Increased brain serotonin turnover in panic disorder patients in the absence of a panic attack: reduction by a selective serotonin reuptake inhibitor

Since the brain neurotransmitter changes characterising panic disorder remain uncertain, we quantified brain noradrenaline and serotonin turnover in patients with panic disorder, in the absence of a panic attack. Thirty-four untreated patients with panic disorder and 24 matched healthy volunteers were studied. A novel method utilising internal jugular venous sampling, with thermodilution measurement of jugular blood flow, was used to directly quantify brain monoamine turnover, by measuring the overflow of noradrenaline and serotonin metabolites from the brain. Radiographic depiction of brain venous sinuses allowed differential venous sampling from cortical and subcortical regions. The relation of brain serotonin turnover to serotonin transporter genotype and panic disorder severity were evaluated, and the influence of an SSRI drug, citalopram, on serotonin turnover investigated. Brain noradrenaline turnover in panic disorder patients was similar to that in healthy subjects. In contrast, brain serotonin turnover, estimated from jugular venous overflow of the metabolite, 5-hydroxyindole acetic acid, was increased approximately 4-fold in subcortical brain regions and in the cerebral cortex (P < 0.01). Serotonin turnover was highest in patients with the most severe disease, was unrelated to serotonin transporter genotype, and was reduced by citalopram (P < 0.01). Normal brain noradrenaline turnover in panic disorder patients argues against primary importance of the locus coeruleus in this condition. The marked increase in serotonin turnover, in the absence of a panic attack, possibly represents an important underlying neurotransmitter substrate for the disorder, although this point remains uncertain. Support for this interpretation comes from the direct relationship which existed between serotonin turnover and illness severity, and the finding that SSRI administration reduced serotonin turnover. Serotonin transporter genotyping suggested that increased whole brain serotonin turnover most likely derived not from impaired serotonin reuptake, but from increased firing in serotonergic midbrain raphe neurons projecting to both subcortical brain regions and the cerebral cortex.     

Knowledge of one's kinematics improves perceptual discrimination

We tested the hypothesis that our ability to detect fine kinematics variations is tuned to reveal more subtle differences when the motion pattern belongs to the observer compared to another individual. To this purpose, we analyzed the responses of 15 subjects in a same-different task on pairs of movements, which could belong to one or two different subjects. Self vs. Other comparisons were obtained by presenting both the observer's and another participant's kinematics. Subjects responded faster and more accurately when they observed their own gestures compared to movements of another participant. In the latter case, slight kinematic differences were more likely to remain undetected. These findings are discussed within an ecological framework: in observing others, we are more concerned with detection of goals and intentions, i.e., outstanding variations in motion patterns. Conversely, in self-observation detection of more subtle differences is required to facilitate learning and optimization of motor acts.     

A class of multidimensional IRT models for testing unidimensionality and clustering items

We illustrate a class of multidimensional item response theory models in which the items are allowed to have different discriminating power and the latent traits are represented through a vector having a discrete distribution. We also show how the hypothesis of unidimensionality may be tested against a specific bidimensional alternative by using a likelihood ratio statistic between two nested models in this class. For this aim, we also derive an asymptotically equivalent Wald test statistic which is faster to compute. Moreover, we propose a hierarchical clustering algorithm which can be used, when the dimensionality of the latent structure is completely unknown, for dividing items into groups referred to different latent traits. The approach is illustrated through a simulation study and an application to a dataset collected within the National Assessment of Educational Progress, 1996. The author would like to thank the Editor, an Associate Editor and three anonymous referees for stimulating comments. I also thank L. Scaccia, F. Pennoni and M. Lupparelli for having done part of the simulations.     

Interaction of Combat Exposure and Unit Cohesion in Predicting Suicide‐Related Ideation Among Post‐Deployment Soldiers

Suicide is one of the leading causes of death among U.S. Army soldiers. Suicide‐related ideation, which is associated with suicide attempts and suicide, can cause considerable distress. In a sample of 1,663 recently redeployed soldiers, we used factor analysis and structural equation modeling to test the associations between combat exposure, unit cohesion, and their interaction in predicting suicide‐related ideation. We found that combat exposure was a significant risk factor for suicide‐related ideation, while unit cohesion was a significant protective factor. The significant interaction between the two factors indicated that soldiers who experienced greater combat exposure but also had higher levels of unit cohesion had relatively lower levels of suicide‐related ideation. In addition, those who had higher levels of combat exposure and lower unit cohesion were most at risk for suicide‐related ideation. Our findings indicate the importance of unit cohesion in protecting soldiers from suicide‐related ideation and suggest a higher risk group of soldiers who should be targeted for interventions.     

Mood,Anxiety, and Substance‐Use Disorders and Suicide Risk in a Military Population Cohort

There are meager prospective data from nonclinical samples on the link between anxiety disorders and suicide or the extent to which the association varies over time. We examined these issues in a cohort of 309,861 U.S. Air Force service members, with 227 suicides over follow‐up. Mental disorder diagnoses including anxiety, mood, and substance‐use disorders (SUD) were based on treatment encounters. Risk for suicide associated with anxiety disorders were lower compared with mood disorders and similar to SUD. Moreover, the associations between mood and anxiety disorders with suicide were greatest within a year of treatment presentation.     

Characteristics of a French African Caribbean Epidemiological Psychiatric Sample with a History of Suicide Attempt

Research on vulnerability factors among ethnic groups, independent of primary psychiatric diagnosis, may help to identify groups at risk of suicidal behavior. French African Caribbean general psychiatric patients (N = 362) were recruited consecutively and independently of the primary psychiatric diagnosis. Demographic and clinical characteristics and lifetime history of suicide attempts were recorded. Sixty‐five patients (18%) had a history of at least one suicide attempt. Presence of professional qualifications, children, poor social contacts, treatment with benzodiazepine at inclusion, and poor treatment compliance were all associated with a lifetime history of suicide attempts.     

Do Geographic Regions with Higher Suicide Rates also have Higher Rates of Nonfatal Intentional Self‐Harm?

Fatal and nonfatal intentional self‐harm events in eight U.S. states were compared using emergency department, hospital, and vital statistics data. Nonfatal event rates increased by an estimated 24.20% over 6 years. Case fatality ratios varied widely, but two northeastern states' total event rates (fatal plus nonfatal) were very high (New Hampshire 206.5/100,000 person years; Massachusetts 166.7/100,000). Geographic context did not uniformly impact the likelihood of self‐harm across event types. The state‐level public health burden posed by such acts cannot, therefore, be accurately estimated from either mortality or morbidity data alone.     

The Beliefs in the Inheritance of Risk Factors for Suicide Scale (BIRFSS): Cross‐Cultural Validation in Estonia,Malaysia, Romania,the United Kingdom,and the United States

The genetics of suicide is increasingly recognized and relevant for mental health literacy, but actual beliefs may lag behind current knowledge. We examined such beliefs in student samples (total N = 686) from Estonia, Malaysia, Romania, the United Kingdom, and the United States with the Beliefs in the Inheritance of Risk Factors for Suicide Scale. Cultural effects were small, those of key demographics nil. Several facets of construct validity were demonstrated. Marked differences in perceived plausibility of evidence about the genetics of suicide according to research design, observed in all samples, may be of general interest for investigating lay theories of abnormal behavior and communicating behavioral and psychiatric genetic research findings.