Schizophrenia linked to worse verbal memory than 22q11.2 deletion syndrome
MedWire News: Young patients with schizophrenia show marked deficits in verbal memory compared with intellectually matched youths with 22q11.2 deletion syndrome (22qDS), research shows.
Since patients with 22qDS have inherently low catechol-O-methyltransferase (COMT) activity, the findings provide support for the role of COMT in cognition, and raise the possibility of pharmacological interventions for cognition via COMT inhibition.
The 22q11.2 deletion syndrome is caused by a micro-deletion in chromosome 22 and is characterized by high prevalence (69–90%) of intellectual disabilities, explain study author Eugenia Kravariti (King’s College London, UK) and colleagues.
Approximately one third of 22qDS patients develop schizophrenia in young adulthood, and 22qDS–schizophrenia is considered a genetic subtype of schizophrenia.
The two conditions are thought to have genetic and neuropsychological similarities, but early studies show distinct differences in memory profile.
“Confirming differences in memory function between the two disorders, and identifying their genetic determinants, can help to define genetic subtypes in both syndromes, and identify genetic risk factors for the emergence of psychosis,” the researchers comment in the journal Research in Developmental Disabilities.
Kravariti et al therefore conducted a study of verbal and visual memory in 29 children and adolescents with 22qDS and 15 intellectually matched youths with schizophrenia using age-appropriate, directly comparable, Wechsler scales.
They found that verbal memory was markedly superior in participants with 22qDS than in those with schizophrenia, with a difference of 21 points on the Wechsler scale. Notably the 22qDS patients performed at a level that just fell short of the average range of ability for the general population.
By contrast, there were no differences in visual memory between the two groups.
Kravariti et al comment: “Our findings raise the possibility that fundamental genetic differences between 22qDS and schizophrenia give the former a strong advantage in verbal memory, which exceeds what would be considered ‘typical’ or ‘preserved’ in a population with learning disabilities.
They add: “Identifying the genetic determinants of this dissociation can help to define genetic subtypes in both syndromes, identify genetic risk factors for the emergence of psychosis, and develop pharmacological interventions for cognitive dysfunction.”
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By Andrew Czyzewski