Genetic And Hereditary Aspects Of Dyscalculia

Introduction

Dyscalculia is a specific learning disability where a person has persistent difficulty learning, understanding, or using maths. Contrary to common misconceptions, individuals with dyscalculia often have normal or above-average intelligence. Approximately 5% of people are affected by dyscalculia, which is caused by a combination of genetic and environmental factors.

Developmental dyscalculia, in particular, is a hereditary learning disability. Over the past quarter-century, a growing body of evidence has supported the hypothesis that this inherited characteristic is nearly 10 times more likely to be found in families than in the general population.³ This disability is linked to abnormalities in brain structures responsible for numerical processing, where genetic mutations associated with these brain structures can be passed from parent to child.¹⁰

Types of dyscalculia

Dyscalculia is generally classified into two main categories:^2,6 developmental and acquired, each with distinct causes and characteristics. Understanding the differences between these types is crucial for tailoring interventions, as the underlying causes and potential treatments vary significantly.

Developmental dyscalculia

Primary developmental dyscalculia: This type originates from innate delays or deficiencies in the brain's ability to process numerical magnitudes.² It often manifests early in childhood and can affect the foundational understanding of numbers, quantities, and mathematical operations. Children with this condition may struggle to grasp concepts like counting, comparing quantities, or understanding numerical relationships, regardless of adequate teaching or environmental support.²

Secondary developmental dyscalculia: Unlike the primary form, this type results from external or environmental influences.² Factors such as poor teaching quality, low socioeconomic conditions, limited exposure to numerical activities, short attention spans, or domain-general cognitive deficits can lead to significant difficulties in learning mathematics. While these challenges are often reversible with appropriate intervention, they highlight the importance of supportive learning environments and early detection.

Acquired dyscalculia

Acquired dyscalculia occurs later in life, typically following a significant event such as a traumatic brain injury, stroke, or illness that affects brain function.⁶ Unlike developmental dyscalculia, individuals with this condition may have had normal mathematical abilities earlier but experience a sudden or gradual decline due to the injury or illness. This type can severely disrupt daily life, as numerical reasoning and problem-solving are critical for managing finances, time, and other essential tasks.⁶

Overview of the causes of dyscalculia

There are many different causes of dyscalculia and the causes vary between individuals. Genetic, environmental, and gene-environment interaction are all contributing factors to dyscalculia. 

For primary developmental dyscalculia, the main cause is found to be deficits or abnormalities in the brain structures and functions involved in numerical processing.¹⁰ For example, the poor sense of numbers is linked to the function of the left intraparietal sulcus, which processes numerical data, and the frontal lobe, which is responsible for reasoning.¹ These neural deficits or abnormalities often have a significant genetic and hereditary basis. 

Genetic basis of dyscalculia

Twin studies demonstrate the high specific heritability of dyscalculia. A genetic analysis of a study group composed of 1500 pairs of monozygotic and 1375 pairs of dizygotic 7-year-old twins revealed that 30% of the genetic variance is related to mathematical abilities.⁴  In particular, chromosomes 6 and 15 play important roles in the aetiology of developmental dyscalculia.³ 

Further family studies have shown a significant genetic contribution to the aetiology of developmental dyscalculia. In the late 1990s, Gross-Tsur et al. conducted a demographic study which indicated that 10% of children with developmental dyscalculia (DC) had at least one other family member who required help in mathematics, and 45% had a family member with a different learning disability.⁵

These findings led Shalev RS et al. (2001) to investigate the familial aggregation of developmental dyscalculia (DC).³ In their sample of 39 children with DC, they found that  66% of mothers, 40% of fathers, 53% of siblings, and 44% of second-degree relatives had DC.³

Other known genetic causes of dyscalculia include: 

• Turner’s syndrome
• Fragile X syndrome
• Velocardiofacial syndrome
• Williams syndrome

Identifying the genes

Gene-finding strategies

Following the collection of evidence supporting the existence of a genetic component in dyscalculia,  gene-finding strategies are carried out to identify the candidate genes.⁷ The main gene-finding strategies are genome-wide association studies (GWAS), genome-wide linkage analysis (GWLA), and association studies done on comorbidities.⁷

Next, the researchers seek additional evidence using methods including replicating association studies, mutation screening, and studying RNA and protein expression patterns.⁷

Challenges in identifying the genes

Although the genetic and hereditary nature of dyscalculia has been recognised, research progress into the genetic mechanisms behind the learning disability is impeded by the complexity of the phenotype.⁷ Cultural, cognitive, socioeconomic, linguistic, emotional, and motivational factors can all affect the phenotype.⁷ Discerning the role of genetic components responsible for mathematical ability from other influencing factors is challenging.⁷

Despite these difficulties, understanding the underlying cellular and molecular processes of specific patterns of impairment is crucial for developing effective teaching interventions that target critical conceptual activities.^4,7 

Environmental causes of dyscalculia

Besides genetics, dyscalculia can result from:

• alcohol consumption during pregnancy 
• taking drugs during pregnancy without consultation 
• availability of mathematics resource materials at home
• method of instruction at school
• irregular school attendance

Gene-environment interaction

Gene-environment interaction describes how an individual's observable characteristics, which are determined by their genetic constitution, interact with environmental factors. In genetic research, it is important to consider the effects of gene-environment interaction.

