ADHD is defined by 18 core symptoms across three categories: inattention, hyperactivity, and impulsivity. While the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) provides a framework for diagnosing ADHD, its criteria are heavily based on behaviours observed in boys decades ago. This can make it more challenging to identify ADHD in adolescents and adults, girls and women, where the manifestations of these symptoms evolve with age and life demands. This can also lead to adults dismissing ADHD as a possibility because their view of ADHD is of hyperactive little boys, which does not map well onto their possible experienced symptoms of procrastination, distraction, memory problems, and feelings of chronic overwhelm.
When the DSM-5 was released in 2013, several changes were made to help the criteria fit more with adults, such as requiring fewer symptoms and adding more adult examples to a few items. However, this was all done on expert consensus rather than evidence-based (which is how most disorder criteria are decided), and so the suitability of these changes to help with diagnosis could only be guessed at.
This post looks at how symptoms can change developmentally from childhood to adulthood and underlines why different criteria could be useful for moving ADHD understanding and assessment into the 21st century.
Inattention: A Lifelong Struggle with Focus and Organisation
In Childhood
Inattentive symptoms often manifest in the classroom and at home, where sustained focus and following instructions are critical. These symptoms are harder to detect in preschool children. Preschool children are the group with the highest rate of hyperactive-impulsive presentation ADHD because of this. It is a presentation that is rare above this age group. Common behaviours include:
Difficulty paying attention to details, leading to careless mistakes.
Trouble staying on task, particularly with lengthy or repetitive activities.
Difficulty getting ready for school on time.
Appearing as though they are “daydreaming” or not listening when spoken to directly.
In Adolescence
In adolescence, inattentive symptoms manifest as greater academic and social difficulties. This is compounded by parents often providing less guidance and assistance to adolescents, believing that they can now accept more responsibility for tasks such as making their own lunch, remembering what to pack in their bag, and needing less supervision for homework (a number of my ADHD clients have told me they stopped eating lunch when it became their responsibility to make their own). Common challenges include:
Struggling to plan and complete long-term projects or homework.
Forgetting to bring necessary materials to class.
Difficulty managing schedules, leading to missed deadlines or events.
Continued reliance on others (e.g., parents or teachers) for organisation.
See my related blog post on the difficulties some adolescents with ADHD have transitioning to adulthood
In Adulthood
As adults, inattentive symptoms often present in ways that can seriously impact on study, work and relationships:
Chronic procrastination or an inability to meet deadlines at work.
Misplacing important items like keys, wallets, or work documents.
Becoming easily distracted in meetings, conversations, or while performing non-preferred tasks.
Feeling overwhelmed by the demands of daily life, such as managing finances, remembering appointments, or juggling responsibilities.
The Diagnostic Gap: The DSM-5 criteria for inattention focus heavily on academic performance and externally observable behaviours. In adults, these symptoms often appear as internal struggles with memory, planning, and prioritisation, which can go unnoticed without detailed self-reporting.
Hyperactivity: From Boundless Energy to Restless Tension
In Childhood
Hyperactive behaviours are most visible in young children, often drawing attention in structured environments like school. Typical behaviours include:
Fidgeting, squirming, or tapping hands and feet.
Running or climbing in inappropriate settings.
Difficulty sitting still during meals or lessons.
Talking excessively.
In Adolescence
As children grow, hyperactive behaviours often become less overt but may still cause difficulties. Common presentations include:
Persistent restlessness, such as frequently getting up from a desk.
Difficulty engaging in quiet activities, like reading or studying.
Feeling driven by an “inner motor,” leading to a need to stay constantly busy.
Talking to peers in class, sometimes leading to punishment or separation from friends.
In Adulthood
While there are some adults who retain a high need for physical movement, hyperactivity in adults presents more frequently as internalised restlessness:
Feeling unable to relax, even during leisure time.
Speaking quickly or jumping between topics in conversations.
Overworking or overcommitting to projects.
Tapping feet, pacing, or fidgeting.
The Diagnostic Gap: The DSM-5 hyperactivity criteria emphasise observable physical activity, which diminishes with age. Adults often describe their hyperactivity as a "busy mind", an internal feeling of restlessness, or the inability to “switch off” or relax, a nuance that the DSM-5 does not fully capture.
Impulsivity: Immediate Reactions with Long-Term Consequences
In Childhood
Impulsivity in children can be disruptive and socially challenging. Key behaviours include:
Interrupting others or blurting out answers before questions are finished.
Difficulty waiting their turn in games or group activities.
Acting without considering potential consequences, such as running into the street or grabbing toys from others.
Being quick to anger or lash out physically.
In Adolescence
As adolescents develop more independence, impulsivity may lead to riskier behaviours:
Difficulty resisting peer pressure, potentially leading to substance use or risky decisions.
Making decisions without fully considering consequences, such as skipping class or impulsively quitting jobs.
Emotional impulsivity, such as sudden outbursts of anger or frustration.
Unsafe driving and sexual behaviour.
In Adulthood
In adults, impulsivity often results in behaviours with significant personal or financial repercussions:
Impulsive spending, leading to financial difficulties.
Risky behaviours, such as gambling, drug use, or promiscuity.
Difficulty delaying gratification, resulting in trouble saving money or overindulging in food or other pleasures.
Speaking or acting without thinking (oversharing), which may strain relationships or cause workplace conflicts.
The Diagnostic Gap: The DSM-5 criteria for impulsivity are rooted mostly in verbal behaviours (e.g., blurting out answers or interrupting others). However, impulsivity in adults often manifests in ways with more serious consequences, such as financial mismanagement or high-risk activities, which are not explicitly addressed in the current diagnostic framework. Emotional impulsivity is listed as an associated symptom, rather than as part of the core symptom set.
See my related blog post on why emotional dysregulation should be an official symptom of ADHD
The Need for an Evolved Diagnostic Framework
The DSM-5 criteria were initially explicitly constructed with boy children in mind, at a time when ADHD was not seen as continuing into adulthood, or occurring frequently in girls. While some symptoms were adapted for adults in 2013, significant gaps remain. These gaps can lead to underdiagnosis or misdiagnosis in adults, especially when symptoms do not fit the traditional childhood-based descriptions.
In a study published in 2006 designed to inform changes to adult ADHD criteria for DSM-5, Dr. Russell Barkley and Dr. Kevin Murphy examined the applicability of existing ADHD diagnostic criteria to adults. Their research included 146 participants with ADHD and extensive clinical data to a community control group of 109, and a clinical control of 97 who did not have ADHD, and studied the prevalence of the 18 ADHD symptoms and which differed between groups most consistently. The study led to the proposal of nine symptoms for diagnosing ADHD in adults, notably excluding any hyperactivity symptoms. This exclusion reflected the observation that hyperactive behaviours often diminished with age, while issues such as impulsivity and inattention persisted. While this was only a small study, it provides some evidence that a more appropriate evidence-based symptom list could be devised for adults.
Conclusion
ADHD is not a static condition; it transforms across the lifespan, influenced by developmental stages and life demands. By understanding how inattentiveness, hyperactivity, and impulsivity evolve from childhood through adulthood—and acknowledging the limitations of current diagnostic frameworks—we can improve the identification, support, and treatment of ADHD for people at every stage of life.
See my related blog post about how feminising sex hormones can affect ADHD symptoms and mental health across the lifespan
See my related blog post about developmental delays in children, adolescents, and adults with ADHD
This ADDitude article notes changes that occur in boys and girls with ADHD at puberty
Comments