Relationship between cognition and age at onset of first-episode psychosis: comparative study between adolescents, young adults, and adults.

Psychotic disorders typically manifest from late adolescence to early adulthood, and an earlier onset might be associated with greater symptom severity and a worse long-term prognosis. This study aimed to compare the cognitive characteristics of patients with first-episode psychosis (FEP) by their age at onset. We included 298 patients diagnosed with FEP and classified them as having an early onset (EOS), youth onset (YOS), or adult onset (AOS) based on age limits of ≤ 18 years (N = 61), 19-24 years (N = 121), and ≥ 25 years (N = 116), respectively. Socio-demographic and clinical variables included age at baseline, gender, socio-economic status, antipsychotic medication, DSM-IV diagnoses assessed by clinical semi-structured interview, psychotic symptom severity, and age at onset. Neuropsychological assessment included six cognitive domains: premorbid intelligence, working memory, processing speed, verbal memory, sustained attention, and executive functioning. The EOS group had lower scores than the YOS or AOS groups in global cognition, executive functioning, and sustained attention. Although the scores in the YOS group were intermediate to those in the EOS and AOS groups for most cognitive factors, no statistically significant differences were detected between the YOS and AOS groups. Age at onset results in specific patterns of cognitive interference. Of note, impairment appears to be greater with EOS samples than with either YOS or AOS samples. A longitudinal study with a larger sample size is needed to confirm our findings.

A longitudinal study of gene expression in first-episode schizophrenia; exploring relapse mechanisms by co-expression analysis in peripheral blood.

Little is known about the pathophysiological mechanisms of relapse in first-episode schizophrenia, which limits the study of potential biomarkers. To explore relapse mechanisms and identify potential biomarkers for relapse prediction, we analyzed gene expression in peripheral blood in a cohort of first-episode schizophrenia patients with less than 5 years of evolution who had been evaluated over a 3-year follow-up period. A total of 91 participants of the 2EPs project formed the sample for baseline gene expression analysis. Of these, 67 provided biological samples at follow-up (36 after 3 years and 31 at relapse). Gene expression was assessed using the Clariom S Human Array. Weighted gene co-expression network analysis was applied to identify modules of co-expressed genes and to analyze their preservation after 3 years of follow-up or at relapse. Among the 25 modules identified, one module was semi-conserved at relapse (DarkTurquoise) and was enriched with risk genes for schizophrenia, showing a dysregulation of the TCF4 gene network in the module. Two modules were semi-conserved both at relapse and after 3 years of follow-up (DarkRed and DarkGrey) and were found to be biologically associated with protein modification and protein location processes. Higher expression of DarkRed genes was associated with higher risk of suffering a relapse and early appearance of relapse (p = 0.045). Our findings suggest that a dysregulation of the TCF4 network could be an important step in the biological process that leads to relapse and suggest that genes related to the ubiquitin proteosome system could be potential biomarkers of relapse.

The usefulness of Olanzapine plasma concentrations in monitoring treatment efficacy and metabolic disturbances in first-episode psychosis.

INTRODUCTION: The role of Olanzapine therapeutic drug monitoring is controversial. The present study explores the associations of Olanzapine plasma concentrations with clinical response and metabolic side effects in first episode psychosis (FEP) after 2 months of treatment. METHODS: Forty-seven patients were included. Improvement in clinical symptomatology was assessed using the PANSS. Metabolic assessment included weight, blood pressure, waist circumference, blood glucose, total cholesterol, high-density lipoprotein, low-density lipoprotein, and triglycerides. RESULTS: The Olanzapine plasma concentrations after 2 months of treatment were positively correlated with weight gain (r = 0.49, p = 0.003), and a concentration > 23.28 ng/mL was identified as a positive predictor of weight gain (≥ 7%). The Olanzapine concentration to dose (C/D) ratio was positively correlated with the percentage of improvement in the total PANSS (r = 0.46, p = 0.004), and a C/D ratio > 2.12 was identified as a positive predictor of a good response (percentage of improvement > 30%) after 2 months of treatment. We also identified several factors that could alter Olanzapine pharmacokinetics: gender (p = 0.03), diagnosis (p = 0.05), smoking habit (p = 0.05), and co-medications such as valproic acid (p = 0.05) and anxiolytics (p = 0.01). DISCUSSION: In conclusion, our results suggest that therapeutic drug monitoring of Olanzapine could be helpful to evaluate therapeutic efficacy and metabolic dysfunction in FEP patients treated with Olanzapine.

