stimuli. The current literature concerning neural circuitry for emotions supports dysregulations of cortico-limbic networks, but gives contrasting results. Adverse childhood experiences (ACEs) could persistently influence emotional regulation and neural correlates of response to emotional stimuli in healthy humans. This study evaluated the effect of ACEs and chronic undifferentiated schizophrenia on neural responses to emotional stimuli (negative facial expression). METHOD: Brain blood-oxygen-level-dependent functional magnetic resonance imaging neural responses to a face-matching paradigm, and regional grey matter (GM) volumes were studied at 3.0 T in the amygdala, hippocampus, anterior cingulated cortex (ACC) and prefrontal cortex (PFC). The severity of ACEs was assessed. Participants included 20 consecutively admitted in-patients affected by chronic undifferentiated schizophrenia, and 20 unrelated healthy volunteers from the general population. RESULTS: Patients reported higher ACEs than controls. Worse ACEs proportionally led to decreasing responses in the amygdala and hippocampus, and to increasing responses in the PFC and ACC in all participants. Patients showed higher activations in the amygdala and hippocampus, and lower activations in the PFC and ACC. Higher ACEs were associated with higher GM volumes in the PFC and ACC, and schizophrenia was associated with GM reduction in all studied regions. CONCLUSIONS: Structural and functional brain correlates of emotional reactivity are influenced by both current chronic undifferentiated schizophrenia and the severity of past ACEs.

A symptom-specific analysis of the effect of high-frequency left or low-frequency right transcranial magnetic stimulation over the dorsolateral prefrontal cortex in major depression.

BACKGROUND: We have investigated the efficacy of high-frequency left (HFL) versus low-frequency right (LFR) repetitive transcranial magnetic stimulation (rTMS) in depression, focusing on specific symptoms as possible predictors of outcome for these two different types of stimulation. METHOD: Seventy-four outpatients with a major depressive episode treated with an adequate antidepressant dosage for at least 4 weeks were included in our study and randomly assigned to two different groups: HFL or LFR rTMS. The Hamilton Rating Scale for Depression (HAM-D) items were pooled into 6 factors to evaluate specific symptoms as possible predictors of response. RESULTS: Twenty-one out of 32 patients (65.6%) and 24 out of 42 patients (57.1%) were responders in the HFL and LFR groups, respectively. No significant difference in response rate was observed. Considering the whole sample, we found an inverse correlation between activity and HAM-D score reduction and a significant positive relation between somatic anxiety and outcome. An inverse correlation between psychic anxiety and HAM-D score reduction emerged considering the HFL group. In the LFR group, there was a significant negative relationship between baseline activity and the outcome. CONCLUSION: These findings support the hypothesis that LFR rTMS could be as effective as HFL rTMS and more suitable for patients with a higher anxiety degree, particularly in bipolar patients.

Computer-aided neurocognitive remediation in schizophrenia: durability of rehabilitation outcomes in a follow-up study.

Cognitive deficits in patients with schizophrenia constitute a limiting factor to the chances of rehabilitation of daily living abilities, like personal and relational autonomy and working ability. Cognitive Remediation Therapy (CRT) is a rehabilitative technique that aims at the recovery of single cognitive functions through the execution of massive exercises of impaired cognitive domains. This study aims to establish if the results achieved through an intensive deficit-specific neurocognitive treatment of three months duration, were maintained over time. The sample consists in 100 patients diagnosed with schizophrenia according to the criteria of DSM IV. Patients were assessed on cognitive and daily functioning at baseline, after 3 months of either CRT or placebo training added to their standard rehabilitation treatment, at 6 month and 12-month follow-up. Results showed significant changes that were maintained at follow-up for executive function, attention and psychomotor coordination. Moreover the significant improvement in daily functioning was maintained at 6 and 12-month follow-up. In conclusion improvements in cognitive functions and daily functioning achieved through the association of CRT and standard rehabilitation treatment persist over time after the conclusion of the training period.

Changes in medial prefrontal cortex neural responses parallel successful antidepressant combination of venlafaxine and light therapy.

Few pilot prospective studies performed BOLD fMRI before and after treatment in order to define the neural correlates of antidepressant response. To determine how antidepressant treatment influences the pattern of neural response to a task targeting the depressive biases in information processing (moral valence decision), eight depressed inpatients were treated with combined venlafaxine and light therapy for four weeks. Brain BOLD functional magnetic resonance imaging on a 3.0 Tesla scanner was performed before and after treatment. Treatment and moral value of the stimuli showed the most significant interaction in right medial frontal gyrus (BA 10), where also clinical status was found to be inversely correlated with response to negative stimuli after treatment. A significant interaction of treatment and valence of the stimuli was also detected in other areas that have been widely associated with the depressive illness.

