COGNITIVE impairments remain a defining feature of schizophrenia, with new research highlighting processing speed as a particularly affected domain. An updated systematic review and meta-analysis found symbol coding tasks consistently among the most impaired tests for people with schizophrenia.
Revisiting Cognitive Impairment in Schizophrenia
Schizophrenia is a complex psychiatric disorder that affects thinking, perception, and daily functioning. Cognitive deficits are widely recognised as a major contributor to reduced quality of life in affected individuals, yet the specific domains most impacted remain under study. Understanding which aspects of cognition are consistently impaired in schizophrenia is essential for developing targeted interventions and improving functional outcomes. This study used the keyword “schizophrenia” to focus on the persistence of central processing speed deficits across diverse patient populations.
Systematic Review and Meta-Analysis Findings
The researchers identified 115 studies from PubMed and PsycINFO, encompassing 10 114 people with schizophrenia and 13 235 controls. Symbol coding tests of processing speed were evaluated alongside 49 other cognitive measures. Results showed that symbol coding was among the most impaired tasks (Hedges g = −1.52; 95% CI, −1.65 to −1.40) and was significantly more impaired than 34 of the other cognitive tests. Moderator analyses revealed that factors such as intelligence quotient, age differences from controls, sex composition, inpatient status, and inclusion of schizoaffective or schizophreniform diagnoses influenced the severity of impairment. These findings indicate that processing speed deficits are robust and may reflect underlying disruptions in brain connectivity, contributing to broader cognitive deficits in schizophrenia.
Implications For Clinical Practice and Research
The consistent impairment of processing speed highlights a potential target for cognitive remediation and therapeutic interventions. Clinicians and researchers should consider focusing on tasks that measure symbol coding and related processing speed domains to monitor treatment outcomes. Understanding the neurobiological mechanisms underlying these deficits could inform personalised approaches, improve cognitive rehabilitation, and ultimately enhance quality of life for people with schizophrenia.
Reference
Pratt DN et al. Processing speed impairment in schizophrenia: an updated systematic review and meta-analysis. JAMA Psychiatry. 2025;DOI:10.1001/jamapsychiatry.2025.3893.
