Amy Lieberman, Winner of the 2019 Three-Minute Talks Competition
Amy Lieberman: My name is Amy Lieberman. Most people with schizophrenia demonstrate cognitive impairment. However, the extent of and the path toward that impairment varies substantially when described by patients and their families.
The classic description of schizophrenia involves developing normally through adolescence. But with the onset of psychotic symptoms, cognition actually declines, like in gold. However, some describe cognitive impairment that was present throughout their childhood, often worsening with the onset of illness, like in red.
And yet, some describe a relatively stable trajectory of cognitive development. Despite the emergence of psychotic symptoms, their cognitive abilities are only mildly affected. But we see our patients with schizophrenia once they are already sick. Meaning for the most part, we're only able to obtain cognitive data from adults.
So in light of this, we've developed a way to use quantitative adult, cognitive test data to capture those qualitative narratives of cognitive development. And to do this we focused on two cognitive assessments.
The first is the Weschler Adult Intelligence Scale, or the WAIS, which measures a range of abilities and yields an estimate of current intelligence, or what we all think of when we hear the word IQ. The second is the Wide Range Achievement Test, or the WRAT, which measures reading abilities. And for most people, reading scores actually approximate their IQ scores. However, unlike the WAIS, the abilities measured by the WRAT mature early in adolescence and they become ingrained, which means these skills remain stable even in the face of brain injury or illness.
So because of that, we can use the WRAT to estimate what we call premorbid IQ in schizophrenia. Or in other words, it gauges how our participants were performing cognitively before they became acutely psychotic. We then use cluster analysis to understand patterns in the data from these two tests. And, in fact, three distinct groups of performance patterns aligned with the three common narratives that we're often told about.
For example, one group of participants exhibited a high WRAT, high WAIS pattern with relatively unimpaired performance on either test. Due to the high WRAT score, there is limited evidence of premorbid impairment. And because of the high WAIS score, there's limited evidence of current impairment suggesting an overall stable trajectory of cognitive development.
Another group of participants exhibited a low WRAT, low WAIS pattern with impaired performance on both tests. So this pattern suggests enduring problems with cognition that began in childhood before the onset of illness. And the third group exhibited particularly interesting high WRAT, low WAIS performance pattern with far better reading scores than current intelligence. So these individuals seem to have been doing okay before they became sick. But we see a marked change when it comes to their current abilities.
So by utilizing those two standardized tests, we believe we're capturing the patterns of cognitive development that are often described. In fact, differences in several other variables across the groups like diagnosed ADHD and educational attainment align with and support our clustering method as well. And importantly, finding objective ways to cluster patients with schizophrenia allows us to simplify, somewhat, this complex and heterogeneous population, allowing traction for future investigation into biological differences across the groups and more precise treatment approaches.