Response to SSRIs and role of the hormonal therapy in post-menopausal depression.

The aim of this study is to prospectively evaluate the antidepressant response to SSRIs in depressed post-menopausal women with or without hormonal therapy (HT), and to analyze the possible influence of basal serum levels of gonadotropins and sexual hormones on the antidepressant response. 170 post-menopausal women with a depressive episode (DSM-IV criteria)--47 on HT and 123 not on HT--started the treatment with an SSRI. Depressive symptoms were assessed at baseline and 7 weeks thereafter by raters blind to treatment regimen. Response rates were 63.2% in the group without HT and 83.7% in the HT group (p=0.013). An inverse correlation emerged between the basal levels of LH and the improvement in HRSD scores (p=0.001) in the group without HT. In conclusion, HT appeared to improve the antidepressant response to SSRIs. Furthermore, in post-menopausal women, LH basal levels may be taken into account as possible predictor of response.

Abnormal brain oscillations persist after recovery from bipolar depression.

When directly perturbed in healthy subjects, premotor cortical areas generate electrical oscillations in the beta range (20-40Hz). In schizophrenia, major depressive disorder and bipolar disorder (BD), these oscillations are markedly reduced, in terms of amplitude and frequency. However, it still remains unclear whether these abnormalities can be modulated over time, or if they can be still observed after treatment. Here, we employed transcranial magnetic stimulation (TMS) combined with EEG to assess the frontal oscillatory activity in eighteen BD patients before/after antidepressant treatments (sleep deprivation and light therapy), relative to nine healthy controls. In order to detect dominant frequencies, event related spectral perturbations (ERSP) were computed for each TMS/EEG session in all participants, using wavelet decomposition. The natural frequency at which the cortical circuit oscillates was calculated as the frequency value with the largest power across 300ms post-stimulus time interval. Severity of depression markedly decreased after treatment with 12 patients achieving response and nine patients achieving remission. TMS/EEG resulted in a significant activation of the beta/gamma band response (21-50Hz) in healthy controls. In patients, the main frequencies of premotor EEG responses to TMS did not significantly change before/after treatment and were always significantly lower than those of controls (11-27Hz) and comparable in patients achieving remission and in those not responding to treatment. These results suggest that the reduction of natural frequencies is a trait marker of BD, independent from the clinical status of the patients. The present findings shed light on the neurobiological underpinning of severe psychiatric disorders and demonstrate that TMS/EEG represents a unique tool to develop biomarkers in psychiatry.

Cognitive remediation and functional improvement in schizophrenia: Is it a matter of size?

BACKGROUND: Cognitive Remediation represents the best available tool to treat cognitive deficits in schizophrenia and evidence suggests an effect also on global functioning. However, the relationship between cognitive and functional improvement is not yet fully elucidated: do cognitive changes need to be of a definite size and/or encompass a certain number of domains in order to impact on daily functioning? This study aims to explore the role of cognitive improvement, evaluated both quantitatively and qualitatively through the use of Italian equivalent scores, on the daily functioning of patients. As secondary goal, the influence of demographic, clinical and neuropsychological variables on functional outcome was also systematically investigated. METHODS: One hundred subjects with a diagnosis of schizophrenia underwent 36 sessions of Cognitive Remediation and were evaluated at baseline and after the training with the Brief Assessment of Cognition in Schizophrenia and the Quality of Life Scale. RESULTS: A total of 70% of patients improved in at least one cognitive domain and over 50% obtained a normalized score. Among the clinical and neurocognitive factors examined, the only significant predictor of quality of life's improvement was the proportion of cognitive functions that reached an equivalent score of "normal". CONCLUSIONS: This study suggests that improvements in daily functioning depend on the achievement of a cognitive profile as much as possible "normal", harmonious and balanced, supporting the idea that a qualitative leap in cognition is needed in order to gain an advantage in real life activities.

A double-blind, randomised, controlled clinical trial of acetyl-L-carnitine vs. amisulpride in the treatment of dysthymia.

