No evidence for physical anhedonia as a candidate symptom or an endophenotype in bipolar affective disorder

Mapping inflammation onto mood: Inflammatory mediators of anhedonia

Evidence supports inflammatory involvement in mood and cognitive symptoms across psychiatric, neurological and medical disorders; however, inflammation is not a sensitive or specific characteristic of these diagnoses. The National Institute of Mental Health Research Domain Criteria (RDoC) ask for a shift away from symptom-based diagnoses toward a transdiagnostic neurobiological focus in the study of brain illnesses. The RDoC matrix may provide a useful framework for integrating the effects of inflammation on brain function. Based on preclinical and clinical findings, relevant relationships span negative and positive valence systems, cognitive systems, systems for social processes and arousal/regulatory systems. As an exemplar, we consider the psychopathological domain of anhedonia, conceptualizing the relevance of inflammation (e.g., cellular immunity) and downstream processes (e.g., indoleamine 2,3-dioxygenase activation and oxidative inactivation of tetrahydrobiopterin) across RDoC units of analysis (e.g., catecholamine neurotransmitter molecules, nucleus accumbens medium spiny neuronal cells, dopaminergic mesolimbic and mesocortical reward circuits, animal paradigms, etc.). We discuss implications across illnesses affecting the brain, including infection, major depressive disorder, stroke, Alzheimer's disease and type 2 diabetes.

Schizotypy and clinical symptoms, cognitive function, and quality of life in individuals with a psychotic disorder

BACKGROUND

Schizotypy is a range of perceptual experiences and personality features related to risk and familial predisposition to psychosis. Despite evidence that schizotypy is related to psychosis vulnerability, very little is known about the expression of schizotypal traits in individuals with a psychotic disorder, and their relationship to clinical symptoms, cognition, and psychosocial functioning.

METHODS

59 healthy subjects and 68 patients with a psychotic disorder (47 schizophrenia spectrum disorder; 21 bipolar disorder with psychotic features) completed four schizotypy scales, the Perceptual Aberration Scale, the Revised Physical and Social Anhedonia Scales, and the Schizotypal Personality Questionnaire, a brief neuropsychological assessment, and a self-report measure of quality of life. Clinical symptoms of psychosis were quantified in patients with the Positive and Negative Syndrome Scale (PANSS).

RESULTS

Psychosis patients scored higher than healthy subjects on all schizotypy scales. Correlations between schizotypy and PANSS scores were modest, ranging from r=.06 to r=.43, indicating that less than 20% of the variance in self-reported schizotypy overlapped with clinical symptoms. After controlling for clinical symptoms, patients with schizophrenia spectrum disorders reported higher levels of cognitive-perceptual disturbances and negative traits than patients with bipolar disorder. Elevated schizotypy was associated with lower cognitive functioning and self-reported quality of life.

CONCLUSIONS

Schizotypal personality traits are markedly elevated in psychotic disorders, especially schizophrenia spectrum disorders, relatively weakly correlated with positive and negative psychotic symptoms, and associated with greater cognitive impairment and lower quality of life. Assessing schizotypy in patients with psychosis may be useful for predicting functional outcome and differential diagnosis.

Differential hedonic experience and behavioral activation in schizophrenia and bipolar disorder

The Kraepelinian distinction between schizophrenia (SZ) and bipolar disorder (BP) emphasizes affective and volitional impairment in the former, but data directly comparing the two disorders for hedonic experience are scarce. This study examined whether hedonic experience and behavioral activation may be useful phenotypes distinguishing SZ and BP. Participants were 39 SZ and 24 BP patients without current mood episode matched for demographics and negative affect, along with 36 healthy controls (HC). They completed the Chapman Physical and Social Anhedonia Scales, Temporal Experience of Pleasure Scale (TEPS), and Behavioral Activation Scale (BAS). SZ and BP showed equally elevated levels of self-report negative affect and trait anhedonia compared to HC. However, SZ reported significantly lower pleasure experience (TEPS) and behavioral activation (BAS) than BP, who did not differ from HC. SZ and BP showed differential patterns of relationships between the hedonic experience and behavioral activation measures. Overall, the results suggest that reduced hedonic experience and behavioral activation may be effective phenotypes distinguishing SZ from BP even when affective symptoms are minimal. However, hedonic experience differences between SZ and BP are sensitive to measurement strategy, calling for further research on the nature of anhedonia and its relation to motivation in these disorders.

