Neurocognitive dysfunction is shown to be a core feature of schizophrenia, and neurocognitive impairments have been well documented in early-onset schizophrenia (EOS) as well as in adult-onset schizophrenia (AOS) samples. EOS is usually considered a more severe form of schizophrenia compared to AOS, with more premorbid impairments and a poorer clinical course and outcome. The general agreement is that EOS patients have more prominent neurocognitive deficits than AOS patients, even though only one study has compared cognitive function in EOS and AOS groups directly.
Executive functions (EF) are of specific interest. Because of their central role in cognitive processes, EF probably contribute to other observed cognitive dysfunctions and they add prominently to poor psychosocial functioning. However, the lack of a standardized, consensus assessment battery has made the comparison of neuropsychological test results difficult, and there is inconsistency regarding an average profile of the EOS group. In addition, an unanswered question is whether the cognitive deficits in this group are specific or generalized, hence whether some aspects of neurocognitive function are more affected than others.
We wanted to examine if the newly developed MATRICS Consensus Cognitive Battery (MCCB) is useful in detecting differences between EOS patients and healthy controls, and to investigate if any areas of neurocognitive function in the EOS group were more impaired than others. Our results showed a general and explicit cognitive deficit in the patient group, with the area of executive function as the second least impaired domain, which was somewhat surprising. Consequently, we investigated whether this result could be due to lack 00of sensitivity in the MCCB’s measure of executive functioning, the Mazes test.
We chose to explore the properties of additionally two frequently used measures of executive function; the Stroop test and the Wisconsin Card Sorting Test (WCST) and compared them with the Mazes test. We found that the Mazes test performed well compared to the two other tests. Whether differences in EF between persons with EOS and AOS were as large as often thought, was our last study goal. In order to find out if executive function actually is more compromised in the EOS group, we investigated the two groups of patients adjusted for age and gender matched healthy controls on several EF measures. Our hypothesis was that the differences in EF between persons with EOS and AOS would be reduced after controlling for the level of EF in their respective, matched control groups. The hypothesis was confirmed: The adolescent patients do not perform significantly poorer than their adult counterparts on the domain of executive function.
In sum, our results show that the MCCB is suitable for use in adolescents with psychotic disorders, with the exception of the social cognition measure, the Mayor-Salovey- Caruso Emotional Intelligence Test (MSCEIT). The Mazes test included in the MCCB for measuring the area of executive function shows adequate sensitivity and discriminating power. If an elaboration of this domain is needed, the Stroop test is recommended as it discriminates even better between EOS patients and healthy controls. On the area of executive function, we found that after controlling for the levels of their age-matched controls, EOS patients do not perform significantly poorer than AOS patients.