Effects of an extrinsic motivator on the evaluation of cognitive and daily living functions in patients with schizophrenia
Introduction
Cognitive decline is one of the major symptoms of schizophrenia and is observed in various domains, including attention, executive function, and memory (Corigliano et al., 2014). Most patients with schizophrenia present with cognitive decline before the first episode, and then throughout the course of the disease (Basso et al., 1998). These cognitive symptoms are associated with the prognosis of schizophrenia and can persist even after improvement of other mental symptoms such as hallucinations and delusions (Rund, 1998).
Furthermore, cognitive symptoms are known to affect daily living function in patients with schizophrenia (Green et al., 2004). Decreased daily living function due to cognitive symptoms has been reported in patients with first-episode schizophrenia (Milev et al., 2005). Patients with schizophrenia face many difficulties when performing activities of daily living, such as the use of basic tools, using transportation, money management, eating, and cleaning (Patterson et al., 2001). In the rehabilitation of patients with schizophrenia, cognitive symptoms are considered to be a major predictor of work performance (Bryson and Bell, 2003). This impairment of daily living function not only impedes independent living, but can also cause socio-economic problems such as loss of occupational function (Rutman, 1994), increased management costs (Wu et al., 2005), and difficulty in rehabilitation treatment (Glynn, 2001).
Although therapeutic medications are continuously being developed, the recovery of cognitive and daily living function impairments in patients with schizophrenia remains unsatisfactory (Robinson et al., 2004); furthermore, patients with schizophrenia experience a deterioration in quality of life (Savilla et al., 2008). Therefore, the cognitive and daily living functionality in relation to schizophrenia treatment has garnered considerable interest, and many studies have assessed their evaluation methods (Green et al., 2008; Harvey et al., 2010; Nuechterlein et al., 2008).
An effective and ideal tool to test cognition and daily living function in patients with schizophrenia should comply with several criteria, including a sufficient reliability and validity, and the consistency of results across repeated assessments is especially important (Nuechterlein et al., 2008). However, behavior-based assessment tools can yield variable outcomes and largely depend on the condition of the examiner and subject. To overcome these limitations, examiners who implement such tests should be fully trained in advance and, if necessary, their reliability should be evaluated. Moreover, there is a necessity for constant control of the condition in patients with schizophrenia; however, this is often difficult in reality. Clinical symptoms such as depression and negative symptoms are known to impair cognitive and daily living functions (Berman et al., 1997; Ventura et al., 2009). Intraday variations might also exist, even with stable clinical symptoms; therefore, repeated examinations should be performed at the same time of day (Hufford et al., 2014). To minimize the effects of medication, such as anticholinergic effects, on the test results, the type and dose of medication should be controlled between the test and retest (Kim et al., 2019). Furthermore, the test schedule should be planned with consideration to the practice effect (Goldberg et al., 2007).
Moreover, the attitude of the subject being tested, i.e., their motivation or intention to conduct the test, is often overlooked; however, this is an important factor that might affect the test results. For example, in healthy subjects, it has been found that motivation can have a significant effect on cognitive function. Robinson et al. (2012) found that spatial memory and attention increased when healthy subjects were offered financial incentives. One study that assessed spatial attention found that attentional shifts were enhanced in healthy seniors when they were given incentives (Bagurdes et al., 2008). To our knowledge, there has not yet been an experimental comparison of the response of healthy subjects and patients with schizophrenia to an extrinsic motivator. According to a survey study by Gard et al. (2014), patients with schizophrenia are less responsive to external rewards than healthy subjects, and are more immersed in a disconnected-disengaged state. This could be because the motivation and reward system in patients with schizophrenia is impaired, which can often lead to difficulties in making meaningful, purpose-oriented actions or responding to external incentives (Choi and Medalia, 2010). This might involve various mechanisms, including dopamine-mediated basal ganglia system abnormalities, orbitofrontal cortex-driven impairments, aberrant effort-value computations, and altered activation of the prefrontal cortex (Strauss et al., 2014). The reduced intrinsic motivation of patients with schizophrenia compared to the general population might affect their neurocognition and psychosocial functioning (Nakagami et al., 2008). Intrinsic and extrinsic motivation have been reported to affect work outcomes in patients with schizophrenia who participate in employment programs (Reddy et al., 2016). Controlling these motivational factors prior to test administration might result in a more accurate assessment of the ārealā function of patients with schizophrenia, and thus improve the accuracy in treatment planning and determination of the treatment effect.