AIM: Evaluation of the effect of acetyl-L-carnitine (ALCAR) vs. amisulpride measured by total Hamilton Depression Rating Scale score (HAM-D(21)) in patients with pure dysthymia (DSM IV). Two hundred and four patients were randomised and treated with ALCAR 500 mg b.i.d. or amisulpride 50 mg u.i.d. in a double-blind study, for 12 weeks. RESULTS: A solid improvement of HAM-D(21) was observed in both treatment groups throughout the study. The results did not disclose statistically significant differences between treatments, although the confidence interval for the non-inferiority of the primary end-point exceeded the pre-established limit of 2 by 0.46 points. According to a non-inferiority margin of 3 (considered acceptable by recent published data) the primary end-point could have been fully satisfied. CDRS, MADRS and CGI, employed to further measure the clinical outcome, reported similar results in both treatment groups. The greater tolerability of ALCAR is of clinical relevance considering the chronicity of dysthymia, which often requires prolonged treatment.

Modulation by muscarinic antagonists of the response to carbon dioxide challenge in panic disorder.

BACKGROUND: Panic attacks can be induced in persons with panic disorder by inhalation of carbon dioxide. Hypercapnia also elicits a reflex hyperventilation, which is controlled in part by cholinergic mechanisms. This study investigated whether the exaggerated response to carbon dioxide in panic disorder (PD) can be modulated by antagonists of muscarinic cholinergic receptors. METHODS: Twelve patients with PD received biperiden hydrochloride (a muscarinic antagonist that crosses the blood-brain barrier), pirenzepine hydrochloride (a muscarinic antagonist that does not cross the blood-brain barrier), or placebo 2 hours before a 35% carbon dioxide-65% oxygen respiratory challenge (vs air as a placebo) on 3 separate days, in a double-blind, random crossover design. RESULTS: According to patients' self-ratings of subjective anxiety, inhalation of the carbon dioxide/oxygen mixture provoked a significant and intense response after treatment with pirenzepine and placebo. After biperiden treatment, however, hypercapnia elicited a response profile similar to that elicited by air, whereby subjective anxiety remained similar to preinhalation levels. CONCLUSIONS: Consistent with the hypothesis of the study, a centrally active muscarinic antagonist can block the response to carbon dioxide commonly observed in subjects with PD.

Abnormalities of cyclic adenosine monophosphate signaling in platelets from untreated patients with bipolar disorder.

BACKGROUND: Abnormalities in the cyclic adenosine monophosphate (cAMP)-dependent phosphorylation system have been recently reported in patients with bipolar disorder. We evaluated the immunoreactivity of the regulatory and catalytic subunits of cAMP-dependent protein kinase (protein kinase A) and 1 of its substrates, Rap1, in platelets from untreated euthymic, manic, and depressed patients with bipolar disorder and healthy subjects. METHODS: Platelets were collected from 112 drug-free patients with bipolar disorder (52 euthymic, 29 depressed, and 31 manic) and 62 healthy subjects. The levels of cAMP-dependent protein kinase and Rap1 were assessed by Western blot analysis, immunostaining, and computer-assisted imaging. RESULTS: The immunolabeling of the catalytic subunit of cAMP-dependent protein kinase was significantly different among groups (P<.001), with higher values in untreated depressed and manic patients with bipolar disorder compared with untreated euthymic patients with bipolar disorder and healthy subjects. No significant differences were found in the immunolabeling of the regulatory subunits (type I and type II) of cAMP-dependent protein kinase. The immunolabeling of Rap1 was significantly higher (P<.001) in untreated euthymic, depressed, and manic patients than in healthy persons. CONCLUSIONS: Levels of Rap1 and the catalytic subunit of cAMP-dependent protein kinase are altered in the platelets of bipolar patients. These findings may provide clues toward understanding the involvement of cAMP signaling in the pathogenesis of bipolar disorder.

Deranged anterior pituitary responsiveness to hypothalamic hormones in depressed patients.

Abnormal anterior pituitary (AP) responsiveness to acute administration of thyrotropin-releasing hormone (TRH) and luteinizing hormone-follicle stimulating hormone-releasing hormone (LH-RH) was investigated in 14 patients (two men and 12 women) suffering from primary affective disorders. In ten, TRH, 500 microgram given intravenously, induced a rise in plasma growth hormone (GH) level, while in eight patients it induced a rise in plasma levels of FSH or LH or both. When LH-RH, 150 microgram was administered intravenously to ten patients, it induced a rise in plasma GH level in one patient and increased plasma prolactin level in three patients. Collectively, in only three of 14 patients was conventional AP responsiveness to hypothalamic neurohormones present. These findings demonstrate the existence of a profound derangement of AP responsiveness to hypothalamic neurohormones in depressed patients and suggest that a primary alteration in the physiologic links between the central nervous system and the AP may be at the origin of the neuroendocrine disturbance.

