A new nosology of psychosis and the pharmacological basis of affective and negative symptom dimensions in schizophrenia

The serotonin transporter gene 5-HTTLPR polymorphism is associated with affective psychoses but not with schizophrenia: A large-scale study in the Russian population

BACKGROUND

Affective syndrome is thought to be a key feature that differentiates schizophrenia from schizoaffective disorder (SA) and bipolar disorder with psychotic features (BDP). However genetic underpinnings of these differences remain unresolved.

OBJECTIVES

We compared clinical variables of affective psychoses (SA, BDP and schizophrenia with affective symptoms (AFF SCZ)) and schizophrenia without affective symptoms (non-AFF SCZ) and searched for a genetic variant that may differentiate affective psychosis from non-AFF SCZ.

METHODS

A total of 2677 subjects, including 831 patients with affective psychosis, 785 patients with non-AFF SCZ and 1061 healthy controls, were used. Clinical symptoms were assessed with the PANSS. The sample was genotyped for 5-HTTLPR polymorphism of the serotonin transporter gene.

RESULTS

The diagnostic groups differed significantly on demographic and clinical variables. The percentage of men was higher, the current age and age at illness onset were lower in non-AFF SCZ and SA compared to AFF SCZ and BDP. The severity of positive and negative symptoms decreased significantly from group to group in the following manner: non-AFF SCZ>AFF SCZ>SA>BDP. There was the association between 5-HTTLPR polymorphism and affective psychosis (p=0.01). The frequency of the SS genotype was higher in the affective psychosis group compared to non-AFF SCZ and controls. No differences in the genotype distribution were identified between the non-AFF SCZ group and controls.

LIMITATIONS

Difficulties in the differentiation between non-AFF SCZ and AFF SCZ or SA and between AFF SCZ and SA due to uncertain diagnostic boundaries between these conditions.

CONCLUSIONS

SA is intermediate between non-AFF SCZ and BDP in the severity of positive and negative symptoms. The first episode patients, carriers of the SS genotype have a higher risk of developing affective psychosis than non-AFF SCZ. This finding carries implications for the prognosis of psychosis outcomes in the first-episode patients.

The effect of deficient muscarinic signaling on commonly reported biochemical effects in schizophrenia and convergence with genetic susceptibility loci in explaining symptom dimensions of psychosis

With the advent of DSM 5 criticism has generally centered on a lack of biological validity of the diagnostic criteria. Part of the problem in describing a nosology of psychosis is the tacit assumption of multiple genetic causes each with an incremental loading on the clinical picture that fails to differentiate a clear underlying pathophysiology of high impact. The aim of this paper is to consolidate a primary theory of deficient muscarinic signaling underlying key clinical features of schizophrenia and its regulation by several important genetic associations including neuregulin, DISC and dysbindin. Secondary reductions in markers for GABAergic function and changes in the levels of interneuron calcium binding proteins parvalbumin and calbindin can be attributed to dysfunctional muscarinic transduction. A parallel association exists for cytokine production. The convergent pathway hypothesis is likewise used to model dopaminergic and glutamatergic theories of schizophrenia. The negative symptom dimension is correlated with dysfunction of Akt and ERK transduction, a major point of convergence. The present paradigm predicts the importance of a recent finding of a deletion in a copy number variant of PLCB1 and its potential use if replicated, as one of the first testable biological markers differentiating schizophrenia from bipolar disorder and further subtyping of schizophrenia into deficit and non-deficit. Potential limitations of PLCB1 as a prospective marker are also discussed.

Attentional and emotional functioning in schizophrenia patients treated with conventional and atypical antipsychotic drugs

BACKGROUND

Effectiveness of antipsychotics in treating emotional and cognitive deficits in schizophrenia still remains controversial. The aim of our study was to assess emotional and cognitive functioning in schizophrenic inpatients currently treated with typical antipsychotics (perphenazine, perazine, fluphenazine, and haloperidol) and in another group of schizophrenic inpatients currently on atypical antipsychotics (olanzapine, risperidone, amisulpride, and quetiapine).

MATERIAL/METHODS

One hundred patients with DSM-IV schizophrenia or schizoaffective disorders (39 treated using typical antipsychotics and 61 treated with atypical antipsychotics) under naturalistic treatment conditions, and 50 healthy controls were given the following: Test of Everyday Attention, Facial Emotion Recognition Test, Facial Memory Recognition Test, and "Reading the mind in the eyes" Test.

RESULTS

Patients with a diagnosis of schizophrenia revealed the following deficits: facial emotion perception, empathy /theory of mind, visual selective attention/speed, attentional switching, and auditory-verbal working memory. Our results show a significant difference between schizophrenic and healthy controls in all tasks, with schizophrenic patients performing worse than controls. Interestingly, our patients on atypical neuroleptics performed similarly compared to schizophrenic patients treated with conventional neuroleptics on all tasks provided. There were some significant relationships between emotional and cognitive deficits and clinical variables.

CONCLUSIONS

Our findings remain consistent with other recent studies in which atypical antipsychotics did not show a clear advantage over typical antipsychotics on both emotional and cognitive functioning.