Therefore, we used the MATRICS consensus cognitive battery (MCCB) (Nuechterlein et al., 2008) and the UCSD Performance-based Skills Assessment (UPSA) (Patterson et al., 2001), which have high validity and reliability for the assessment of basic cognition and daily living functions in patients with schizophrenia, to identify the effect of an extrinsic motivator on the test results.
Section snippets
Subjects
We enrolled patients aged 18ā60Ā years who had been diagnosed with schizophrenia according to the diagnostic criteria of the Diagnostic and Statistical Manual of Mental Disorders fifth edition. All participants had been in rehabilitation since their symptoms had become stable, and had been receiving a constant dose of antipsychotics for the previous 3Ā months. To minimize the pure practice effect (between the first and second trial), we only enrolled patients who had already completed the MCCB
Demographic and clinical characteristics
We enrolled 60 participants (extrinsic motivator group: nĀ =Ā 30; control group: nĀ =Ā 30). In the motivator group, 25 patients received additional rewards for an increase in the retrial score compared to the baseline score. There were no significant between-group differences in sex, age, education level, duration of illness, or antipsychotic medication dose. There were no significant between-group differences in the AES, DAI, ISP, or SQLS scores related to psychosocial characteristics. Regarding
Discussion
We investigated whether an extrinsic motivator would affect the MCCB and UPSA scores in patients with schizophrenia. Our findings indicate that the extrinsic motivation did not induce a significant change in the UPSA score, which evaluates daily living function. However, the extrinsic motivator group showed a significant increase in the MCCB score, which indicates that motivation enhance cognitive function. Keefe et al. (2017) reported that the placebo response and practice effects of the MCCB
Disclosure statement
The authors have no financial benefit or interest to report.
Contributors
Do-Un Jung conducted the study protocol as primary principal investigator. Sung-Jin Kim wrote the first draft of the manuscript. Sung-Jin Kim and Dong-Wook Jeon designed the study, analyzed the data, drafted the manuscript, and participated the study protocol as the coinvestigator.
Young-Soo Seo, Sung-Soo Jung, Yoo-Chul Lee, and Jeong-Eun Kim conducted the study protocol as the co-investigator. Sung-Jin Kim and Jung-Joon Moon managed the literature searches and revised the manuscript critically
Role of the funding source
This work was supported by the 2017 Inje University research grant.
Declaration of competing interest
The authors declare no conflict of interest with any commercial or other associations in connection with the submitted article.
Acknowledgement
The authors thank staffs of the Sharing and Happiness Hospital and the Busan Metropolitan Mental Hospital for their assistance with the process of this study.
References (51)
- et al.
Reliability and validity of a depression rating scale for schizophrenics
Schizophr. Res.
(1992) - et al.
Modulation of the spatial attention network by incentives in healthy aging and mild cognitive impairment
Neuropsychologia
(2008) - et al.
Neuropsychological correlates of negative, disorganized and psychotic symptoms in schizophrenia
Schizophr. Res.
(1998) - et al.
Differential relationships between positive and negative symptoms and neuropsychological deficits in schizophrenia
Schizophr. Res.
(1997) - et al.
Intrinsic motivation and learning in a schizophrenia spectrum sample
Schizophr. Res.
(2010) - et al.
Neurocognition in schizophrenia: from prodrome to multi-episode illness
Psychiatry Res.
(2014) - et al.
Amotivation and functional outcomes in early schizophrenia
Psychiatry Res.
(2013) - et al.
Using self-determination theory to understand motivation deficits in schizophrenia: the āwhyā of motivated behavior
Schizophr. Res.
(2014) - et al.
Detecting reliable cognitive change in individual patients with the MATRICS Consensus Cognitive Battery
Schizophr. Res.
(2014) - et al.
Longitudinal studies of cognition and functional outcome in schizophrenia: implications for MATRICS
Schizophr. Res.
(2004)