In a review article, (Mäkinen et al., 2008) reported that over half of individuals experiencing their first-episode of psychosis exhibit negative symptoms, with a third demonstrating persistent negative symptoms. These symptoms are associated with diminished subjective quality of life and hindered rehabilitation (Packer et al., 1997). Individuals with schizophrenia often face challenges in relationships with relatives and in maintaining daily functions, primarily because of feelings of apathy and a lack of motivation. (Correll & Schooler, 2020) indicated that negative symptoms can be prevented from progressing to a residual stage, underscoring the importance of understanding such symptoms’ psychopathology and treatment.
Studies related to the psychopathology and treatment of negative symptoms have often emphasized the structure of these symptoms. The consensus conceptualization of negative symptoms involves two factors: expressive (alogia and blunted affect) and experiential (avolition, anhedonia, and asociality) negative symptoms (Glenthøj et al., 2020; Schlosser et al., 2015). The prior study reported that experiential negative symptoms more profoundly influence social functioning than expressive negative symptoms do (Marder & Galderisi, 2017).
Researchers have used the positive and negative syndrome scale and social functioning to assess patients on the schizophrenia spectrum and have discovered experiential negative symptoms to significantly affect social functioning, everyday activities, and vocational functioning. By contrast, research has indicated expressive negative symptoms to have a negligible effect on social and vocational functioning (Harvey et al., 2017; Paul et al., 2023). Another study confirmed the substantial influence of experiential negative symptoms on quality of life in a study involving 275 participants with schizophrenia (Savill et al., 2016). Further validated the stronger effect of experiential over that of expressive negative symptoms on social functioning (Glenthøj et al., 2020).
These findings raise the critical question of how experiential negative symptoms influence social functioning. The core symptoms of experiential deficits include asociality, anhedonia, and avolition, which are collectively categorized as avolition–apathy negative symptoms (AA; (Marder & Galderisi, 2017; Mäkinen et al., 2008). Research has indicated that a relationship exists between experiential negative symptoms and neurocognitive deficits (Chey et al., 2002; Hovington & Lepage, 2012; Sampedro et al., 2021). Neuroimaging research reveals associations between these symptoms and a propensity for selecting low-effort options, along with excessive effort-discounting, implicating brain regions such as the insula, hippocampus, amygdala, reward system, and frontal cortex (Galderisi et al., 2018).
Patients with schizophrenia often exhibit withdrawal from interpersonal activities and diminished motivation for engaging in enjoyable activities. A case–control study by (Strauss et al., 2016) revealed that individuals with schizophrenia who experienced heightened levels of avolition and anhedonia exhibited less of an inclination towards seeking out rewarding experiences than did healthy controls. Furthermore, a study involving 58 patients with schizophrenia examined the relationships between neurocognitive function, AA, expressive deficit negative symptoms (DE), and real-life functioning. The study’s results indicated that when AA and DE were considered, the effect of neurocognition on real-life functioning diminished (Yang et al., 2021). Thus, neurocognitive function may be a distal factor in social functioning, whereas experiential negative symptoms could be a proximal factor.
Evidence regarding the effect of experiential negative symptoms on social functioning, however, is not always consistent. A 3-year follow-up study indicated that the influence of these symptoms might fluctuate over time (Austin et al., 2019). In addition, (Kasanova et al., 2018) discovered that some patients with schizophrenia, despite having reduced engagement in social activities, experienced a certain amount of hedonism. (Harvey et al., 2017) identified other factors that could influence the relationship between experiential negative symptoms and social functioning. A review by (Marder & Galderisi, 2017) highlighted the role of dysfunctional beliefs, such as negative expectations about oneself, the future, or the environment, in diminishing the motivation of individuals with schizophrenia to engage in social activities.
One study conducted a 1-year follow-up study investigating the effect of negative expectations on social withdrawal. The study revealed that negative expectations were predictive of poor social functioning, even after neurocognition was controlled for. This finding emphasizes the importance of considering the role of negative thoughts in social functioning (Grant & Beck, 2010). The cognitive–behavioral therapy (CBT) model of negative symptoms for schizophrenia indicates that defeatist performance beliefs may link neurocognition (i.e., memory, attention, and executive function), negative symptoms, and impaired functioning (Grant & Beck, 2009). Beck et al. (2018) reported that when individuals with schizophrenia fail to meet their own performance expectations, they are likely to doubt their abilities, which leads to frustration, reduced motivation, and exacerbated negative symptoms. (Ventura et al., 2014) observed that such patterns can impede daily functioning. However, studies have not consistently demonstrated a clear relationship between neurocognition, self-defeatist beliefs, negative symptoms, and social functioning.
For example, a cross-sectional study by (Luther et al., 2018) provided evidence supporting the existence of an effect of self-defeatist beliefs on negative symptoms, whereas (Quinlan et al., 2014) indicated that defeatist beliefs mediated the relationship between neurocognition and negative symptoms. However, these two studies have reported no relationship between defeatist beliefs and daily functioning. Other studies, such as (Couture et al., 2011; Mervis et al., 2017), have reported self-defeatist thoughts to have a direct effect on social functioning. They observed that patients with schizophrenia had higher work motivation and retention rates after participating in CBT-based vocational intervention programs focused on reducing self-defeatist beliefs. Additionally, a neuroimaging study by (Milev et al., 2005) revealed that dysfunctional beliefs may mediate the relationship between negative symptoms and social functioning.
Although studies on the topic have reported inconsistent results, the present study proposes that self-defeatist beliefs mediate the relationship between negative symptoms and social functioning. This hypothesis aligns with the CBT model of negative symptoms, in which maladaptation is considered to be a reaction to the consequences of negative symptoms, which are perpetuated by dysfunction beliefs (Beck et al., 2018; Campellone et al., 2016; Perivoliotis & Cather, 2009). This understanding of negative symptoms is supported by a randomized study by (Granholm et al., 2014), which found that changes in dysfunction correlated with improvements in social functioning.
Few studies have investigated the relationships between neurocognition, self-defeatist beliefs, experiential negative symptoms, and social functioning. (Saleh et al., 2021) argued that self-defeatist beliefs mediated the relationship between motivational and reward processing deficits and negative symptoms, particularly apathy and avolition, rather than that between alogia and blunted affect. A randomized clinical trial identified self-defeatist beliefs to play a mediating role in the relationship between experiential negative symptoms and social functioning (Granholm et al., 2018).
The present study proposed and analyzed a hypothesized model of negative symptoms (Fig. 1) by using structural equation modeling (SEM). It examined the following hypothesized paths: (1) neurocognition may directly affect experiential negative symptoms; (2) neurocognition may directly influence self-defeatist beliefs; (3) experiential negative symptoms may directly influence self-defeatist beliefs; (4) self-defeatist beliefs may directly affect daily functioning; (5) neurocognition may influence social functioning; (6) experiential negative symptoms may directly affect social functioning; and (7) self-defeatist beliefs may mediate the relationship between experiential negative symptoms and social functioning.