Analysis of the D4 dopamine receptor gene variant in an Italian schizophrenia kindred.

BACKGROUND: Among the different dopamine receptors, the D4 dopamine receptor is of particular interest in schizophrenia because of its high affinity for the atypical neuroleptic clozapine. Recently, the gene for the D4 dopamine receptor has been cloned and a new and intriguing polymorphism has been described. Different versions of the receptor have varying affinity for clozapine, and thus variant froms of D4 with differing pharmacologic activity exist in the human population. Our hypothesis was that these variants play a role in susceptibility to psychotic illness. Thus, our objective was to test the D4 dopamine receptor genes for linkage to schizophrenia. METHODS: Our genetic linkage study was carried out in a large Italian kindred segregating schizophrenia. Diagnoses were made by using a structured clinical interview and a consensus diagnosis was established. For the computer analysis, 80 members of the family were constructed into a linked set of relatives with 15 of these individuals affected by schizophrenia. The functional variants of the D4 dopamine receptor gene were identified by a combination of Southern blot techniques and the polymerase chain reaction. The gene for tyrosine hydroxylase (TH) was also tested for linkage to schizophrenia in this family. Linkage analyses were done with both a single-locus and a two-locus model. RESULTS: Our results revealed significantly negative lod scores in the region of the D4 dopamine receptor gene and the TH gene. The application of different models of transmission for schizophrenia had an effect on the magnitude of the lod scores, but did not modify the direction of the results. CONCLUSIONS: Our results provide significant evidence for exclusion for linkage between schizophrenia and the dopamine D4 receptor gene and the TH gene under the models specified. Furthermore, we tabulated the distribution of D4 dopamine gene variants in the diseased vs healthy individuals in the family and the results showed that no specific form of the receptor gene is significantly associated with the presence of schizophrenia in the family. Our study does not exclude the possibility that regulatory elements of the D4 dopamine gene located elsewhere in the genome may be involved in the etiology of schizophrenia.

White matter microstructure in bipolar disorder is influenced by the serotonin transporter gene polymorphism 5-HTTLPR.

Bipolar disorder (BD) is associated with signs of widespread disruption of white matter (WM) integrity. A polymorphism in the promoter of the serotonin transporter (5-HTTLPR) influenced functional cortico-limbic connectivity in healthy subjects and course of illness in BD, with the short (s) allele being associated with lower functional connectivity, and with earlier onset of illness and poor response to treatment. We tested the effects of 5-HTTLPR on diffusion tensor imaging (DTI) measures of WM microstructure in 140 inpatients, affected by a major depressive episode in course of BD, of Italian descent. We used whole brain tract-based spatial statistics in the WM skeleton with threshold-free cluster enhancement of DTI measures of WM microstructure: axial, radial and mean diffusivity and fractional anisotropy. Compared with l/l homozygotes, 5-HTTLPR*s carriers showed significantly increased radial and mean diffusivity in several brain WM tracts, including corpus callosum, cingulum bundle, uncinate fasciculus, corona radiata, thalamic radiation, inferior and superior longitudinal fasciculus and inferior fronto-occipital fasciculus. An increase of mean and radial diffusivity, perpendicular to the main axis of the WM tract, is thought to signify increased space between fibers, thus suggesting demyelination or dysmyelination, or loss of bundle coherence. The effects of 5-HTTLPR on the anomalous emotional processing in BD might be mediated by changes of WM microstructure in key WM tracts contributing to the functional integrity of the brain.

Fronto-limbic disconnection in bipolar disorder.

BACKGROUND: Bipolar disorder (BD) is a severe, disabling and life-threatening illness. Disturbances in emotion and affective processing are core features of the disorder with affective instability being paralleled by mood-congruent biases in information processing that influence evaluative processes and social judgment. Several lines of evidence, coming from neuropsychological and imaging studies, suggest that disrupted neural connectivity could play a role in the mechanistic explanation of these cognitive and emotional symptoms. The aim of the present study is to investigate the effective connectivity in a sample of bipolar patients. METHODS: Dynamic causal modeling (DCM) technique was used to study 52 inpatients affected by bipolar disorders consecutively admitted to San Raffaele hospital in Milano and forty healthy subjects. A face-matching task was used as activation paradigm. RESULTS: Patients with BD showed a significantly reduced endogenous connectivity in the DLPFC to Amy connection. There was no significant group effect upon the endogenous connection from Amy to ACC, from ACC to Amy and from DLPFC to ACC. CONCLUSIONS: Both DLPFC and ACC are part of a network implicated in emotion regulation and share strong reciprocal connections with the amygdale. The pattern of abnormal or reduced connectivity between DLPFC and amygdala may reflect abnormal modulation of mood and emotion typical of bipolar patients.

