TDAH stands for “Trastorno por Déficit de Atención e Hiperactividad,” the Spanish term for what English speakers know as ADHD, or attention deficit hyperactivity disorder. It is a neurodevelopmental condition that affects how the brain regulates attention, impulse control, and activity level. Around 2.6% of adults worldwide live with persistent ADHD, and it is one of the most commonly diagnosed conditions in children. Whether you’ve encountered the term TDAH in another language or are just beginning to learn about ADHD, what follows covers what the condition actually involves, what causes it, and how it’s managed.
The Three Types of ADHD
ADHD is not a single pattern of behavior. It shows up in three recognized forms: predominantly inattentive, predominantly hyperactive/impulsive, and combined.
The inattentive type is what people sometimes still call “ADD.” It shows up most clearly during tasks that require sustained focus, careful listening, or organized thinking. A person with this type might lose track of conversations, miss details in schoolwork, or struggle to follow multi-step instructions. They’re not choosing to tune out. Their brain has difficulty filtering what deserves attention and what doesn’t.
The hyperactive/impulsive type involves excessive physical activity and snap decisions that can lead to trouble. In children, this might look like an inability to sit still in class, blurting out answers, or running into a street without checking for cars. In teens and adults, impulsivity can take the form of quitting a job or a relationship on a whim without thinking through consequences.
The combined type includes significant symptoms of both inattention and hyperactivity/impulsivity. This is the most commonly diagnosed presentation.
What Causes It
ADHD is highly heritable. Across 37 twin studies, the average heritability came out to 74%, meaning genetics account for roughly three-quarters of the risk. If a biological parent has ADHD, their child is significantly more likely to develop it as well. That said, heritability below 100% means environmental factors also play a role, likely through changes in how genes are expressed rather than changes to the genes themselves.
At the brain level, ADHD is linked to weaker function and smaller size in the prefrontal cortex, particularly on the right side. This region acts as the brain’s control center for planning, organizing, staying on task, and stopping yourself from acting on impulse. It depends heavily on two chemical messengers: norepinephrine, which strengthens useful brain connections (boosting the “signal”), and dopamine, which weakens irrelevant ones (reducing the “noise”). In people with ADHD, one or both of these chemicals are often at suboptimal levels. Depleting them in animal studies produces deficits as severe as physically removing the prefrontal cortex altogether.
How It Looks Different in Adults
ADHD does not simply disappear after childhood. Symptoms often persist into adulthood, though they tend to shift. Inattentive symptoms, like difficulty organizing tasks or following through on projects, usually remain stable over time. Hyperactivity, on the other hand, typically becomes less visible. An adult with ADHD is unlikely to be climbing furniture, but they may feel an internal restlessness, a constant need for stimulation, or an inability to sit through a long meeting without fidgeting. They might talk excessively or feel mentally “revved up” even when they look calm on the outside.
For a formal diagnosis, symptoms must have started before age 12, even if the diagnosis itself comes decades later. Many adults are identified only after a child in their family is diagnosed and they recognize the same patterns in their own lives.
Why Girls and Women Are Often Missed
ADHD is diagnosed far more often in males than females, but this gap is partly an artifact of how the condition expresses itself across genders. Girls with ADHD tend to present with the inattentive type rather than the hyperactive/impulsive type. They daydream instead of disrupting class. They internalize their struggles as anxiety and depression rather than acting out with rule-breaking behavior.
This matters because the children most likely to get referred for evaluation are the ones causing visible problems. Teachers refer boys for ADHD assessment more often than girls, even when both show equal levels of impairment. In female patients, other diagnoses like anxiety or depression are frequently made long before anyone considers ADHD. Research has found that the most distinguishing non-ADHD symptom in girls is self-reported physiological anxiety, while in boys it’s parent-reported rule-breaking. Since anxiety is harder for parents and teachers to observe from the outside, it often goes unreported, and the underlying ADHD goes unrecognized. Including self-report measures in clinical evaluations can help close this gap.
Conditions That Commonly Occur Alongside ADHD
About 70% of adults with ADHD also have at least one other mental health condition. Anxiety disorders and depression are among the most common, but the list also includes bipolar disorder, substance use disorders, and personality disorders. In children, oppositional and conduct-related behavior problems frequently overlap with ADHD, particularly in boys.
These co-occurring conditions aren’t just coincidental. The same prefrontal cortex circuits involved in ADHD also regulate emotional responses, so difficulty managing frustration, mood swings, and emotional sensitivity are often part of the package. Treating only one condition while ignoring the others tends to produce incomplete results.
How ADHD Is Treated
Medication
Stimulant medications remain the first-line treatment and are considered among the most effective psychiatric medications available. Methylphenidate (the active ingredient in Ritalin) was first approved for behavioral problems in the 1960s, and stimulants have remained central to ADHD treatment ever since. They work by increasing dopamine and norepinephrine activity in the prefrontal cortex, directly addressing the chemical shortfall at the root of symptoms. Most people notice effects within an hour of taking them.
For people who don’t respond well to stimulants or prefer to avoid them, non-stimulant options exist. Atomoxetine, approved in 2002, increases norepinephrine levels in the brain without the addictive properties of stimulants, which means it isn’t classified as a controlled substance. A second category of non-stimulants, including guanfacine and clonidine, were originally blood pressure medications that were repurposed for ADHD after researchers discovered they help keep prefrontal cortex circuits properly connected.
Therapy
Cognitive behavioral therapy adapted for ADHD takes a different approach than the version used for anxiety or depression. Rather than focusing primarily on emotions, it targets the executive function problems that create real-world impairment: time management, organization, planning, prioritizing, and overcoming procrastination. Sessions teach specific behavioral strategies for scheduling, tracking tasks, and managing distractions, alongside cognitive techniques for recognizing the negative thought patterns (“I’m lazy,” “I can’t do anything right”) that often develop after years of struggling.
UK and Australian clinical guidelines recommend CBT as a first-line intervention for adults with ADHD, either alongside medication or on its own. Research supports its use in both roles. When compared against simple psychoeducation or social support, CBT produces meaningfully larger improvements in core ADHD symptoms, suggesting it offers benefits beyond just having someone to talk to.
Living With ADHD
ADHD is not a character flaw or a lack of willpower. It is a brain-based condition with well-documented structural and chemical differences visible on imaging scans. People with ADHD can focus intensely on things that interest them, which sometimes leads others to assume they could focus on everything “if they just tried harder.” That misunderstanding causes real harm. The difficulty lies in directing and sustaining attention on demand, particularly for tasks that aren’t inherently stimulating.
With appropriate treatment, whether medication, therapy, environmental changes, or some combination, most people with ADHD see significant improvements in their ability to function at work, in school, and in relationships. The key is accurate identification, which for many people, especially women and adults, still comes later than it should.