A transdiagnostic network analysis of motivation and pleasure, expressivity and social functioning


In this blog post, I will summarize a recent article published in Nature Mental Health by Hu et al. (2023) , which examined the inter-relationship pattern between negative symptoms and social functioning in patients with schizophrenia, bipolar disorder and major depressive disorder.

Negative symptoms are the loss of normal functions, such as motivation, pleasure, expressivity and sociality, that are often found in psychiatric disorders. They are especially important for schizophrenia, as they are key determinants of poor social functioning and long-term prognosis. However, negative symptoms are not specific to schizophrenia, and can also be observed in bipolar disorder and major depressive disorder.

Schizophrenia, a complex and severe mental disorder, affects millions of people worldwide. One of the core symptoms that often manifests in individuals with schizophrenia is a significant impairment in motivation and pleasure, known as the Motivation and Pleasure (MAP) deficit. MAP deficits can have profound impacts on an individual’s quality of life, ability to function, and overall well-being. This article delves into the intricacies of MAP deficits in schizophrenia, exploring their underlying mechanisms, contributing factors, and potential treatment approaches.

Understanding Motivation and Pleasure in the Context of Schizophrenia

Motivation and pleasure are fundamental aspects of human behavior, driving individuals to pursue goals, engage in activities, and experience joy. In the context of schizophrenia, MAP deficits lead to a loss of interest in previously enjoyed activities, reduced enthusiasm for social interactions, and difficulties initiating and sustaining goal-directed behaviors. This constellation of symptoms, collectively known as anhedonia and apathy, significantly hinders an individual’s ability to find pleasure in life and dampens their willingness to participate in activities they once found enjoyable.

Anhedonia and Apathy: Different Facets of MAP Deficits

Anhedonia refers to the inability to experience pleasure from activities or stimuli that would typically be rewarding or enjoyable. It is a hallmark symptom of schizophrenia and can be classified into two subtypes: anticipatory anhedonia, which involves a reduced ability to feel excitement or pleasure in anticipation of future events, and consummatory anhedonia, which relates to the diminished pleasure experienced during ongoing activities or interactions.

Apathy, on the other hand, is characterized by a lack of interest, motivation, or emotional responsiveness. People with schizophrenia may display a diminished desire to engage in social interactions, hobbies, work, or other aspects of life, leading to social withdrawal and isolation.

Biological Underpinnings of MAP Deficits

The exact neurobiological mechanisms that underlie MAP deficits in schizophrenia remain the subject of ongoing research. However, there are several key areas of the brain and neurotransmitter systems that are thought to be involved.

  • Dopaminergic Dysfunction: Dopamine, a neurotransmitter associated with pleasure and reward processing, plays a crucial role in MAP deficits. Abnormalities in the mesolimbic and mesocortical dopamine pathways have been implicated in the reduced experience of pleasure and motivation observed in schizophrenia.
  • Prefrontal Cortex Dysfunction: The prefrontal cortex, responsible for executive functions such as decision-making and goal-directed behavior, is also implicated in the development of anhedonia and apathy. Disruptions in this brain region can contribute to deficits in planning, initiating tasks, and maintaining motivation.
  • Ventral Striatum and Nucleus Accumbens: These brain regions are integral components of the brain’s reward system and are involved in processing pleasure and motivation. Dysregulation in these areas can lead to diminished experiences of pleasure and reduced motivation to engage in rewarding activities.

Psychosocial Factors Contributing to MAP Deficits

Beyond biological factors, various psychosocial elements can also contribute to MAP deficits in schizophrenia.

  • Social Isolation: Reduced social interaction and feelings of loneliness can exacerbate anhedonia and apathy, creating a negative feedback loop where social withdrawal further reinforces these symptoms.
  • Stigma and Discrimination: The stigma associated with mental illness, including schizophrenia, can lead to feelings of shame and self-stigmatization, further diminishing motivation and pleasure.
  • Impaired Social Cognition: Difficulties in understanding social cues and intentions may lead to social withdrawal and reduced motivation to interact with others.

The new research…..

The authors of the article used a transdiagnostic approach, which means that they studied the symptoms across different disorders, rather than focusing on a single diagnosis. This way, they aimed to identify the common and distinct patterns of negative symptoms and social functioning in different psychiatric conditions.

The authors recruited 192 patients with schizophrenia, 67 patients with bipolar disorder and 92 patients with major depressive disorder, and assessed their negative symptoms using the Clinical Assessment Interview for Negative Symptoms (CAINS).

The CAINS measures two factors of negative symptoms: motivation and pleasure (MAP) and expressivity (EXP). The authors also measured the patients’ social functioning using the Personal and Social Performance Scale (PSP).

The authors then used network analysis, a statistical technique that allows to visualize and quantify the connections between different variables, to examine how the MAP and EXP factors, as well as other clinical characteristics (such as depression, anxiety, mania and psychosis), were related to each other and to social functioning in each disorder group.

The results showed that the MAP factor was the central node in the transdiagnostic network at both symptom-domain and symptom-item levels.

This means that the MAP factor had the strongest connections with other variables, and was the most influential factor in determining social functioning across different disorders. The EXP factor was also connected to social functioning, but to a lesser extent than the MAP factor.

The authors also found some disorder-specific patterns in the network.

For example, depression was more strongly connected to negative symptoms and social functioning in bipolar disorder and major depressive disorder than in schizophrenia.

Anxiety was more strongly connected to negative symptoms in bipolar disorder than in schizophrenia or major depressive disorder.

Mania was only connected to negative symptoms in bipolar disorder, while psychosis was only connected to negative symptoms in schizophrenia.

The authors concluded that their findings support that the MAP factor is the core symptom in determining social functioning across different psychiatric disorders. They suggested that interventions targeting the MAP factor may have transdiagnostic benefits for improving social functioning in patients with psychiatric conditions.

This article provides a novel insight into the role of negative symptoms on social functioning from a transdiagnostic perspective. It also demonstrates the usefulness of network analysis for studying the complex interplay between different psychopathological symptoms and domains. The article has some limitations, such as the cross-sectional design, the use of self-report measures, and the lack of healthy controls. Future studies may address these limitations by using longitudinal designs, objective measures, and including healthy participants for comparison.

reference link: https://www.nature.com/articles/s44220-023-00102-3


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