Abnormal cortico-limbic connectivity during emotional processing correlates with symptom severity in schizophrenia.

BACKGROUND: Impaired emotional processing is a core feature of schizophrenia (SZ). Consistent findings suggested that abnormal emotional processing in SZ could be paralleled by a disrupted functional and structural integrity within the fronto-limbic circuitry. The effective connectivity of emotional circuitry in SZ has never been explored in terms of causal relationship between brain regions. We used functional magnetic resonance imaging and Dynamic Causal Modeling (DCM) to characterize effective connectivity during implicit processing of affective stimuli in SZ. METHODS: We performed DCM to model connectivity between amygdala (Amy), dorsolateral prefrontal cortex (DLPFC), ventral prefrontal cortex (VPFC), fusiform gyrus (FG) and visual cortex (VC) in 25 patients with SZ and 29 HC. Bayesian Model Selection and average were performed to determine the optimal structural model and its parameters. RESULTS: Analyses revealed that patients with SZ are characterized by a significant reduced top-down endogenous connectivity from DLPFC to Amy, an increased connectivity from Amy to VPFC and a decreased driving input to Amy of affective stimuli compared to HC. Furthermore, DLPFC to Amy connection in patients significantly influenced the severity of psychopathology as rated on Positive and Negative Syndrome Scale. CONCLUSIONS: Results suggest a functional disconnection in brain network that contributes to the symptomatic outcome of the disorder. Our findings support the study of effective connectivity within cortico-limbic structures as a marker of severity and treatment efficacy in SZ.

Combined neurocognitive and metacognitive rehabilitation in schizophrenia: Effects on bias against disconfirmatory evidence.

BACKGROUND: A Metacognitive Training for Schizophrenia patients (MCT) was developed to target the cognitive biases that characterize the illness. Results suggest positive MCT effects encompassing several aspects of psychopathology and subjective well-being. There are still open questions concerning the effect on different cognitive biases and the interplay between them and both psychopathology and neurocognition. Specifically, the bias against disconfirmatory evidence (BADE) has never been tested in previous trials on MCT. In this study we evaluated the feasibility of MCT combined with a cognitive remediation therapy (CACR) in schizophrenia and its effect on BADE. Moreover, we investigated the relationships between BADE and both neuropsychology and psychopathology, taking into account mutual influences on the degree of improvement. METHODS: Fifty-seven schizophrenia outpatients were randomly assigned to CACR + control group or MCT+CACR and assessed at baseline and after treatment for psychopathology, neurocognition and BADE. RESULTS: After MCT+CACR patients showed significantly greater improvements on BADE. Although BADE baseline performances correlated with several cognitive domains, no association was found between BADE improvement and neurocognitive nor psychopathological measures. CONCLUSIONS: This study enlightened for the first time the efficacy of MCT+CACR on BADE in schizophrenia, suggesting the importance to develop a more specific intervention tailored on individual needs of patients.

Effects of acute intravenous clomipramine on obsessive-compulsive symptoms and response to chronic treatment.

The aim of this study was to test the hypothesis that obsessive-compulsive symptoms are temporarily worsened by acute intravenous clomipramine, suggesting that there is a basal hypersensitivity of serotonin (5-HT) receptors in obsessive-compulsive (OC) patients. We also investigated the relationship of the effects of acute (intravenous) and chronic (oral) administration of clomipramine. Twenty-eight OC patients were recruited. The first part of the study included placebo and clomipramine infusions and monitoring of OC symptoms by 100 mm Visual Analogue self-rated scales (VAS). There was significant worsening of obsessions in the whole sample during clomipramine infusion. The second part included standardized 10-week oral treatments with clomipramine and evaluation of clinical efficacy. Among the 18 patients who completed the second part of the study, oral clomipramine significantly reduced OC symptoms, but OC patients who had become worse after clomipramine infusion showed higher Y-BOCS scores.

Further studies on the major histocompatibility complex as a genetic marker for schizophrenia.

Our results seem to indicate the existence of a locus in the major histocompatibity complex (MHC) region, correlated to schizophrenic illness and strictly linked to the loci HL-A and MLR. The associations found between these last loci and the disease can probably be explained by a linkage disequilibrium or a selective pressure between the allelles of the three loci. Our results also indicate that the genetic systems investigated may be useful diagnostically as a genetic marker for schizophrenia. But the real meaning of their relationships to the illness has to be further investigated.