Primer ensayo clínico empleando la estimulación cerebral profunda en pacientes con esquizofrenia resistente / Deep brain stimulation in treatment resistant schizophrenia: A pilot randomized cross-over clinical trial

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Personalized medicine begins with the phenotype: identifying antipsychotic response phenotypes in a first-episode psychosis cohort.

AIMS: Here, we present a clustering strategy to identify phenotypes of antipsychotic (AP) response by using longitudinal data from patients presenting first-episode psychosis (FEP). METHOD: One hundred and ninety FEP with complete data were selected from the PEPs project. The efficacy was assessed using total PANSS, and adverse effects using total UKU, during one-year follow-up. We used the Klm3D method to cluster longitudinal data. RESULTS: We identified four clusters: cluster A, drug not toxic and beneficial; cluster B, drug beneficial but toxic; cluster C, drug neither toxic nor beneficial; and cluster D, drug toxic and not beneficial. These groups significantly differ in baseline demographics, clinical, and neuropsychological characteristics (PAS, total PANSS, DUP, insight, pIQ, age of onset, cocaine use and family history of mental illness). CONCLUSIONS: The results presented here allow the identification of phenotypes of AP response that differ in well-known simple and classic clinical variables opening the door to clinical prediction and application of personalized medicine.

Influence of social cognition as a mediator between cognitive reserve and psychosocial functioning in patients with first episode psychosis.

BACKGROUND: Social cognition has been associated with functional outcome in patients with first episode psychosis (FEP). Social cognition has also been associated with neurocognition and cognitive reserve. Although cognitive reserve, neurocognitive functioning, social cognition, and functional outcome are related, the direction of their associations is not clear. Therefore, the main aim of this study was to analyze the influence of social cognition as a mediator between cognitive reserve and cognitive domains on functioning in FEP both at baseline and at 2 years. METHODS: The sample of the study was composed of 282 FEP patients followed up for 2 years. To analyze whether social cognition mediates the influence of cognitive reserve and cognitive domains on functioning, a path analysis was performed. The statistical significance of any mediation effects was evaluated by bootstrap analysis. RESULTS: At baseline, as neither cognitive reserve nor the cognitive domains studied were related to functioning, the conditions for mediation were not satisfied. Nevertheless, at 2 years of follow-up, social cognition acted as a mediator between cognitive reserve and functioning. Likewise, social cognition was a mediator between verbal memory and functional outcome. The results of the bootstrap analysis confirmed these significant mediations (95% bootstrapped CI (-10.215 to -0.337) and (-4.731 to -0.605) respectively). CONCLUSIONS: Cognitive reserve and neurocognition are related to functioning, and social cognition mediates in this relationship.

Widespread Increased Diffusivity Reveals Early Cortical Degeneration in Huntington Disease.

BACKGROUND AND PURPOSE: Huntington disease is a devastating genetic neurodegenerative disorder for which no effective treatment is yet available. Although progressive striatal atrophy is its pathologic hallmark, concomitant cortical deterioration is assumed to occur, but it is poorly characterized. Our objective was to study the loss of cortical integrity and its association with clinical indicators throughout the course of the disease. MATERIALS AND METHODS: Using a cohort of 39 patients with Huntington disease and 25 controls with available MR imaging (T1WI and DTI), we compared cortical atrophy and intracortical diffusivity across disease stages. Intracortical diffusivity is a DTI-derived metric that has recently been suggested to detect incipient neuronal death because water can diffuse more freely in cortical regions with reduced neural density. RESULTS: We observed progressive thinning and increasing diffusivity within the cerebral cortex of patients with Huntington disease (P < .05, corrected for multiple comparisons). Most important, in the absence of pronounced atrophy, widespread increased diffusivity was already present in individuals with premanifest Huntington disease, correlating, in turn, with clinical and disease-specific progression markers. CONCLUSIONS: Intracortical diffusivity may be more sensitive than cortical thinning for tracking early neurodegeneration in Huntington disease. Moreover, our findings provide further evidence of an early cortical compromise in Huntington disease, which contributes to our understanding of its clinical phenotype and could have important therapeutic implications.

Cognitive reserve as an outcome predictor: first-episode affective versus non-affective psychosis.

