A researcher is investigating the heritability of a specific psychological trait. They compare the concordance rates—the likelihood that if one sibling has the trait, the other does too—across different types of sibling pairs. If this trait has a strong genetic basis, similar to the findings for certain neurodevelopmental disorders, which group would be expected to show the highest concordance rate?

The significant role of genetics in ADHD is supported by twin and adoption studies. A comprehensive 2009 review by Burt revealed that the median concordance rate for identical twins was .66, substantially higher than the .20 rate for fraternal twins. The same review identified a concordance rate of .09 for unrelated adoptive siblings, suggesting that while genetics are primary, environmental factors may also contribute to the disorder's development.

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Attention-Deficit Hyperactivity Disorder (ADHD) is characterized by inattention and hyperactivity-impulsivity and is divided into three subtypes:
- primarily inattentive
- primarily hyperactive-impulsive
- combined

Attention-Deficit Hyperactivity Disorder (ADHD)

Spielman, R. M., Jenkins, W. J., & Lovett, M. D. (2020, April 22). Psychology (2nd ed.). OpenStax. https://openstax.org/books/psychology-2e/pages/1-introduction

OpenStax Psychology (2nd ed.) Textbook

Inattention in children can manifest in bad time management, forgetfulness, disorganization, and task avoidance; while hyperactivity can manifest in ways such as difficulty waiting for their turns, difficulty in being still, excessive physical activities such as running and climibing. 

ADHD in Childhood

The exact causes and triggers for ADHD development are unknown, but there are some speculated risk factors. 

ADHD is NOT caused by excess sugar, poor parenting/schooling, too much TV/video games, stress, or food allergies. These things may make symptoms worse, but they are NOT causes.

Causes of ADHD

Sections:
- Prevalence in Children and Adolescents
- Prevalence in Adults
- Prevalence by Gender
- Prevalence by Race/Ethnicity
- Prevalence within Families

ADHD: Prevalence Rates

According to the DSM-V, diagnostic criteria for ADHD is as follows:
- A persistent pattern of inattention and/or hyperactivity-impulsivity that interferes with functioning or development.
- Several inattentive or hyperactive-impulsive symptoms were present prior to age 12 years.
- Several inattentive or hyperactive-impulsive symptoms are present in two or more settings (e.g., at home, school, etc.)
- There is clear evidence that symptoms interfere with, or reduce the quality of social, academic, or occupational functioning.
- The symptoms do not occur exclusively during the course of schizophrenia or another psychotic disorder, and are not better explained by another mental disorder.

ADHD: Diagnostic Criteria

Symptoms are grouped into 3 types:

- Inattentive: easily distracted, forgetful, daydreams frequently, and disorganized.
- Hyperactive-Impulsive: fidgety, excitable, high-energy, struggles with patience, interrupts others
- Combined: displays a mix of symptoms from the above two types.

Symptoms can change as a person grows and develops, and some even "grow out of their ADHD".  It is possible for symptoms to disappear or resurface during one's lifetime.

Symptoms of ADHD

Those diagnosed with ADHD often find that their ADHD diagnosis impacts the strength and stability of their relationships. Some examples of potentially affected relationships include childhood friendships, familial relationships, romantic partnerships, and relationships with oneself.

Relationships and ADHD

Considering the abundance of pediatric diagnoses, with a large increase since diagnostic changes in the 1980s and changes in Medicare coverage, this disorder's diagnosis has been met with a fair amount of criticism. Particularly regarding pediatric diagnosis, many critics claim ADHD is over-diagnosed, assigning a disability to a child simply being a child and medicating them to enforce compliance. Some critics proclaim this increase in medication of children for ADHD is to push drugs on the population and make a buck. 
Over-prescribing does exist in some areas, however, on the whole, it does not appear to be the case. Not every individual with ADHD is prescribed medication. Just because diagnoses have increased, doesn't mean they're all false positives. Diagnostic criteria has changed as our understanding of the disorder has changed. Though this is still hotly debated, additional research is encouraged to formulate an opinion. 

ADHD Diagnosis Controversies

Though there is no cure, there are treatments to help manage symptoms. There are two types of treatment options for ADHD:

- Behavior Therapy (including parental training).
- Medication.

Like most treatments for mental disorders and psychological issues, the best treatment is often a combination of therapy and medication. 

For children with ADHD younger than 6 years old, parent training in behavior management  is recommended as the first line of treatment, before medication is tried. For children 6 years old and older, it's recommended to try medication and behavior therapy together.

ADHD: Treatment Options

There are three diagnostic types of ADHD:
- Inattentive Type (Formerly known as Attention-Deficit Disorder)
- Hyperactive-Impulsive Type
- Combined Type (exhibits symptoms of both Inattentive type and Hyperactive/Impulsive type)

ADHD: Types

- Children
- Adults
- College Students
- Parents of Children with ADHD

Experiences of ADHD by Population Group

Though there is no cure, there are treatments to help manage symptoms. Like most treatments for mental disorders and psychological issues, the best treatment is often a combination of therapy and medication. For children with ADHD, therapy is often recommended for their parents/guardians so they know how to better handle the symptoms their child manifests. 

Regarding medications, stimulants are the most frequently prescribed. However, other kinds are prescribed, as stimulants don't work for everyone.

- Stimulants
- Non-stimulants
- Anti-depressants

ADHD Treatment

The MTA (1999) was a study aiming to evaluate the effectiveness of ADHD treatments for children. The study was conducted over a 14-month period.

- ADHD treatments evaluated by the MTA
- MTA participant selection
- Major Findings of the MTA 
- Limitations of the MTA
- MTA: after the study
- MTA research sites
- MTA references

Multimodal Treatment of Attention Deficit Hyperactivity Disorder (MTA) Study

Research suggests that ADHD-related impairment results from deficits in one or more of several neurological processes, including:
 - Response inhibition and Working memory ("Cool" executive functioning)
 - Delay Aversion ("Hot" executive functioning)
 - Temporal Processing and Cognitive-energetic state

Etiology of ADHD

- Depression
- Anxiety Disorders
- Bipolar disorder
- SUDs (Substance-Use Disorders)
- Personality Disorders

ADHD: Common Psychiatric Comorbidities

In the 1920s, Hans Hoffman provided one of the earliest documented descriptions of symptoms now associated with ADHD. While caring for his son, Hoffman observed behaviors such as a short attention span, difficulty concentrating on schoolwork, and the need for repeated review of simple material to learn it.

Hans Hoffman's Early Observations of ADHD Symptoms

The modern concept of ADHD formed from the realization that hyperactivity (fidgetiness, restlessness, poor impulse control) and inattention (distractibility, concentration issues) were often co-occurring symptoms. This understanding solidified in the 1970s and led to the inclusion of 'attention deficit disorder with and without hyperactivity' in the DSM-III in 1980, establishing the foundation for the current diagnosis.

Evolution of the ADHD Diagnosis in the DSM

For a significant portion of individuals, ADHD is a lifelong condition that persists into adulthood for about 60% of diagnosed children. This persistence is strongly associated with a high rate of other mental health conditions. A study revealed that nearly 81% of adults with persistent ADHD also had at least one comorbid disorder, a rate substantially higher than the 47% found in adults whose childhood ADHD did not persist.

ADHD Persistence and Comorbidity in Adulthood

Evidence for Genetic Influence on ADHD from Twin and Adoption Studies

The heritability of ADHD's core symptoms is estimated to be very high, reinforcing the disorder's strong genetic roots. A 2010 review of studies by Nikolas & Burt found that the heritability of inattention was 71%, while the heritability of hyperactivity was 73%.

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