ADHD Causes and Risk factors

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By Ananya Mandal, MDReviewed by April Cashin-Garbutt, MA (Cantab)

ADHD (short for Attention Deficit Hyperactivity Disorder) encompasses a wide range of behavioural disorders characterized by lack of attention and concentration, hyperactivity and inability to control impulsivity.

Causes of ADHD

A parent of a recently diagnosed child may blame themselves or their parenting, but more often than not the cause of the condition is not related to parenting at all.

Parenting and environment, however, may, to a certain extent, be responsible for worsening the child’s behavioural problems.

Risk factors of ADHD

There are no definite causes that have been found to trigger ADHD in a child. However, the following factors may contribute to a raised risk of the condition:-

Altered anatomy or function of the brain – Brain scans have shown that some areas of the brain especially those related to activity and attention spans are different among children and adults with ADHD. (1) Some studies reveal that the frontal lobe of the brain (lies in the forefront of the brain) is different among people with ADHD. This area is related to decision making. There may also be derangement of neurotransmitters like dopamine and noradrenaline in the brain. These neurotransmitters are chemical messengers of the brain. (2)
Genetics – ADHD sometimes may be inherited. There are studies that have found several genes that are related to ADHD causation. (1)
Being male – Boys and men are more at risk of developing ADHD than girls and women. This could be due to genetic factors or hormonal factors. Studies suggest that since ADHD is commonly associated with violent and hyperactivity symptoms, many girls who have predominant inattentive type of ADHD maybe missed out while diagnosing. These girls often grow up to manifest the condition as adolescents or young adults. (2)
Maternal drug abuse, alcohol intake and smoking – Some studies have shown that pregnant women who smoke, take alcohol or use recreational drugs are at a higher risk of giving birth to children who go on to develop ADHD. The exact pathology behind this association is not well known. However, it is speculated that this type of abuse in utero, or within the womb, reduces the neuronal activity and alters the nerve messenger chemicals neurotransmitters. Pregnant women who are exposed to environmental toxins are also at risk of giving birth to babies who may develop ADHD. (1)
Exposure to toxins – Toddlers and preschoolers who are exposed to environmental poisons and toxins are also at higher risk of behavioural problems. Notable among these is lead exposure from paint and pipes in old buildings that has been linked to short attention spans and violent behaviour in some children. (1)
Traumatic brain injury – Brain injury has also been linked to ADHD in some studies. However the number of children who have suffered such brain injuries is too small to explain the rising prevalence of ADHD. (3)
Additives – Some food additives such as preservatives and artificial colouring have been linked to aggravation and increased risk of ADHD. Detailed research in this area is warranted as there is no definitive evidence. (1)
Sugar – Studies and common belief says excess sugar in a child’s diet often leads to behavioural problems. However, detailed studies have shown that there is no association between excess sugar in diet and raised risk of ADHD or even worsening of symptoms in children diagnosed with ADHD. (3)
Food intolerance – Certain food intolerance like that to milk, wheat and nuts has also been linked to raised risk of ADHD. (2)
Exposure to television – There have been concerns that excessive exposure to television at a young age may lead to an increased risk of ADHD. Although there are no studies that actually prove this association; there is evidence that exposure to excessive television may lead to inattentiveness and risk of ADHD later in life. (2)
Other risk factors – These include being born prematurely before 37 weeks of gestation and being born with a low birth weight. Brain damage in utero, or in the first few years of life, or having impaired hearing is also linked to ADHD (2)