Mean Gene

We look at a genetic link to ADHD
By Lisa Lazarus

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For Tamsyn*, the most frustrating thing about Attention Deficit Hyperactivity Disorder (ADHD) is “that feeling of your head never quite switching off.” She should know. Like her 13-year-old son, this stay-at-home Pretoria mother of two children, aged 16 and 13, also has ADHD, though Tamsyn was only diagnosed as an adult. Tamsyn knew from early, probably around the time her son started pre-school, that he suffered from ADHD. “This may sound presumptuous,” she says, “to know so soon, but I grew up in a house with an older sister who was diagnosed with ADHD. My folks didn’t simply put this down to middle-child syndrome or to being difficult or insolent. Instead, from the outset, they found help for her.”
Making the connection
Although she initially believed that the condition had passed her by, Tamsyn realised that this wasn’t the case when she started doing intense therapy with her son. She says: “They asked him, ‘do you count things in your head?’ and I answered ‘Yes’ for myself. After that, I started doing some research.” Looking back on her own childhood, a lot of things make more sense now – for example, the frustration of not being able to finish a task immediately. According to the Attention Deficit and Hyperactivity Support Group of Southern Africa (Adhasa), between eight percent and 10 percent of the South African population have ADHD – a term used to include ADD (Attention Deficit Disorder) as well. The disorder appears to be almost twice as prevalent amongst boys as girls.
Mental health practitioners differentiate between three sub-types of ADHD: predominantly inattentive with little or no sign of impulsivity and hyperactivity; predominantly impulsive and hyperactive with little or no attention difficulties; the combined type – distractible, hyperactive and impulsive.
An “Aha!” moment
In 2010, The Lancet, a medical journal, claimed to have found a genetic link to ADHD. Those with ADHD, they said, had more chromosomal structural abnormalities, specifically more copy-number variants. In other words, on certain chromosomes, genetic material had either been deleted or duplicated. Dr Lynda Albertyn, child psychiatrist and head of the Child, Adolescent and Family Unit at Johannesburg Hospital, adds that even before the growing genetic evidence, which has been reported in the journals for several years now, there was convincing evidence from twin and adoption studies that ADHD is largely inherited.
Nine-year-old Tom* has Attention Deficit Disorder (ADD) and so does his mother Helen, a graphic and fashion designer who lives in Port Elizabeth with her three children. Like her son, Helen would go “into a daze and then wake up in a panic” at school. Frequently, teachers would report that she was not applying herself and was capable of more. “I know what it’s like for Tom with the kind of daily battles he has to face at school,” she says. Yet Helen has made great strides with Tom: she has changed his medication (overly high doses of Ritalin were making him depressed, weepy and paranoid), she moved him to a more nurturing school and found two mentors to motivate him – Richard Branson and reality TV personality Ty Pennington, who also suffer from ADHD.
According to Jessica Cheesman, a recent Masters graduate from the University of Cape Town, studies show that the average heritability of ADHD is 0.75. That means that approximately 75 percent of the cause of this disorder is genetic. During Jessica’s research on how mothers of children with ADHD experience stress, she found that many moms had an “Aha!” moment about their own mental health when their children received their ADHD diagnosis. “Often mothers would express how they saw features of themselves in their children, and this gave them some solace in their child’s diagnosis,” she says.
The argument in The Lancet, however, has come under some fire. The BBC’s online medical correspondent Fergus Walsh says: “There is a danger in reading too much into The Lancet’s new research on attention deficit hyperactivity disorder.” Supposedly, children with ADHD were “twice as likely to have chunks of DNA missing or duplicated.” However, drilling down into the numbers, around 15 percent of the ADHD children actually had the genetic variant – in other words, 85 percent did not, which “hardly justifies confident assertion that ADHD is a genetic disease.” In response, Professor Thapar, the spokesperson for the research, said that the study aimed to remove the stigma associated with ADHD. The condition “could not be dismissed as being down to bad parenting or poor diet.”
Getting a handle on it
Albertyn states that there is promising research on the effects of the environment on genes. “Certain environmental factors such as birth damage or an adverse childhood can act on genetic vulnerabilities, which then lead to the development of a disorder. So, someone with a genetic predisposition for ADHD, who has firm and structured parenting, will manifest fewer symptoms than a child with the same genetic predisposition who is raised in a chaotic household.”
Despite the fact that the cause of ADHD is complex – most probably a subtle blending of genetics and the environment – parents of children who suffer from ADHD may benefit from looking at their own childhood. It’s possible that they will identify with what their children are experiencing. 
*Names have been changed.
Does your child have ADD/ADHD?
Attention Deficit Disorder:
  • Often fails to pay close attention to details or makes careless mistakes.
  • Often has difficulty sustaining attention in tasks or activities.
  • Often does not seem to listen when spoken to directly.
  • Often does not follow through on instructions.
  • Often has difficulty organising tasks and activities.
  • Often avoids tasks that require sustained attention.
  • Often loses things necessary for tasks.
  • Easily distracted by extraneous stimuli.
  • Is forgetful in daily activities.
Attention Deficit Hyperactivity Disorder:
  • Often fidgets with hands or feet or squirms in seat.
  • Often leaves seat in classroom or other situations.
  • Often runs or climbs excessively in situations where it is inappropriate to do so.
  • Often has difficulty playing quietly.
  • Is often “on the go” or often acts as if “driven by a motor”.
  • Often talks excessively.
  • Often blurts out answers before questions have been completed.
  • Often has difficulty waiting their turn.
  • Often interrupts or intrudes on others.
  • Often engages in dangerous activities.
From the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition.


denise oosthuizen wrote 7 years 32 weeks ago

I have ADD. My husband, his brother and their father have ADHD! My son, now 12, was diagnosed at the age of 3. All the latest research shows that there is a strong genetic link. We're one big happy family of ADDers!

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