OBJECTIVE: Cognitive reserve (CR) refers to the brain's capacity to cope with pathology in order to minimize the symptoms. CR is associated with different outcomes in severe mental illness. This study aimed to analyze the impact of CR according to the diagnosis of first-episode affective or non-affective psychosis (FEP). METHOD: A total of 247 FEP patients (211 non-affective and 36 affective) and 205 healthy controls were enrolled. To assess CR, common proxies have been integrated (premorbid IQ; education-occupation; leisure activities). The groups were divided into high and low CR. RESULTS: In non-affective patients, those with high CR were older, had higher socioeconomic status (SES), shorter duration of untreated psychosis, and a later age of onset. They also showed greater performance in most cognitive domains. In affective patients, those with a greater CR showed a higher SES, better functioning, and greater verbal memory performance. CONCLUSION: CR plays a differential role in the outcome of psychoses according to the diagnosis. Specifically, in order to address the needs of non-affective patients with low CR, cognitive rehabilitation treatments will need to be 'enriched' by adding pro-cognitive pharmacological agents or using more sophisticated approaches. However, a functional remediation therapy may be of choice for those with an affective psychosis and low CR.

Affective versus non-affective first episode psychoses: A longitudinal study.

OBJECTIVE: This study aimed to assess (1) whether there were clinical, neuropsychological and functional differences between and within affective and non-affective psychoses at baseline and two years-follow-up and (2) to explore clinical and neuropsychological predictors of psychosocial functioning in the whole sample. METHOD: This is a subanalysis from a multicentre, naturalistic, longitudinal prospective study ('Phenotype-genotype and environmental interaction. Application of a predictive model in first psychotic episodes'). The sample consisted of 192 patients with a first psychotic episode (FEP): 142 with non-affective psychoses and 50 with affective psychoses. Student t-tests, paired t-tests, Pearson correlations, ANOVAs and regression analyses were performed. RESULTS: At baseline, the groups differed in perseverative errors (WCST), Premorbid Adjustment Scale (PAS), family history of psychiatric disorder, negative (PANSS) and manic symptoms (YMRS). At two years follow-up, the groups differed in all the PANSS subscales and in depressive symptoms assessed by the MADRS. When the whole sample was considered, the regression model which best explained the estimated variance in functioning at follow-up (41%) was composed by PANSS total score and verbal fluency assessed by the FAS (COWAT). CONCLUSIONS: We found clinical and neurocognitive differences at baseline which decreased in the follow-up. Reduced performances at baseline in executive functions in combination with symptom severity (PANSS) were predictors of FEP patients' poor functional outcome.

Individual trajectories of cognitive performance in first episode psychosis: a 2-year follow-up study.

Individual changes over time in cognition in patients with psychotic disorders have been studied very little, especially in the case of first episode psychosis (FEP). We aimed to establish whether change in individual trajectories in cognition over 2 years of a sample of 159 FEP patients was reliable and clinically significant, using the reliable change index (RCI) and clinically significant change (CSC) methods. We also studied a sample of 151 matched healthy controls. Patients and controls were assessed with a set of neuropsychological tests, as well as premorbid, clinical and functionality measures. We analysed the course of cognitive measures over time, using analysis of variance, and the individual trajectories in the cognitive measures with the regression-based RCI (RCISRB) and the CSC. The RCISRB showed that between 5.4 and 31.2% of the patients showed deterioration patterns, and between 0.6 and 8.8% showed improvement patterns in these tests over time. Patients showing better cognitive profiles according to RCISRB (worsening in zero to two cognitive measures) showed better premorbid, clinical and functional profiles than patients showing deterioration patterns in more than three tests. When combining RCISRB and CSC values, we found that less than 10% of patients showed improvement or deterioration patterns in executive function and attention measures. These results support the view that cognitive impairments are stable over the first 2 years of illness, but also that the analysis of individual trajectories could help to identify a subgroup of patients with particular phenotypes, who may require specific interventions.

Volumetric and morphological characteristics of the hippocampus are associated with progression to schizophrenia in patients with first-episode psychosis.

