Schizophrenia is characterized by increased behavioral and neurochemical responses to dopamine-releasing drugs. This prompted the hypothesis of psychosis as a state of "endogenous" sensitization of the dopamine system although the exact basis of dopaminergic disturbances and the possible role of prefrontal cortical regulation have remained uncertain. To show that patients with first-episode psychosis release more dopamine upon amphetamine-stimulation than healthy volunteers, and to reveal for the first time that prospective sensitization induced by repeated amphetamine exposure increases dopamine-release in stimulant-naïve healthy volunteers to levels observed in patients, we collected data on amphetamine-induced dopamine release using the dopamine D 2/3 receptor agonist radioligand [ 11 C]-(+)-PHNO and positron emission tomography. Healthy volunteers (n = 28, 14 female) underwent a baseline and then a post-amphetamine scan before and after a mildly sensitizing regimen of repeated oral amphetamine. Unmedicated patients with first-episode psychosis (n = 21; 6 female) underwent a single pair of baseline and then post-amphetamine scans. Furthermore, T1 weighted magnetic resonance imaging of the prefrontal cortex was performed. Patients with first-episode psychosis showed larger release of dopamine compared to healthy volunteers. After sensitization of healthy volunteers their dopamine release was significantly amplified and no longer different from that seen in patients. Healthy volunteers showed a negative correlation between prefrontal cortical volume and dopamine release. There was no such relationship after sensitization or in patients. Our data in patients with untreated first-episode psychosis confirm the "endogenous sensitization" hypothesis and support the notion of impaired prefrontal control of the dopamine system in schizophrenia.

Introduction Due to favorable antidepressant (AD) efficacy and tolerability, selective-serotonin reuptake inhibitors (SSRIs) are consistently recommended as substances of first choice for the treatment of major depressive disorder (MDD) in international guidelines. However, little is known about the real-world clinical correlates of patients primarily prescribed SSRIs in contrast to those receiving alternative first-line ADs. Methods These secondary analyses are based on a naturalistic, multinational cross-sectional study conducted by the European Group for the Study of Resistant Depression at ten research sites. We compared the socio-demographic and clinical characteristics of 1410 patients with primary MDD, who were either prescribed SSRIs or alternative substances as first-line AD treatment, using chi-squared tests, analyses of covariance, and logistic regression analyses. Results SSRIs were prescribed in 52.1% of MDD patients who showed lower odds for unemployment, current severity of depressive symptoms, melancholic features, suicidality, as well as current inpatient treatment compared to patients receiving alternative first-line ADs. Furthermore, patients prescribed SSRIs less likely received add-on therapies including AD combination and augmentation with antipsychotics, and exhibited a trend towards higher response rates. Conclusion A more favorable socio-demographic and clinical profile associated with SSRIs in contrast to alternative first-line ADs may have guided European psychiatrists’ treatment choice for SSRIs, rather than any relevant pharmacological differences in mechanisms of action of the investigated ADs. Our results must be cautiously interpreted in light of predictable biases resulting from the open treatment selection, the possible allocation of less severely ill patients to SSRIs as well as the cross-sectional study design that does not allow to ascertain any causal conclusions.

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Highlights Disturbed glycemic control is an intrinsic feature of schizophrenia. The neurotransmitter dopamine has a key role in regulating glucose homeostasis. We studied brain dopamine and blood glucose levels in first episode psychosis. The relationship between glucose and brain dopamine is altered in schizophrenia.