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Neuroscience of ADHD: Causes, Types, Diagnosis, and Treatment

by Sian Martis, St. Xavier's College (Autonomous), Mumbai, Maharashtra, India


Do you find it difficult to pay attention to the job assigned to you? Do you feel hyperactive at home or in a social setting? Or feel you are constantly restless and fidgeting with everything around them? Do you daydream a lot and end up not listening to the person talking to you? These are completely normal things that we tend to do sometimes, but if it hampers your day to day life-disrupting your social and professional ethics, you might need to check for ADHD. ADHD also is known as Attention Deficit Hyperactivity Disorder is a neurodevelopmental disorder that is not only diagnosed in young children but also adults. Alone in the US, 6.4 million children live with ADHD of ages 4-17 years. It is more likely to be seen in boys than in girls.


Brain scans using fMRI have shown that people with ADHD have differences in the development of brain and brain activity when compared to their peers. The most common cause of ADHD is genetics. Research shows that children who have parents with ADHD have 1 in 4 chances of having it themselves. Other causes of ADHD would be premature birth or low weight at birth, injury to the brain, smoking, drinking, or chronic stress during pregnancy also in some cases exposure to the environment has high toxicity levels. Due to misinformation, it is falsely believed that having a high sugar diet, food additives, immunization along with other assumptions cause ADHD.

ADHD is also known to be caused due to the imbalance of neurotransmitters norepinephrine and dopamine. Dopamine is famously known as the reward system of the brain. It affects the prefrontal cortex, limbic system, basal ganglia, and reticular activating system. The prefrontal cortex is located in the frontal lobe. Its main role is an executive function. It also helps in higher cognitive function, social behavior, decision making, personality development, attention, prioritizing, planning, and organization. The inadequacy of norepinephrine causes malfunctioning of this executive area, inattention, and trouble organizing. Emotion, memory, and homeostatic center of the brain is the limbic system. It consists of the hypothalamus, hippocampus, amygdala and is located on either side of the thalamus. The deficiency in this area can cause inattention, easily distracted from a task, and don’t retain information. Basal ganglia are a group of nuclei present in the midbrain and Diencephalon that helps in cognition as these nuclei are interconnected with one another. Researchers have shown in the basal ganglia the caudate and putamen regions are smaller for people with ADHD. It is known to control emotion, voluntary movement including the inhibition of unnecessary movements, hence basal ganglia can be responsible for the impulsivity generated during ADHD. The main role of the Reticular activating system (RAS) in consciousness, awakeness, arousal, and also in motivation. It helps in the elimination of unnecessary information in the brain. It is a part of the reticular formation in the brainstem and originates close to the spinal cord. The deficiency of the hormone in the RAS can cause inattention and hyperactivity. These areas of the brain are interconnected, therefore causes a cumulative effect on the normal cognition of the brain.


ADHD can be classified into three types-predominantly inattentive types, predominantly hyperactive-impulsive type, and the combined type. The predominantly inattentive type where the person has problems concentrating, get easily distracted, and cannot remember things correctly. The person usually is quiet and doesn't display hyperactivity or impulsivity, hence it is difficult to identify this type. Along with inattention, they tend to have poor organizational skills, lose items needed for the task to be done, daydream a lot, and overall do poorly in school or at work as they cannot follow instructions or don’t listen in general. It is commonly seen in adults and young girls.

In predominantly hyperactive-impulsive, the person is constantly fidgeting, squirmy, find it difficult to be seated, have disruptive tendencies, no self-control as they tend to touch random objects, interrupt while someone is talking or make rude/inappropriate comments, lash out and show extreme mood swings and altogether are very impatient. They are very impulsive and hyperactive and end up indulging in risky behavior. This type of ADHD is mostly seen in men and young boys.

The last one is the combination of both the disorders known as the combination type. In this, the person shows symptoms of both Inattentive and Hyperactive-impulsive categories. When a person exhibits six or more than six symptoms of each type, they tend to have a combination type of ADHD.


The awareness and diagnosis of this disorder have contributed to a large number of cases per year. ADHD is normally diagnosed with other disorders such as Tourette’s Syndrome, anxiety, depression, OCD, oppositional defiant disorder, conduct disorder, various learning disorders, bipolar disorders, etc. That is why it is even more difficult to identify ADHD along with these disorders as they have similar symptoms.

To diagnose a child of ages 4-17 with ADHD, the child should show six or more symptoms of one of the types. They should have the symptoms for more than 6 months. A pediatrician assesses the child by talking to the parents and teachers involved in home and school. Two or more social settings are considered in the assessment. The pediatrician will run neurological and other tests to determine if the child has some other disorders. He/ she will recommend a specialist or child psychiatrist or mental health professional for further treatment. They give the parents and teachers a questionnaire with a rating scale with various questions regarding the behavior, social patterns, learning ability, progress, etc. Based on the frequency, a result is generated which shows the type of ADHD. Considering all this, a holistic approach is generated for the child. Behavioral therapy helps in positive reinforcement in the behavior and social cues of the child. Medication depending upon the child's symptoms are prescribed. Though parents aren’t very comfortable giving their child stimulants at such young ages. Educational interventions and other plans can help a child with ADHD to learn better. ADHD is also known to continue through adulthood.

In adults, diagnosing ADHD is a little difficult. Diagnostic and Statistical Manual of Mental Disorders- Fifth Edition (DSM-5) provides detailed checklists, rating scale that helps determine the type of ADHD. An adult needs to show at least 5 or more symptoms of a type. The behavior of the adult in social groups, work progress, building relationships, impulsive or risky behavior is all analyzed by the diagnostician or the mental health professional. They also try to look at school records and examine their childhood situations. After the diagnosis, medication in the form of stimulants like Adderall, Ritalin, and non-stimulants and therapy is given as a treatment option.

ADHD may be serious if it goes undetected in a person. Celebrities like Justin Timberlake, Paris Hilton, Howie Mandel, Michael Phelps have ADHD and have managed to possess very successful careers. There are many inspirational TED talks on how people with ADHD with the help of different treatments have turned this disorder into a superpower. With the help of therapy, medication, a healthy diet, and proper sleep cycles, a person with ADHD can better their life.


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Image 1: Brain scans

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Image 2: Children with ADHD and other mental disorders

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