BACKGROUND: Abnormalities in the hippocampus have been implicated in the pathophysiology of psychosis. However, it is still unclear whether certain abnormalities are a pre-existing vulnerability factor, a sign of disease progression or a consequence of environmental factors. We hypothesized that first-episode psychosis patients who progress to schizophrenia after one year of follow up will display greater volumetric and morphological changes from the very beginning of the disorder. METHODS: We studied the hippocampus of 41 patients with a first-episode psychosis and 41 matched healthy controls. MRI was performed at the time of the inclusion in the study. After one year, the whole sample was reevaluated and divided in two groups depending on the diagnoses (schizophrenia vs. non-schizophrenia). RESULTS: Patients who progressed to schizophrenia showed a significantly smaller left hippocampus volume than control group and no-schizophrenia group (F=3.54; df=2, 77; P=0.03). We also found significant differences in the morphology of the anterior hippocampus (CA1) of patients with first-episode psychosis who developed schizophrenia compared with patients who did not. CONCLUSIONS: These results are consistent with the assumption of hyperfunctioning dopaminergic cortico-subcortical circuits in schizophrenia, which might be related with an alteration of subcortical structures, such as the hippocampus, along the course of the disease. According with these results, hippocampus abnormalities may serve as a prognostic marker of clinical outcome in patients with a first-episode psychosis.

Randomized control trial to assess the efficacy of metacognitive training compared with a psycho-educational group in people with a recent-onset psychosis.

BACKGROUND: Aims were to assess the efficacy of metacognitive training (MCT) in people with a recent onset of psychosis in terms of symptoms as a primary outcome and metacognitive variables as a secondary outcome. METHOD: A multicenter, randomized, controlled clinical trial was performed. A total of 126 patients were randomized to an MCT or a psycho-educational intervention with cognitive-behavioral elements. The sample was composed of people with a recent onset of psychosis, recruited from nine public centers in Spain. The treatment consisted of eight weekly sessions for both groups. Patients were assessed at three time-points: baseline, post-treatment, and at 6 months follow-up. The evaluator was blinded to the condition of the patient. Symptoms were assessed with the PANSS and metacognition was assessed with a battery of questionnaires of cognitive biases and social cognition. RESULTS: Both MCT and psycho-educational groups had improved symptoms post-treatment and at follow-up, with greater improvements in the MCT group. The MCT group was superior to the psycho-educational group on the Beck Cognitive Insight Scale (BCIS) total (p = 0.026) and self-certainty (p = 0.035) and dependence self-subscale of irrational beliefs, comparing baseline and post-treatment. Moreover, comparing baseline and follow-up, the MCT group was better than the psycho-educational group in self-reflectiveness on the BCIS (p = 0.047), total BCIS (p = 0.045), and intolerance to frustration (p = 0.014). Jumping to Conclusions (JTC) improved more in the MCT group than the psycho-educational group (p = 0.021). Regarding the comparison within each group, Theory of Mind (ToM), Personalizing Bias, and other subscales of irrational beliefs improved in the MCT group but not the psycho-educational group (p < 0.001-0.032). CONCLUSIONS: MCT could be an effective psychological intervention for people with recent onset of psychosis in order to improve cognitive insight, JTC, and tolerance to frustration. It seems that MCT could be useful to improve symptoms, ToM, and personalizing bias.

Association of the brain-derived neurotrophic factor Val66Met polymorphism with negative symptoms severity, but not cognitive function, in first-episode schizophrenia spectrum disorders.

OBJECTIVE: A functional polymorphism of the brain-derived neurotrophic factor gene (BDNF) Val66Met has been associated with cognitive function and symptom severity in patients with schizophrenia. It has been suggested that the Val66Met polymorphism has a role as a modulator in a range of clinical features of the illness, including symptoms severity, therapeutic responsiveness, age of onset, brain morphology and cognitive function. However, little work has been done in first-episode schizophrenia (FES) spectrum disorders. The objective of this study is to investigate the association of the BDNF Val66Met polymorphism on cognitive function and clinical symptomatology in FES patients. METHODS: Using a cross-sectional design in a cohort of 204 patients with FES or a schizophrenia spectrum disorder and 204 healthy matched controls, we performed BDNF Val66Met genotyping and tested its relationship with cognitive testing (attention, working memory, learning/verbal memory and reasoning/problem-solving) and assessment of clinical symptom severity. RESULTS: There was no significant influence of the BDNF allele frequency on cognitive factor scores in either patients or controls. An augmented severity of negative symptoms was found in FES patients that carried the Met allele. CONCLUSIONS: The results of this study suggest that in patients with a first-episode of schizophrenia or a schizophrenia spectrum disorder, the BDNF Val66Met polymorphism does not exert an influence on cognitive functioning, but is associated with negative symptoms severity. BDNF may serve as suitable marker of negative symptomatology severity in FES patients within the schizophrenia spectrum.

