Reading skills in mental illness: A multimodal analysis

Abstract

Reading is a complex process involving multiple skills – i.e., phonological processing, comprehension, and word recognition. It is also a significant predictor of socio-economic status, academic achievement, and has vast importance in everyday functioning. Reading deficits can lead to maladaptive behaviour and consequently increase the risk of incarceration. Severe reading skills deficits are present in schizophrenia, and to some extent in people with psychopathy and forensic populations (Chapter 2 – systematic review and meta-analysis). Considering the overlap between discreet clinical diagnoses and the presence of symptoms and psychopathology-related traits in non-clinical populations, this thesis aimed to examine the behavioural and neurofunctional associations between reading skills and dimensional psychopathology-related traits in the general and clinical populations. To address these aims, three empirical investigations were carried out: i) behavioural studies (Chapters 4 and 5) investigating the relationship between reading-related skills, as indexed by performance on a lexical decision task (LDT) requiring word-nonword recognition, and a range of psychopathologyrelated traits (schizotypy, psychopathy, impulsivity, and affective traits) in a general population sample (N = 78), ii) a functional magnetic resonance imaging (fMRI) study (Chapter 6) investigating the neural correlates of this relationship (N = 22), and iii) a preliminary clinical study (Chapter 7) investigating the relationship between reading skills of phonological processing and comprehension, dimensional psychopathology, and cognition (verbal learning and memory, IQ, and executive functioning) in a forensic psychiatric sample (N = 15). The findings suggest that traits of positive schizotypy (Unusual Experiences), fearless dominance (Meanness) and callous aggression (Boldness) in psychopathy, and motor impulsivity can modulate behavioural responses in word-nonword recognition (LDT performance) in the general population. Higher motor impulsivity was the trait most strongly associated with lower LDT performance accuracy in non-native speakers. At the neural level also, motor impulsivity was most consistently associated with lower activity in some of the brain areas that are crucial for word recognition, namely the fusiform and inferior frontal gyri (IFG). In the forensic psychiatric sample, 13/15 patients were diagnosed with a psychotic disorder and all reading skills were significantly below their age norms and showed some association with executive function and verbal learning. In this sample, Lifestyle psychopathy was significantly associated with poor LDT performance, especially in low-frequency words recognition and Cognitive Perceptual aspect of positive schizotypy with severe deficits in reading comprehension, overall reading ability, and poor low-frequency word recognition. In conclusion, positive schizotypy and psychosis seem to be associated with poor reading skills. Higher psychopathy and motor impulsivity traits seem to predict of poor reading skills across the general and clinical populations and modulate neural activity during correct word-nonword recognition. These findings provide insight into the relationship between dimensional psychopathology-related traits, their comorbidities, and reading skills in clinical and non-clinical populations, and suggest that poor reading skills in clinical populations should be considered as important treatment targets.