Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterized by a persistent pattern of inattention and/or hyperactivity-impulsivity that interferes with daily functioning or development. It usually begins in childhood and can persist into adolescence and adulthood. Prevalence estimates vary depending on the diagnostic method used, but they are around 5-7% of the child and adolescent population.
It is a heterogeneous condition: not all people with ADHD present the same profile, nor with the same intensity, nor in the same contexts. That is why current research and guidelines insist on understanding it as a condition of multifactorial origin, with different clinical expressions and developmental trajectories.
A multifactorial model: genetics, neurobiology, and environment
Due to its complexity, ADHD cannot be attributed to a single cause. The available evidence points to the interaction between genetic, neurobiological, and environmental factors that, when combined, increase the likelihood of developing the disorder.
Genetics and heritability. Family and twin studies show high heritability, consistently around 70-80%. This does not imply determinism in each person, but rather that an important part of the variability observed in the population is influenced by genetic factors.
Polygenic architecture. In most cases, genetic risk is polygenic: many common variants are involved, each with a small effect. Large genomic studies have identified dozens of risk loci and have linked ADHD to genes involved in early brain development and in cognitive functions such as attention and executive functions.
Environmental factors. Environmental factors rarely act as a “single cause,” but they can be associated with increased risk. Among the most studied are prenatal exposure to tobacco or alcohol, lead exposure, prematurity or low birth weight, some prenatal or perinatal complications, and traumatic brain injuries in childhood. It is important to understand them as risk factors, not as deterministic explanations in each case.
Symptoms and manifestations
ADHD is expressed through symptoms of inattention and/or hyperactivity-impulsivity. Currently, people speak of clinical presentations—predominantly inattentive, predominantly hyperactive-impulsive, or combined presentation—because the way it manifests can change throughout development.
Inattention
Inattention involves difficulties sustaining attention, selecting what is relevant, organizing information, and maintaining mental effort when the task requires it.
- Lack of attention to detail and careless mistakes.
- Difficulty maintaining attention in tasks or activities.
- Appears not to listen when spoken to directly.
- Does not follow instructions or does not complete tasks.
- Difficulties organizing activities and managing time.
- Avoids tasks that require sustained mental effort.
- Loses objects needed for daily life.
- Is easily distracted by external or internal stimuli.
- Forgets everyday activities.
Hyperactivity
In childhood, it is observed as excessive movement; in adults, it may be expressed more as inner restlessness or difficulty remaining still.
- Fidgets in the seat or moves hands and feet excessively.
- Gets up in situations where they should remain seated.
- Runs or moves excessively in inappropriate situations.
- Difficulty playing or relaxing quietly.
- Feeling of being constantly on the go.
- Talks excessively.
Impulsivity
Impulsivity reflects difficulties inhibiting responses, waiting, or considering consequences before acting.
- Answers before the question is finished.
- Difficulty waiting for their turn.
- Interrupts other people’s conversations or activities.
- Makes hasty decisions or takes risks.
Beyond the core symptoms
Many people with ADHD also present difficulties in executive functions, such as planning, organization, time management, or task completion. These difficulties explain a large part of the disorder’s impact on daily life.
Clinical presentations of ADHD
People speak of presentations because the profile can change with age and context.
Combined Presentation (ADHD-C)
It constitutes the most prevalent phenotype, accounting for between 50% and 75% of cases. In this group, both attention deficit and hyperactivity-impulsivity exceed the clinical threshold and are functionally equivalent in their disruptive impact.
Predominantly Inattentive Presentation (ADHD-PI)
It represents approximately 15% of diagnoses, with the predominant symptom being profound inattention, with an absence of clinical levels of overt hyperactivity. These users, who seem to be constantly daydreaming or lost in thought, often go unnoticed in the classroom because they do not display disruptive behavioral problems.
Predominantly Hyperactive/Impulsive Presentation (ADHD-HI)
It characterizes about 20% of diagnosed adults. In this subtype, agitation, chronic inner restlessness, and instinctive reactivity predominate, operating with an attentional deficit that, although present, does not reach the severity of the motor and impulsivity dimensions.
Diagnosis and assessment
Diagnosis requires a complete clinical assessment. There is no single diagnostic test.
- Onset of symptoms before age 12.
- Persistence for at least 6 months.
- Presence in two or more contexts (home, school, work).
- Significant impairment in functioning.
- Not better explained by another disorder.
Comorbidity and impact
Coexistence with other disorders such as anxiety, depression, learning difficulties, or behavioral problems is common. This can increase the impact on academic performance, social relationships, and daily life.
Intervention and treatment
Treatment for ADHD is usually multimodal and individualized.
- Psychoeducation for the user and family.
- Behavioral intervention and parent training.
- Educational supports and accommodations.
- Pharmacological treatment when indicated.
- Psychological intervention focused on executive functions and self-regulation.
An appropriate approach makes it possible to reduce symptoms and significantly improve quality of life.