Anti-anhedonic effect of ketamine and its neural correlates in treatment-resistant bipolar depression

Anhedonia--which is defined as diminished pleasure from, or interest in, previously rewarding activities-is one of two cardinal symptoms of a major depressive episode. However, evidence suggests that standard treatments for depression do little to alleviate the symptoms of anhedonia and may cause reward blunting. Indeed, no therapeutics are currently approved for the treatment of anhedonia. Notably, over half of patients diagnosed with bipolar disorder experience significant levels of anhedonia during a depressive episode. Recent research into novel and rapid-acting therapeutics for depression, particularly the noncompetitive N-Methyl-D-aspartate receptor antagonist ketamine, has highlighted the role of the glutamatergic system in the treatment of depression; however, it is unknown whether ketamine specifically improves anhedonic symptoms. The present study used a randomized, placebo-controlled, double-blind crossover design to examine whether a single ketamine infusion could reduce anhedonia levels in 36 patients with treatment-resistant bipolar depression. The study also used positron emission tomography imaging in a subset of patients to explore the neurobiological mechanisms underpinning ketamine's anti-anhedonic effects. We found that ketamine rapidly reduced the levels of anhedonia. Furthermore, this reduction occurred independently from reductions in general depressive symptoms. Anti-anhedonic effects were specifically related to increased glucose metabolism in the dorsal anterior cingulate cortex and putamen. Our study emphasizes the importance of the glutamatergic system in treatment-refractory bipolar depression, particularly in the treatment of symptoms such as anhedonia.

Anhedonia revisited: is there a role for dopamine-targeting drugs for depression?

It is 16 years since we reviewed anhedonia in depression. Since then, there have been important developments in the study of anhedonia, mainly using the new techniques that neuroimaging made available, which provide very interesting new insights. It is becoming increasingly apparent that anhedonia, with psychomotor retardation, defines a dimension in depressive disorder that seems to be distinct from a dimension encompassing mood plus somatic symptoms. These dimensions can coexist, but may also be present separately. The first appears associated with disturbances (under-functioning) in dopamine function; the other appears to be related to a similar under-functioning in the serotonin system. Furthermore, anhedonia itself increasingly appears to be a composite symptom, consisting of at least two dimensions (i.e. a motivational/appetitive and a consummatory one). Depression appears to be characteristically linked more to the first one, in contrast to what was originally thought. We discuss the significance of the above in the evolving treatment of depression and the potential use of dopamine-targeting drugs.

Reduced hedonic capacity in euthymic bipolar subjects: a trait-like feature?

BACKGROUND

The aim of our study was to assess hedonic capacity in euthymic bipolar subjects, identifying possible differences compared to remitted unipolar depressed patients and healthy controls.

METHODS

107 subjects with bipolar disorders, 86 with major depressive disorder and 106 healthy controls, homogeneous with respect to demographic characteristics, were enrolled. The following scales were administered: the Snaith-Hamilton pleasure scale (SHAPS), the subscale for 'anhedonia/asociality' of the scale for the assessment of negative symptoms (SANS) and the visual analogue scale (VAS) for hedonic capacity.

RESULTS

Scores on SHAPS total, interests and social interactions, SANS 'anhedonia/asociality' and VAS were all significantly higher in affective disorder patients compared to healthy controls. No difference was found between clinical groups. 20.5% (n=22) of bipolar disorder subjects and 24.5% (n=21) of major depressed subjects showed a significant reduction in hedonic capacity (SHAPS total score ≥ 3), compared to 7.5% (n=8) of healthy controls (χ(2)=12.03; p=.002).

LIMITATIONS

Limitations include heterogeneity with respect to pharmacological status and longitudinal course (i.e., 'single' vs. 'recurrent' affective episodes).

CONCLUSIONS

The major finding of our study is that euthymic bipolar patients and remitted major depressed patients display residual anhedonic symptoms. This suggests that, in affective disorder patients, altered hedonic capacity could represent an enduring trait and that, possibly, dysfunctions in the neurobiological mechanisms underlying hedonic response and reward processing persist, irrespective of mood state.

