Schizophrenia vs Schizoaffective disorder

Schizophrenia is a complex chronic mental disorder that affects a person’s thoughts, emotions, and behavior. It typically is characterized by symptoms such as hallucinations, delusions, disorganized thinking, and social withdrawal. Schizoaffective disorder was introduced in 1933 as it combines features of schizophrenia and mood disorders, such as depression or bipolar disorder. It is characterized by having depressive, manic, or hypomanic episodes with delusions and hallucinations that occur simultaneously or within a few days of each other. 

In a cross-sectional study, researchers sought out to compare the patterns of basic and social cognitive function between schizophrenia and schizoaffective through various tasks. Basic cognitive measures included verbal and nonverbal memory tasks (ex. Logical Memory I and II, Figural Memory subtest from Wechsler Memory Scale), digit span test, verbal learning test, Wisconsin Card Sorting Test, and Digit Symbol Substitution subtest. For measuring social cognition, the Hinting Task and the Bell Lysaker Emotion Recognition Task were used.   

From 1988-2003, participants were recruited from a VA outpatient clinic and a Connecticut Mental Health Center outpatient clinic. The study excluded participants that had a history of traumatic brain injury or other known neurological diseases were excluded. A total of 272 participants with a confirmed DSM-5 diagnoses of schizophrenia or schizoaffective disorder met the inclusion criteria. Prior to the study starting, the participants completed a neuropsychological test to establish a baseline. Multivariant analysis of variance was used for the basic cognitive and social cognitive variables. 

Overall, results showed that there was no statistically significant difference between the two conditions on basic cognitive measures however, individuals with schizoaffective disorder performed significantly better on one of the Hinting Task, which measures the ability to infer the real intentions behind indirect speech. When univariate analysis was used, individuals with schizoaffective disorder showed less impairment in figure recall task. It is interesting to note that though may not be statistically significant, in all the areas where the two conditions differed, individuals with schizoaffective disorder had less impaired performance. When looking at demographic differences, individuals with schizoaffective disorder were significantly more likely to be female, married, and Caucasian. 

The researchers concluded that since the results of the Hinting Task was the only task that was statistically significant, they speculate that schizoaffective patients have more intact Theory of Mind performance, meaning they are better able understand themselves and others as mental beings, based on beliefs, desires, emotions, and intentions, but have similar emotional perception as schizophrenic patients. 

In a more recent 2019 study, researchers at York University sought out to determine to what degree do schizophrenia and schizoaffective disorder differ on cognitive performance tests and if cortical thickness in areas of the social brain network on brain show sensitivity towards distinguishing between the two disorders. A total of 73 participants, recruited from various outpatient clinics, diagnosed with either schizophrenia or schizoaffective disorder without developmental or learning disability, other neurological or endocrine disorders, or concurrent diagnoses of substance use disorder were included. 11 cognitive/social tasks were given to assess for cognitive performance. Results showed that schizophrenia and schizoaffective disorder are in fact, largely indistinguishable when assessing cognitive performance, including analysis of brain network structures. The only difference was noted among individuals with schizoaffective disorder as they were found to have more proficient emotional regulation compared to the individuals with schizophrenia and close scores to the control values. The researchers concluded that the mood disorder portion of schizoaffective disorder, may enhance emotional processing making the affect more noticeable and able to detect. Additionally, depressive symptoms were found to be more common in schizoaffective individuals, suggesting that mood disturbance should be specifically assessed upon clinical evaluation. Among the brain MRIs analyzed, similar results of reduced thickness in the temporal and medial regions associated with social processing seen in schizophrenia was also seen in schizoaffective individuals. 

Sources:

• Fiszdon, Joanna M et al. “A comparison of basic and social cognition between schizophrenia and schizoaffective disorder.” Schizophrenia research vol. 91,1-3 (2007): 117-21. doi:10.1016/j.schres.2006.12.012 https://pubmed.ncbi.nlm.nih.gov/17258431/
• Hartman, Leah I et al. “The continuing story of schizophrenia and schizoaffective disorder: One condition or two?.” Schizophrenia research. Cognitionvol. 16 36-42. 10 Feb. 2019, doi:10.1016/j.scog.2019.01.001 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6370594/