An individual’s mathematics performance is influenced by genetic factors and closely linked to their attitudes and emotions towards mathematics. A good example is the variation in motivational levels for engaging with mathematics observed in children. Children who struggle with math anxiety tend to have lower levels of motivation to engage with mathematics.⁹ On the contrary, children with a genetic predisposition for strong mathematical abilities may show more motivation and engagement with mathematical tasks.⁹ Common coexisting or co-occurring conditions:

• Dyslexia
• Dyspraxia
• Attention deficit and hyperactive disorder (ADHD)
• Specific language impairment 

Symptoms and diagnosis criteria

Symptoms of dyscalculia may include:³

• Difficulty with fractions and decimals
• Difficulty with long-division
• Difficulty with multiplication and multiplication tables
• Difficulty with money and time
• Trouble understanding mathematical terms and language
• Difficulty comparing the magnitude of numbers
• Difficulty placing things in order
• Difficulty identifying small quantities
• Notable disparity between arithmetic achievement and IQ

However, it is important to note that there is a significant variability in the presentation of symptoms and the level of severity between individuals with dyscalculia.²

Diagnosis of dyscalculia

If dyscalculia is suspected, a thorough diagnostic evaluation is necessary to account for the complexity of this learning disorder and to accurately identify the affected child’s specific strengths and weaknesses in arithmetical skills.⁴

Healthcare providers diagnose the disorder based on the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders (DSM-5) criteria. Other possibilities that may have caused the symptoms, such as visual impairment, audio impairment, and other mental disorders are also eliminated.

Why is the diagnosis and management of dyscalculia important?

Early detection and treatment of dyscalculia are crucial for achieving the best outcomes.⁶ Moreover, dyscalculia is often associated with mental health issues like anxiety and depression, which can contribute to self-doubt and lack of self-worth in affected individuals.⁸ Affected children often develop a negative attitude towards mathematics, which may manifest into mathematics anxiety or a fear of school.⁶

Effects of dyscalculia 

Dyscalculia affects individuals' daily lives and career prospects while also posing broader challenges to national productivity and education systems. 

Dyscalculia impacts individuals by creating challenges in education, daily life, and career opportunities, often affecting confidence and mental health. For individuals, underachievement in mathematics can significantly impede their ability to reach their full academic and non-academic potential.⁴

On a national scale, it can reduce productivity and increase education-related costs, highlighting the need for effective interventions. For nations, poor numerical skills have been shown to reduce GDP growth and carry a significant financial cost to governments.⁴ For example, the estimated annual cost of low numeracy to the UK is £2.4 billion.⁴

Treatment and management of dyscalculia

There is currently no cure for dyscalculia.⁶ However, with appropriate remedial interventions and guidance provided by caretakers and special education teachers, individuals with dyscalculia can overcome their difficulties. Treatment may involve:⁴

• Personalised learning applications
• Use of adaptive software
• Psychotherapy
• Medication

FAQs

What is the difference between dyscalculia and dyslexia?

Dyslexia affects language skills, whereas dyscalculia affects arithmetic skills. 

Can an individual have dyscalculia and dyslexia simultaneously?

Yes, around 40% of people with dyslexia also have dyscalculia.¹¹

Can we assess the risk of dyscalculia in children via genetic screening?

It is currently beyond our grasp for genetic screening to become a way to assess dyscalculia risk early in children before difficulties with mathematics become evident.⁷ The use of genetics to distinguish normal and abnormal brain development still needs to be better understood and developed.⁷

Does dyscalculia improve without treatment?

Dyscalculia does not improve without treatment.⁸

Summary

Dyscalculia is a specific learning disability affecting approximately 5% of the general population and can have lifelong consequences for individuals. Developmental dyscalculia has a strong genetic and hereditary basis, making it more likely to run in families. While identifying the specific genetic components remains challenging, such research could significantly enhance our understanding of this condition and lead to the development of more effective teaching strategies. Early diagnosis is crucial for managing dyscalculia. Although it cannot be cured, targeted interventions involving caregivers and special education specialists can help individuals overcome many of the associated challenges.