Sex differences in Wisconsin Schizotypy Scales--a meta-analysis

Previous single studies have found inconsistent results on sex differences in positive schizotypy, women scoring mainly higher than men, whereas in negative schizotypy studies have often found that men score higher than women. However, information on the overall effect is unknown. In this study, meta-analytic methods were used to estimate sex differences in Wisconsin Schizotypy Scales developed to measure schizotypal traits and psychosis proneness. We also studied the effect of the sample characteristics on possible differences. Studies on healthy populations were extensively collected; the required minimum sample size was 50. According to the results, men scored higher on the scales of negative schizotypy, ie, in the Physical Anhedonia Scale (n = 23 studies, effect size, Cohen d = 0.59, z test P < .001) and Social Anhedonia Scale (n = 14, d = 0.44, P < .001). Differences were virtually nonexistent in the measurements of the positive schizotypy, ie, the Magical Ideation Scale (n = 29, d = -0.01, P = .74) and Perceptual Aberration Scale (n = 22, d = -0.08, P = .05). The sex difference was larger in studies with nonstudent and older samples on the Perceptual Aberration Scale (d = -0.19 vs d = -0.03, P < .05). This study was the first one to pool studies on sex differences in these scales. The gender differences in social anhedonia both in nonclinical samples and in schizophrenia may relate to a broader aspect of social and interpersonal deficits. The results should be taken into account in studies using these instruments.

The psychoses: cluster 3 of the proposed meta-structure for DSM-V and ICD-11

BACKGROUND

In an effort to group mental disorders on the basis of etiology, five clusters have been proposed. Here we consider the validity of the cluster comprising selected psychotic and related disorders.

METHOD

A group of diagnostic entities classified under schizophrenia and other psychotic disorders in DSM-IV-TR were assigned to this cluster and the bordering disorders, bipolar (BD) and schizotypal personality disorders (SPD), were included. We then reviewed the literature in relation to 11 validating criteria proposed by the DSM-V Task Force Study Group.

RESULTS

Relevant comparisons on the 11 spectrum criteria are rare for the included disorders except for schizophrenia and the two border conditions, BD and SPD. The core psychosis group is congruent at the level of shared psychotic psychopathology and response to antipsychotic medication. BD and SPD are exceptions in that psychosis is not typical in BD-II disorder and frank psychosis is excluded in SPD. There is modest similarity between schizophrenia and BD relating to risk factors, neural substrates, cognition and endophenotypes, but key differences are noted. There is greater support for a spectrum relationship of SPD and schizophrenia. Antecedent temperament, an important validator for other groupings, has received little empirical study in the various psychotic disorders.

CONCLUSIONS

The DSM-IV-TR grouping of psychotic disorders is supported by tradition and shared psychopathology, but few data exist across these diagnoses relating to the 11 spectrum criteria. The case for including BD is modest, and the relationship of BD to other mood disorders is addressed elsewhere. Evidence is stronger for inclusion of SPD, but the relationship with other personality disorders along the 11 criteria is not addressed and the absence of psychosis presents a conceptual problem. There are no data along the 11 spectrum criteria that are decisive for a cluster based on etiology, and inclusion of BD and SPD is questionable.

Effect of aripiprazole on self-reported anhedonia in bipolar depressed patients

Some studies have suggested that aripiprazole might be a useful treatment for bipolar depression. There are no studies evaluating the effect of aripiprazole on anhedonia. In the present study, effects of aripiprazole were investigated under routine clinical conditions. Anhedonia was measured in patients with bipolar disorder type I (n=50) using the self-rated Snaith-Hamilton Pleasure Scale (SHAPS) and depression was assessed using the Montgomery-Asberg Depression Rating Scale. Anhedonia was present in 52% of all patients and was significantly reduced during treatment with aripiprazole. All patients completed the 16-week trial. Only 16% of patients experienced side effects (akathisia, headache). Future studies should investigate the specificity of anti-anhedonic and anti-depressant properties of aripiprazole in bipolar patients.

Anhedonia as a phenotype for the Val158Met COMT polymorphism in relatives of patients with schizophrenia

The Val(158)Met polymorphism of the catechol-O-methyltransferase (COMT) gene has been associated with aspects of schizophrenia that are possibly related to the disorder's pathogenesis. The present study investigated the Val(158)Met polymorphism in relation to anhedonia--a construct central to negative schizotypy. Anhedonia and other schizotypal characteristics were assessed in relatives of patients with schizophrenia, relatives of patients with bipolar disorder, and nonpsychiatric controls using the Chapman schizotypy scales and the Schizotypal Personality Questionnaire. Compared with controls, relatives of individuals with schizophrenia had elevated scores on Chapman scales for social anhedonia and physical anhedonia, while relatives of patients with bipolar disorder exhibited only increased scores on the Social Anhedonia Scale. As a group, relatives of patients with schizophrenia who were homozygous for the val allele of the COMT polymorphism showed the highest elevations in self-reported social and physical anhedonia. Associations with the COMT polymorphism were absent in relatives of patients with bipolar disorder and control participants. Findings suggest that anhedonia is manifest in individuals who carry genetic liability for schizophrenia and is associated with the Val(158)Met polymorphism of the COMT gene.