What causes ADHD in adults?

Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder that often begins in childhood but can persist into adulthood. The exact causes of ADHD are still being researched, but studies suggest that genetics, environment, brain anatomy and neurotransmitter imbalances in the brain may all contribute to ADHD.

Table of Contents

Genetic Factors

There is strong evidence that genetics play a significant role in ADHD:

ADHD tends to run in families – if one family member has ADHD, there is a 25-35% chance that another immediate family member has it too.

The heritability of ADHD is around 70-80%, meaning that genetics accounts for about three-quarters of the risk.
Research has identified multiple genes associated with ADHD – although each individual gene variant only accounts for a small portion of risk.

The exact mechanisms behind how these genes influence ADHD development are still being investigated. However, many of the genes implicated are involved in regulating neurotransmitters like dopamine and serotonin in the brain – chemicals that are also targeted by ADHD medications.

Environmental Factors

While genetics play a clear role, they do not account for everything. Environmental factors, especially in early life, may interact with genetic vulnerabilities to influence ADHD risk. Potential environmental risk factors include:

Prenatal/Perinatal Problems: Exposure to toxins (e.g. lead), maternal stress, malnutrition, premature birth or low birth weight.
Traumatic Brain Injury: Especially in childhood – even mild injuries can alter brain development.

Chemical Exposure: Pesticides, heavy metals and other toxins may impact brain development.

However, more research is needed to clarify how strong the influence of these environmental factors is on ADHD specifically.

Brain Anatomy

Imaging studies reveal several anatomical differences in the brains of people with ADHD compared to those without:

Smaller overall brain volume, especially in the frontal lobe region.
Less activity in the frontal lobe – an area linked to “executive functions” like focus, planning and impulse control.
Reduced volume in, and weaker connections between, areas that make up cognitive control networks.

Delayed development of the cortex and lower cortical thickness.

It is unclear if these anatomical differences are a cause or a result of ADHD, but they may help explain some of the cognitive challenges faced in the disorder.

Neurotransmitter Imbalances

Several key neurotransmitters are implicated in ADHD:

Dopamine: Critical for motivation, reward pathways and motor control. Lower dopamine is linked to inattention and impaired reinforcement learning in ADHD.
Norepinephrine: Plays a role in alertness, focus and attention. Irregular norepinephrine activity is associated with distractibility and hyperactivity in ADHD.
Serotonin: Involved in mood, impulse control and social behavior. Disruptions to serotonin are more common in ADHD and may drive aggression and emotional dysregulation.

Genetic differences in dopamine and norepinephrine transporters and receptors likely contribute to these imbalances in ADHD. Environmental toxins and brain injuries can also alter neurotransmitter levels.

Interactions Between Factors

The development of ADHD likely involves complex interactions between many of these genetic vulnerabilities, environmental influences and resulting brain changes. A few key patterns of interaction may include:

Gene mutations make a child more sensitive to environmental risk factors like toxins or maternal stress.

Perinatal injuries coupled with genetic risks disrupt early brain development.
Genes regulating neurotransmitters are activated or suppressed by environmental influences.

However, more research is required to fully understand these interactions. The heterogeneity of ADHD itself also suggests there may be diverse causal pathways at play.

Other Potential Factors

A few other factors that may contribute to ADHD risk, but require more research include:

Gut bacteria – Differences in gut microbiome have been observed in those with ADHD and may interact with diet to influence symptoms.
Food additives – Some studies link consumption of processed foods with certain food coloring, flavoring and preservatives to worse ADHD behaviors.

Insufficient sleep – Poor sleep is common in ADHD and likely exacerbates issues with inattention and self-regulation.

Key Takeaways

The exact causes of ADHD are still being investigated, but research points to complex interactions between genetics, environment, brain anatomy and neurotransmitter activity.
ADHD is highly heritable, with genetics accounting for about 70-80% of risk.

Environmental factors like prenatal problems, toxins, injury and poor sleep may worsen genetic vulnerabilities.
Brain imaging reveals anatomical differences and atypical development in ADHD brains.
Imbalances in key neurotransmitters including dopamine, norepinephrine and serotonin are commonly observed.

There are likely diverse causal pathways leading to the heterogeneous symptoms of ADHD.
More research is needed to better understand the contributions and interactions between the many potential genetic, environmental and neurological factors.

The Diagnosis of ADHD in Adults

Getting an accurate diagnosis is the first step in managing ADHD in adulthood. However, this can be challenging for several reasons:

ADHD symptoms can be subtle and non-specific in adults compared to children.
Symptoms may be mistaken for other conditions like anxiety, depression or learning disabilities.
Standards and understanding of adult ADHD have evolved, even among health professionals.

Adults may mask or compensate for symptoms for years before seeking help.

There is no single, definitive test for ADHD. A comprehensive diagnostic process involves:

Screening questionnaires to assess common symptoms.

Clinical interview exploring symptom history, impact, and rule out other causes.
Collateral information from others who know the patient well.
Neuropsychological testing may sometimes be used.

Assessment for co-occurring conditions.

Diagnosis is based on the patient meeting DSM-5 criteria for ADHD presence and severity of symptoms, including:

Inattention – difficulty staying focused and organized.

Hyperactivity – excessive restlessness and activity levels.
Impulsivity – hasty actions without thought of consequences.
Symptom onset before age 12 years old (although this is being reconsidered).

Symptoms cause impairment in two or more settings/environments.

Ongoing symptoms must also be distinguishable from normal aging decline in focus, organization and memory.

