Neurological Soft Signs Of Schizophrenia Are Highly Heritable

Research shows that soft signs such as rigidity, gait imbalance and tremors are an inheritable indicator of schizophrenia.

AsianScientist (Oct. 6, 2015) – When it comes to making a diagnosis of schizophrenia neurological soft signs (NSS) such as rigidity, gait imbalance and tremors are thought to be associated with the disease but not used due to a lack of specificity and validation.

However, researchers from the Institute of Psychology of the Chinese Academy of Sciences have now found that NSS is indeed robustly inheritable and significantly correlated with schizophrenia. The results, published in Psychological Medicine, suggest that NSS could be a promising biomarker for schizophrenia.

Dr. Raymond Chan’s team from the Institute of Psychology of Chinese Academy of Sciences and his international collaborators conducted a study to examine the heritability and familiality of NSS in the Han Chinese population. They adopted a healthy twin design and combined this method with clinical patients and their non-psychotic first-degree relatives.

Using the abridged version of the Cambridge Neurological Inventory, 267 pairs of monozygotic twins, 124 pairs of dizygotic twins, and 75 pairs of patients with schizophrenia and their first-degree relatives were examined for their NSS performances. The classical method and structure equation model analysis were then used to examine the heritability and familiality of NSS in their participants.

The results showed that NSS were robustly heritable in the healthy twins sample, especially for the items relating to the motor coordination and sensory integration (with heritability of 0.5-0.6). Their findings also showed that patients with schizophrenia correlated significantly with their first-degree relatives on NSS.

It should be noted that the heritability of NSS they found in both healthy twins group and patient-relative pairs group were comparable to those reported by the Consortium on the Genetics of Schizophrenia (COGS), around 0.3-0.4. The COGS is an international consortium specifically established for the study of endophenotypes for schizophrenia.

Given the brevity of NSS administration compared to conventional neurocognitive assessment, NSS are informative endophenotype and have been incorporated into the assessment regime for schizophrenia in the early psychosis program jointly run by Chan and Drs. Eric Cheung and Simon Lui from Castle Peak Hospital in Hong Kong.

NSS are also the key elements of the Consortium for the Human Information and Neurocognitive Endophenotype (CHINE) established by Chan. The CHINE is intentionally established to pave the roadmap for neuropsychiatric disorders research. It not only identifies the biosignatures for neuropsychiatric disorders, but also serves as the central databank for examining the etiologies of major complex neuropsychiatric disorders and serving as the main basis for corresponding treatment development.

The article can be found at: Xu et al. (2015) Heritability and Familiality of Neurological Soft Signs: Evidence from Healthy Twins, Patients with Schizophrenia and Non-Psychotic First-Degree Relatives.


Source: Chinese Academy of Sciences; Photo: Shutterstock.
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