Pharmacogenetic study of antipsychotic induced acute extrapyramidal symptoms in a first episode psychosis cohort: role of dopamine, serotonin and glutamate candidate genes.

This study investigated whether the risk of presenting antipsychotic (AP)-induced extrapyramidal symptoms (EPS) could be related to single-nucleotide polymorphisms (SNPs) in a naturalistic cohort of first episode psychosis (FEP) patients. Two hundred and two SNPs in 31 candidate genes (involved in dopamine, serotonin and glutamate pathways) were analyzed in the present study. One hundred and thirteen FEP patients (43 presenting EPS and 70 non-presenting EPS) treated with high-potency AP (amisulpride, paliperidone, risperidone and ziprasidone) were included in the analysis. The statistical analysis was adjusted by age, gender, AP dosage, AP combinations and concomitant treatments as covariates. Four SNPs in different genes (DRD2, SLC18A2, HTR2A and GRIK3) contributed significantly to the risk of EPS after correction for multiple testing (P<1 × 10(-4)). These findings support the involvement of dopamine, serotonin and glutamate pathways in AP-induced EPS.

Estimulación cerebral profunda (DBS) en la esquizofrenia resistente / Clinical improvement in a treatment-resistant patient with schizophrenia treated with deep brain stimulation

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Guía de la Sociedad Española de Infectología Pediátrica para el diagnóstico y tratamiento de la toxoplasmosis congénita / The Spanish Society of Pediatric Infectious Diseases Guidelines for the diagnosis and treatment of congenital toxoplasmosis

La toxoplasmosis congénita es la consecuencia de la transmisión fetal por vía transplacentaria de Toxoplasma gondii tras la primoinfección materna. El riesgo de infección fetal es bajo en infecciones en el primer trimestre y va aumentando con la edad gestacional, mientras que la gravedad de la infección disminuye con esta. El diagnóstico de infección materna se realiza mediante la demostración de seroconversión o ante la presencia de IgM positiva con anticuerpos IgG de baja avidez. Las gestantes con infección demostrada deben recibir espiramicina para intentar evitar su transmisión al feto. El diagnóstico de infección fetal se realiza mediante reacción en cadena de la polimerasa (PCR) en líquido amniótico obtenido a partir de la semana 18 de gestación. Si esta prueba resulta positiva, debe iniciarse tratamiento a la embarazada con pirimetamina, sulfadiazina y ácido folínico. La mayoría de los niños infectados nacen asintomáticos pero hasta el 80% desarrolla secuelas visuales o neurológicas durante su infancia y adolescencia. El diagnóstico neonatal es complicado porque los anticuerpos IgM e IgA y la PCR en sangre y líquido cefalorraquídeo pueden ser falsamente negativos. En estos casos, el diagnóstico puede realizarse mediante la constatación de un ascenso significativo de los anticuerpos IgG o la persistencia de los mismos después del año de vida. El tratamiento neonatal con pirimetamina y sulfadiazina disminuye la posibilidad de secuelas a largo plazo. La toxoplasmosis congénita es una enfermedad prevenible mediante el cribado pregestacional y la adopción de medidas de profilaxis primaria en las gestantes seronegativas (AU)

Congenital toxoplasmosis is the result of transplacental fetal infection by Toxoplasma gondii after the primary maternal infection. The severity of the disease depends on the gestational age at transmission. First trimester infections are more severe, but less frequent, than third trimester infections. Acute maternal infection is diagnosed by seroconversion or by the detection of IgM antibodies and a low IgG avidity test. In these cases, spiramycin should be initiated to prevent transmission to the fetus. For identification of fetal infection, polymerase chain reaction (PCR) testing of amniotic fluid after 18 weeks gestation should be performed. If fetal infection is confirmed, the mothers should be treated with pyrimethamine, sulfadiazine and folinic acid. Most infants infected in utero are born with no obvious signs of toxoplasmosis, but up to 80% developed learning and visual disabilities later in life. Neonatal diagnosis with IgM/IgA antibodies or blood/cerebrospinal fluid PCR may be difficult because false-negative results frequently occur. In these cases diagnosis is possible by demonstrating a rise in IgG titers during follow-up or by the detection of antibodies beyond one year of age. Early treatment with pyrimethamine and sulfadiazine may improve the ophthalmologic and neurological outcome. Congenital toxoplasmosis is a preventable disease. Pre-pregnancy screening and appropriate counseling regarding prevention measures in seronegative women may prevent fetal infection (AU)

[The Spanish Society of Pediatric Infectious Diseases Guidelines for the diagnosis and treatment of congenital toxoplasmosis]. / Guía de la Sociedad Española de Infectología Pediátrica para el diagnóstico y tratamiento de la toxoplasmosis congénita.