Common Symptom Presentations

While ADHD symptoms persist into adulthood, their outward presentation often changes with age:

Children/Adolescents	Adults
Constant fidgeting	Inner restlessness
Running around, climbing excessively	Feeling driven to always be busy
Interrupting frequently	Impatience, trouble waiting turns in conversation
Difficulty playing quietly	Seeking high stimulation activities
Daydreaming in class	Trouble staying focused in lectures, while reading, etc.
Forgetting homework and chores	Missing deadlines, forgetting tasks and appointments
Difficulty following complex directions	Trouble learning and executing complex work tasks

Some adults with ADHD do still experience obvious hyperactivity, while others present more with inattentive symptoms. But most adults have a combined presentation of both types to some degree.

Getting Diagnosed as an Adult

The process of seeking a diagnosis and finding help for ADHD poses unique challenges for adults compared to children:

Stigma around mental health may deter adults fromseeking help.

Disorganization from ADHD itself can make booking appointments difficult.
Financial barriers like lack of insurance may prevent access to clinicians.
Adults need to self-identify their symptoms rather than parents or teachers.

Childhood history is important but can be hard for adults to accurately recall.

Some tips that can help adults navigate diagnosis and get the ADHD support they need:

Find a specialist – Look for psychologists or psychiatrists with expertise in adult ADHD diagnosis.

Check insurance coverage – See what diagnostic and treatment services are covered before making appointments.
Gather school records – Report cards, test scores or teacher comments can provide objective evidence of early symptoms.
Talk to family – Parents, siblings or childhood friends may recall ADHD signs from your youth.

Consider screening first – Self-screening tests can help motivate a full clinical assessment.

Treatment for Adults with ADHD

Effective treatment for ADHD typically involves medication, therapy, education, skills training and lifestyle adjustments. Treatment should be tailored to the individual’s needs and situation with a multimodal approach. Some key treatment components include:

Medication

Stimulants like Adderall, Ritalin, Vyvanse – Increase dopamine and norepinephrine.

Non-stimulants like Atomoxetine, Guanfacine – Alter norepinephrine and dopamine transmission.
Not a quick fix, but can greatly improve focus, motivation and impulse control when combined with other interventions.

Psychotherapy

Cognitive Behavioral Therapy – Changes negative thought and behavior patterns.

Mindfulness Based Therapies – Improves emotional regulation and focus.
ADHD Coaching – Provides organization and productivity strategies.

Education

Learning about ADHD helps adults make sense of symptoms and challenges.

Psychoeducation classes can teach coping techniques.
Improving ADHD knowledge empowers adults to manage their condition.

Skills Training

Organizational skills – Using planners, breaking down large tasks, managing time and clutter.

Communication skills – Listening carefully, clearly expressing needs, managing frustration and impulsivity.
Mindfulness and relaxation skills – Reducing anxiety, improving focus.

Lifestyle Adjustments

Healthy diet – Limiting sugar, increasing protein.

Regular exercise and sleep routine.
Reducing stressors and overstimulation when possible.
Structuring environment to minimize distractions.

Partnering Treatment Providers

Coordinating care between various professionals optimizes treatment success:

Primary Care Doctor – Coordinates referrals, monitors medication.
Psychiatrist – Assesses symptoms, prescribes and manages medications.

Therapist – Provides ongoing counseling and support.
ADHD Coach – Helps implement organization, time and stress management techniques.

Ongoing communication ensures various interventions complement each other. Support groups can provide community and motivation to keep implementing changes. A team-based approach, tailored to the individual, leads to the best ADHD treatment outcomes.

Coping Strategies for Adults with ADHD

In addition to formal treatment methods, adults can implement practical coping strategies in daily life to manage ADHD symptoms:

For Focus Issues

Use timers and alarms to stay on task.
Take regular movement or meditation breaks to recharge focus.

Minimize external distractions like email notifications.
Keep fidget tools like stress balls within reach.

For Organization Struggles

Use apps and calendars to track appointments and deadlines.

Make to-do lists or use bullet journals to organize tasks.
Tackle paperwork and filing regularly to avoid clutter accumulation.
Ask for written directions and instructions to minimize errors.

For Impulsivity Issues

Resist temptations and avoid triggers like malls or cafes.
Take time to consider consequences before acting.
Engage in interests and hobbies to channel impulses constructively.

Discuss high-risk behaviors honestly with care providers.

Using strategies like these consistently, even if progress is gradual, helps adults manage the impact of ADHD challenges.

The Importance of Support Systems

Given the chronic, impairing nature of ADHD, establishing personal and professional support systems is essential:

Family & Friends

Provide understanding, encouragement and flexibility.
Offer reminders and assist with organization.
Give honest feedback when you notice symptoms worsening.

Coworkers & Employers

Make reasonable accommodations like noise-cancelling headphones, flexible deadlines or working from home options.
Allow use of apps, tools and systems that compensate for weaknesses.
Provide written job instructions, performance feedback and reminders.

Professional Supports

Participate in ADHD coaching and psychotherapy.
Join adult ADHD support groups.
Hire assistants to help with tasks like scheduling and paperwork.

Seeking understanding and support can make the difference between discouragement and successfully adapting to live with adult ADHD.

Conclusion

ADHD arises from complex interactions between genetic vulnerabilities, brain development and environmental influences. While exact causes are still unclear, research continues to uncover the neurological, chemical and anatomical factors underlying ADHD.

Seeking an accurate diagnosis and tailored, multimodal treatment enables adults with ADHD to minimize symptoms and thrive. By implementing lifestyle changes, practical strategies and support systems, adults can adapt and overcome the challenges of ADHD.