Unraveling the Genetic Code of Bipolar Disorder

In a recent study published on medRxiv* preprint server, researchers are studying genetic associations and heritability between categorical and dimensional bipolar disorder (BD) models.

Study: Strong genetic overlaps between dimensional and categorical patterns of bipolar disorder in a familial sample. Image Credit: My Ocean Production / Shutterstock.com

*Important Notice: medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be considered conclusive, guide clinical practice/health-related behaviors, or treated as established information.

What is BD?

BD is a mental health disorder characterized by cyclical swings between depressed and manic mood and behavioral states that make it difficult to function and perform daily activities. According to recent estimates, 2-4% of adults in the United States will experience comics at some point in their lives. It is important to note that BD is often misdiagnosed or unrecognized for years after the initial onset of symptoms.

Subclinical symptoms of BD that do not meet definitive diagnostic standards affect many people. As a result, there is now more emphasis on dimensional assessments of psychopathology like the Mood Disorders Questionnaire (MDQ) that can better describe the full spectrum of symptoms of BD.

Despite the high prevalence of BD, little is known about the underlying environmental and genetic variables that cause this condition. Previous studies indicate that BD is highly heritable, with estimates ranging from 60-85%. Nevertheless, there is little information regarding genetic and heritability relationships between categorical and dimensional BD models.

About the study

In the current study, the researchers assess the genetic continuity between categorical and dimensional BD models. For this purpose, data from the Amish-Mennonite Bipolar Genetics (AMBiGen) study, which includes families with TB and related disorders from Mennonite and Amish communities in South and North America, were used.

Structured psychiatric interviews were conducted, during which study participants were asked to complete the MDQ assessing life history of cardinal manic symptoms and associated impairments.

A total of 726 people were included in the current study, 212 of whom had a definite diagnosis of a major mood disorder. An essential tool has been created to assess heritability that integrates genomic data and the genomic relationship matrix (GRM) using high-quality single nucleotide polymorphism (SNP) information.

A principal component analysis (PCA) was performed to assess the dimensions of the MDQ. Genetic overlaps and heritability between categorical diagnoses and MDQ-derived measures were estimated among genotyped participants.

The objective of the present study was to validate the MDQ as a dimensional assessment of BD and to better understand the environmental and genetic variables that contribute to the development of this disorder. These findings could have a huge impact on how TB and related diseases are diagnosed, treated and prevented.

Study results

Significant genetic overlaps were observed between categorical and dimensional BD patterns within a family sample. Additionally, study participants diagnosed with BD possessed higher MDQ scores than those without a BD diagnosis, demonstrating the reliability of MDQ as a dimensional measure of BD.

Strong genetic connections and considerable heritability were observed for most components of MDQ, thus reflecting that categorical and dimensional measures of BD have significant genetic overlap.

The MDQ assesses three characteristics, including depressive symptoms, manic symptoms, and impairment. The MDQ symptom score had a heritability of 30% and was evenly distributed among its three main components.

Categorical diagnoses and impairment had the strongest genetic associations, indicating that impairment may contribute significantly to genetic continuity between categorical and dimensional models of BD.

conclusion

The results of the study indicate genetic continuity between categorical and dimensional patterns of BD in a family sample. These results suggest that the MDQ could be a valuable tool in determining those at risk for TB and other associated disorders.

In addition to providing valuable information about the environmental and genetic elements influencing BD and similar diseases, the study results may improve the accuracy of prevention, treatment and diagnosis of BD and related disorders.

Additionally, future studies of the genetic continuity between categorical and dimensional models of psychiatric illnesses could benefit from the methods and results discussed in this study. The study results may also support the development of more effective treatments for psychiatric disorders by providing a better understanding of the environmental and genetic components that contribute to these diseases.

*Important Notice: medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be considered conclusive, guide clinical practice/health-related behaviors, or treated as established information.