Developmental instability in social anhedonia: an examination of minor physical anomalies and clinical characteristics

Ectodermal disturbance in development shared by anorexia and schizophrenia may reflect neurodevelopmental abnormalities

Minor physical abnormalities (MPA) are subtle dysmorphic features of bodily structures that have little or no impact on function. Most MPA develop during the first gestational trimester and are considered as important indicators of neuroectodermal deficiencies emerging during early brain development. A higher frequency of MPA was confirmed in schizophrenia patients and their relatives, when compared to controls. These findings are consistent with the neurodevelopmental model of schizophrenia. A neurodevelopmental component amongst other risk factors has also been recently proposed for anorexia nervosa (AN). The current study aimed to assess MPA frequency in adolescent inpatients with either schizophrenia spectrum disorders (SSD) or AN as compared to healthy controls (HC). The Waldrop Scale was used for assessing MPA. The mean MPA total score and mean head subscore was significantly higher in both test groups than in HC. There were no statistically significant differences between SSD and AN groups. The MPA profile (not frequency) was similar in all three groups. This finding is consistent both with widely acknowledged neurodevelopmental schizophrenia hypothesis as well as with more recent neurodevelopmental model of AN. Nevertheless, the findings should not be overgeneralized and further studies are warranted.

Fluctuating asymmetry in patients with schizophrenia is related to hallucinations and thought disorganisation

Fluctuating asymmetry represents the degree to which the right and left side of the body are asymmetrical, and is a sign of developmental instability. Higher levels of fluctuating asymmetry have been observed in individuals within the schizophrenia spectrum. We aimed to explore the associations of fluctuating asymmetry with psychotic and affective symptoms in schizophrenia patients, as well as with propensity to these symptoms in non-clinical individuals. A measure of morphological fluctuating asymmetry was calculated for 39 patients with schizophrenia and 60 healthy individuals, and a range of clinical and subclinical psychiatric symptoms was assessed. Regression analyses of the fluctuating asymmetry measure were conducted within each group. In the patient cohort, fluctuating asymmetry was significantly associated with the hallucination and thought disorganisation scores. T-test comparisons revealed that the patients presenting either hallucinations or thought disorganisation were significantly more asymmetrical than were the healthy individuals, while the patients without these key symptoms were equivalent to the healthy individuals. A positive association with the anxiety score emerged in a subsample of 36 healthy participants who were rated on affective symptoms. These findings suggest that fluctuating asymmetry may be an indicator of clinical hallucinations and thought disorganisation rather than an indicator of schizophrenia disease.

Asymmetry and empathy: Higher asymmetry is associated with lower levels of mentalizing

People differ in their mentalizing abilities. Though past research suggests that individual differences in exposure to prenatal testosterone may be able to explain why some people excel at mentalizing, while others struggle, meta-analyses yield a null relationship between 2D:4D ratio (a proxy for prenatal testosterone) and mentalizing. Importantly, however, past research has not examined the asymmetrical differences between the digit ratios on the right and left hands. In the current work, we test whether the difference between the digit ratios of the left and right hands may function as a better predictor of mentalizing than digit ratio alone. In Study 1, we begin by validating an online, self-report measure of 2D:4D ratio, providing test-retest reliability, convergent, and concurrent validity for our measure. In Study 2, we demonstrate that a) 2D:4D is quadratically related to asymmetry, b) asymmetry is negatively associated with mentalizing, and c) the relationship between asymmetry and mentalizing cannot be explained by the relationship between asymmetry and short-term memory. Taken together, our results paint a more nuanced picture of the relationship between digit ratio and mentalizing ability.

Schizotypy as an organizing framework for social and affective sciences

Schizotypy, defined in terms of commonly occurring personality traits related to the schizophrenia spectrum, has been an important construct for understanding the neurodevelopment and stress-diathesis of schizophrenia. However, as schizotypy nears its sixth decade of application, it is important to acknowledge its impressively rich literature accumulating outside of schizophrenia research. In this article, we make the case that schizotypy has considerable potential as a conceptual framework for understanding individual differences in affective and social functions beyond those directly involved in schizophrenia spectrum pathology. This case is predicated on (a) a burgeoning literature noting anomalies in a wide range of social functioning, affiliative, positive and negative emotional, expressive, and social cognitive systems, (b) practical and methodological features associated with schizotypy research that help facilitate empirical investigation, and (c) close ties to theoretical constructs of central importance to affective and social science (eg, stress diathesis, neural compensation). We highlight recent schizotypy research, ie providing insight into the nature of affective and social systems more generally. This includes current efforts to clarify the neurodevelopmental, neurobiological, and psychological underpinnings of affiliative drives, hedonic capacity, social cognition, and stress responsivity systems. Additionally, we discuss neural compensatory and resilience factors that may mitigate the expression of stress-diathesis and functional outcome, and highlight schizotypy's potential role for understanding cultural determinants of social and affective functions.

The Concept of Schizophrenia: From Unity to Diversity

After over 100 years of research without clarifying the aetiology of schizophrenia, a look at the current state of knowledge in epidemiology, genetics, precursors, psychopathology, and outcome seems worthwhile. The disease concept, created by Kraepelin and modified by Bleuler, has a varied history. Today, schizophrenia is considered a polygenic disorder with onset in early adulthood, characterized by irregular psychotic episodes and functional impairment, but incident cases occur at all ages with marked differences in symptoms and social outcome. Men’s and women’s lifetime risk is nearly the same. At young age, women fall ill a few years later and less severely than men, men more rarely and less severely later in life. The underlying protective effect of oestrogen is antagonized by genetic load. The illness course is heterogeneous and depressive mood the most frequent symptom. Depression and schizophrenia are functionally associated, and affective and nonaffective psychoses do not split neatly. Most social consequences occur at the prodromal stage. Neither schizophrenia as such nor its main symptom dimensions regularly show pronounced deterioration over time. Schizophrenia is neither a residual state of a neurodevelopmental disorder nor a progressing neurodegenerative process. It reflects multifactorial CNS instability, which leads to cognitive deficits and symptom exacerbations.

Psychotic-like symptoms and positive schizotypy are associated with mixed and ambiguous handedness in an adolescent community sample

The objective of this study was to replicate the association between atypical handedness and psychosis-proneness in a representative sample of adolescents from the general population. It expands previous studies by (1) analyzing a variety of atypical handedness indexes (left, mixed, ambiguous, and inconsistent), (2) measuring comprehensively the multidimensionality of psychosis-proneness, and (3) analyzing the association of different patterns of atypical handedness with nonclinical dimensions of both trait (schizotypy) and sub-clinical symptom (psychotic-like experiences) levels. Seven hundred and twenty-eight adolescents were assessed for handedness by the 12-item self-report Annett Hand Preference Questionnaire and for psychosis-proneness by the Oxford-Liverpool Inventory of Feelings and Experiences and the Community Assessment of Psychic Experiences scales. Writing-hand alone did not detect associations between laterality and psychosis-proneness. Mixed- rather than left-handedness was related to psychosis-proneness, and this was more evident when analyzing subjects with ambiguous handedness exclusively. When analysis was restricted to subjects with non-ambiguous handedness, strong left-handedness was related to psychosis-proneness. The positive dimension showed a stronger association than the negative one with atypical handedness. Results partially support mixed-handedness as a marker of developmental disorders underlying both atypical lateralization and psychosis-proneness. Among various possible mixed-handedness patterns, inconsistent hand use across primary actions, and for the same action across time, seems particularly related to psychosis-proneness and thus requires further exploration.