Handwriting movements for assessment of motor symptoms in schizophrenia spectrum disorders and bipolar disorder

RESEARCH ARTICLE Handwriting movements for assessment of motor symptoms in schizophrenia spectrum disorders and bipolar disorder Yasmina Crespo ID1,2☯*, Antonio Ibañez1☯, Marı́a Felipa Soriano2☯, Sergio Iglesias1☯, Jose Ignacio Aznarte2☯ 1 Psychology Department, University of Jaén, Jaén, Spain, 2 Mental Health Unit, St. Agustı́n Universitary Hospital, Linares, Jaén, Spain a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 OPEN ACCESS Citation: Crespo Y, Ibañez A, Soriano MF, Iglesias S, Aznarte JI (2019) Handwriting movements for assessment of motor symptoms in schizophrenia spectrum disorders and bipolar disorder. PLoS ONE 14(3): e0213657. https://doi.org/10.1371/ journal.pone.0213657 Editor: Vincenzo De Luca, University of Toronto, CANADA Received: September 24, 2018 Accepted: February 26, 2019 Published: March 14, 2019 Copyright: © 2019 Crespo et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. ☯ These authors contributed equally to this work. * Abstract The main aim of the present study was to explore the value of several measures of handwriting in the study of motor abnormalities in patients with bipolar or psychotic disorders. 54 adult participants with a schizophrenia spectrum disorder or bipolar disorder and 44 matched healthy controls, participated in the study. Participants were asked to copy a handwriting pattern consisting of four loops, with an inking pen on a digitizing tablet. We collected a number of classical, non-linear and geometrical measures of handwriting. The handwriting of patients was characterized by a significant decrease in velocity and acceleration and an increase in the length, disfluency and pressure with respect to controls. Concerning non-linear measures, we found significant differences between patients and controls in the Sample Entropy of velocity and pressure, Lempel-Ziv of velocity and pressure, and Higuchi Fractal Dimension of pressure. Finally, Lacunarity, a measure of geometrical heterogeneity, was significantly greater in handwriting patterns from patients than from controls. We did not find differences in any handwriting measure on function of the specific diagnosis or the antipsychotic dose. Results indicate that participants with a schizophrenia spectrum disorder or bipolar disorder exhibit significant motor impairments and that these impairments can be readily quantified using measures of handwriting movements. Besides, they suggest that motor abnormalities are a core feature of several mental disorders and they seem to be unrelated to the pharmacological treatment. Data Availability Statement: All data files are available from the figshare database (https:// figshare.com/articles/DataRepository_sav/ 7117178). Introduction Funding: This study was funded by Junta de Andalucı́a (Biomedical and Heath Science research project: PI-0410-2014 to MFS and PI-0386-2016 to SI). The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. Motor abnormalities (MA) are a relevant feature of several mental disorders [1]. MA have been widely studied in schizophrenia, from early descriptions of the disorder [2]. Later, with the discovery of antipsychotic drugs, MA were mainly studied as side effects of the pharmacological treatment. Nevertheless, recent research has shown a renewed interest in the study of MA in schizophrenia. It has been suggested that spontaneous and medication- independent PLOS ONE | https://doi.org/10.1371/journal.pone.0213657 March 14, 2019 1 / 18 Handwriting movements for assessment of motor symptoms in schizophrenia spectrum and bipolar disorder Competing interests: The authors have declared that no competing interests exist. motor phenomena can represent a specific dimension within the schizophrenia-spectrum [3]. MA have been detected in antipsychotic naïve patients with a first psychotic episode and even in individuals at high risk of psychosis [4–7]. Furthermore, MA have been observed in studies with children who later developed schizophrenia [8–12], as well as in chronic patients who had never been medicated [13]. These results seem to imply that MA have a central role in the prognosis and evolution of the disease and it has been signaled that they could facilitate accurate early detection and tailored intervention [14]. MA have been less studied in bipolar disorder. However, a wide amount of research has highlighted the commonalities between schizophrenia spectrum disorders and bipolar disorder [15–19]. Both disorders share genetic liability and some clinical features [20]. It has been shown that cognitive deficits and functioning is similar in early-onset schizophrenia and early-onset bipolar disorder, suggesting that cognitive dysfunction is more related to the neurodevelopmental course of the disorder than to the specific diagnosis [21]. Joined together, these results have led to a debate about whether schizophrenia spectrum disorders and bipolar disorders belong to different diagnostic categories, or to a common psychotic-affective spectrum [22]. Recent research has shown that certain cognitive and biological measures allow for better characterization of subtypes of patients with schizophrenia, schizoaffective and bipolar disorders than classical diagnosis methods [23]. MA could be a core characteristic in disorders within this spectrum. However, as we mentioned before, few studies have explored motor symptoms in bipolar disorder. For example, [24] found that patients with bipolar disorder performed worse on some measures of motor function [force steadiness and velocity scaling] than healthy participants. Furthermore, in a study from [25], with elderly people suffering from bipolar disorder, this group showed higher prevalence and increased severity of extrapyramidal symptoms [measured with observer-based rating scales] than controls. These findings were not associated with duration of illness or with current pharmacological exposure. More interestingly, [26] assessed motor performance in children of 7 years of age of parents with schizophrenia or bipolar disorder. They found that children of parents with schizophrenia showed significantly impaired motor performance compared to control children. On the contrary, there were no significant differences between children of parents with bipolar disorder and control children. Motor performance in children at risk of bipolar disorder was somewhat intermediate between children at risk of schizophrenia and control children. In short, MA could have an essential role in the diagnosis of schizophrenia spectrum disorders and bipolar disorders. The inclusion of a motor domain would allow a better understanding of psychopathology, and may also reveal important contributions to disease proc (...truncated)