Congenital toxoplasmosis is the result of transplacental fetal infection by Toxoplasma gondii after the primary maternal infection. The severity of the disease depends on the gestational age at transmission. First trimester infections are more severe, but less frequent, than third trimester infections. Acute maternal infection is diagnosed by seroconversion or by the detection of IgM antibodies and a low IgG avidity test. In these cases, spiramycin should be initiated to prevent transmission to the fetus. For identification of fetal infection, polymerase chain reaction (PCR) testing of amniotic fluid after 18 weeks gestation should be performed. If fetal infection is confirmed, the mothers should be treated with pyrimethamine, sulfadiazine and folinic acid. Most infants infected in utero are born with no obvious signs of toxoplasmosis, but up to 80% developed learning and visual disabilities later in life. Neonatal diagnosis with IgM/IgA antibodies or blood/cerebrospinal fluid PCR may be difficult because false-negative results frequently occur. In these cases diagnosis is possible by demonstrating a rise in IgG titers during follow-up or by the detection of antibodies beyond one year of age. Early treatment with pyrimethamine and sulfadiazine may improve the ophthalmologic and neurological outcome. Congenital toxoplasmosis is a preventable disease. Pre-pregnancy screening and appropriate counseling regarding prevention measures in seronegative women may prevent fetal infection.

Clinical and serotonergic predictors of non-affective acute remitting psychosis in patients with a first-episode psychosis.

OBJECTIVE: The study aimed to establish clinical predictors of non-affective acute remitting psychosis (NARP) and assess whether these patients showed a distinct serotonergic profile. METHOD: First-episode never treated psychotic patients diagnosed of paranoid schizophrenia (n=35; 21 men and 14 women) or NARP (n=28; 15 men and 13 women) were included. RESULTS: NARP patients showed significantly lower negative symptomatology, better premorbid adjustment, shorter duration of untreated psychosis, more depressive symptomatology and a lower number of 5-HT2A receptors than the paranoid schizophrenia patients. In the logistic regression, the four variables associated with the presence of NARP were: low number of 5-HT2A receptors; good premorbid adjustment; low score in the item 'hallucinatory behaviour' and reduced duration of untreated psychosis. CONCLUSION: Our findings support the view that NARP is a highly distinctive condition different from either affective psychosis or other non-affective psychosis such as schizophrenia, and highlight the need for its validation.

Pharmacokinetics and time-course of D(2) receptor occupancy induced by atypical antipsychotics in stabilized schizophrenic patients.

The (123)I-IBZM SPECT measured D(2) receptor occupancy (D(2)RO) in chronically dosed, stabilized schizophrenic patients and its relationship with antipsychotic (AP) pharmacokinetics (PK) over time is still unclear. The aims of this study were: 1) To define the relationship between striatal D(2) receptor occupancy (D( 2)RO) and plasma concentration (C(P)) in stabilized schizophrenic patients on clinically relevant doses using (123)I-IBZM SPECT; 2) To investigate the time course of AP-induced D(2)RO and corresponding C(P). Forty-six schizophrenic patients on their clinically required doses of risperidone, olanzapine, clozapine or quetiapine were included. D( 2)RO and C(P) were measured over time following a sparse-sampling experimental design, and individual PK and D(2)RO-time profiles were estimated using a population approach. Observed striatal D(2)RO and C(P) ranges were 28-75% and 9.4-60.5 ng/mL for risperidone, 22-84% and 8.6-89.5 ng/mL for olanzapine, 5-53% and 41.6-818.2 ng/mL for clozapine and 0-64% and 37.9-719.6 ng/mL for quetiapine. A PK-D(2)RO relationship was found for the four APs. D(2)RO pattern over time was stable for risperidone, olanzapine and clozapine but fluctuating for quetiapine. Stabilized schizophrenic patients show a wide range of both D(2)RO and C(P) at clinically effective doses of the four AP, suggesting that clinical response to these AP may be maintained with D(2)RO below 65%. D(2)RO patterns over time differ between AP. These results should be considered for accurate interpretation of D(2)RO measurements, proper design of studies and optimization of drug regimens for patients on AP treatment.