A meta-analysis of the genetics of tic disorders shows that this overlaps with the genetics of several other psychiatric disorders and that one gene may be promising to study in more detail to find a cure for tic disorders.
Tic disorders are often overlooked, especially among young boys, who develop sudden and involuntary movements such as blinking, wrinkling their nose, sniffing or coughing. Fortunately, this is often transient.
However, tic disorders continue for some people, who may struggle with it for the rest of their lives.
An international group of researchers has investigated the genetic characteristics of people who have tic disorders, and these characteristics overlap with those of other psychiatric disorders and specific genetic variants may contribute to the development of tic disorders.
The researchers hope that the research, which is still in its early stages, will improve understanding of tic disorders and provide more knowledge about how they are linked to other psychiatric disorders and how to treat them.
“Tic disorders are insufficiently studied, and this is the first study of its kind that is large enough to begin investigating genetic associations between tic disorders and other psychiatric disorders and somatic diseases. It is not a comprehensive and groundbreaking study, but it is an important step forward,” explains a researcher behind the study, Jakob Grove, Professor, Department of Biomedicine, Aarhus University, Denmark.
The research has been published in Biological Psychiatry.
Understanding genetics may make diagnosis easier
Studies of genetics have yielded new and revolutionary knowledge in many psychiatric disorders.
Genetic studies have made researchers more aware of why various psychiatric disorders arise, and for some psychiatric disorders, medicine has begun to be developed based on genetic discoveries.
This applies to treatment for schizophrenia, and researchers are conducting trials with new and promising drugs.
Jakob Grove says that, in its simplest form, genetic research may identify a defective gene that leads to a defective protein that influences a disease or disorder and that targeting this protein with medicine may restore its function and thus treat the disease or disorder.
However, reality is often much more complicated than this, and the researchers in this study took the first step in discovering the complications.
“The initial goal is to determine the genetic characteristics of people with tic disorders to enhance diagnosis. This will make it much easier to determine whether people have a tic disorder or something else,” says Jakob Grove.
Genes from nearly 1 million people
The researchers analysed the genomes of 9,619 people with tic disorders and 981,048 controls to find small variations between people in the structure of genes.
Discovering a general association between genetic variants and a given phenotype, such as tic disorders, indicates that the variants and thus the associated genes influence that phenotype: thus, many people with tic disorders have the same genetic variants.
“This does not confirm the effects or lack thereof of specific variants, but we can determine whether some variants are guilty by association,” notes Jakob Grove.
Genetic overlap with other psychiatric disorders
Although the study is an early one of its kind, it suggests that one specific location on the genome is a variant of a genetic mutation associated with the development of tic disorders.
Jakob Grove says that the association is not yet very strong, but someone could continue the research and investigate which gene the genetic variant is located in and whether this should be investigated further to understand tic disorders.
According to Jakob Grove, the most interesting thing about the study is that the researchers found a genetic overlap between the genotype of tic disorders and the genotype of other psychiatric disorders such as schizophrenia and bipolar disorder.
This means that, broadly speaking, the genetic landscape of people with tics is similar to the genetic landscape of people with various psychiatric disorders.
“This is interesting because it indicates that we are on the right track. It is also recognisable from clinical experience, with tic disorders often being comorbid with other psychiatric disorders,” explains Jakob Grove.
More knowledge about the biology behind tic disorders
Jakob Grove explains that, although the study is not a game-changer in understanding tic disorders, it will nevertheless add significantly to the major databases of the genetics behind various disorders.
These large databases collect all genetic information about various diseases and disorders and have lacked information about tic disorders.
This means that researchers can now relate genetics to other disorders and identify which genes are associated with people developing tic disorders.
Jakob Grove emphasises that the large databases do not contain data on individuals, since this would be personally identifiable information.
“The statistical results from the study will, in turn, contribute to the large databases of genetic variants and their relationship to diseases and disorders, in which information about tic disorders has been lacking. The long-term perspective is improving diagnosis and treatment, but in the short term the aim is to improve understanding of the underlying biology and which signalling pathways are involved,” concludes Jakob Grove.
