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Column originally published Mar 27, 2007

Aggressive Behaviour Can Be A Symptom Of Oppositional Defiant Disorder

Question: We are very concerned about our seven-year-old son. For the last three years, he has become more and more aggressive. He was kicked out of one kindergarten because of hitting and choking other children, and he showed no remorse. Most of the time there is nothing that seems to trigger his aggression. When he watches a hockey game, he is fascinated by the fighting instead of the game. A few weeks ago, when he got angry, he picked up a piece of rock and smashed the headlight out of his father’s tractor. None of our family is like that, and he was never exposed to any kind of violence. Our ten-year-old son was recently diagnosed to have Attention Deficit Hyperactivity Disorder, but he is nothing like his younger brother. We are wondering whether there is any relationship between our younger son’s aggression and his older brother’s hyperactivity, and how to manage his behaviour.


The severe aggressive behaviour that you have described falls under a group of psychiatric conditions called Disruptive Behaviour Disorders.  Included in this group of disorders are Attention Deficit Hyperactivity Disorder (ADHD), Oppositional Defiant Disorder (ODD), and Conduct Disorder (CD).  These are very complex medical conditions that I will try to describe here so that you can have a better understanding of your son’s problem, and get proper help for him.

ADHD is a medical condition that affects children and adults.  Some of them are physically hyperactive and impulsive, although many only have difficulty paying attention to academic work or things that they are not particularly interested in.  Temper tantrum is not uncommon, but it tends to improve when the child gets older.

Children with ODD are often stubborn, argumentative, and have difficulty following rules.  They can get angry very easily, and they seem to antagonize others on purpose.  Very often, they blame others for their mistakes.  These children have more frequent and more severe temper outbursts than their peers.

Most children with ODD are diagnosed between 6 to 10 years of age, although many continue to have problems well into teenage years.  In some, their symptoms gradually improve over time, although a significant proportion will get worse and show signs of conduct disorder when they get older.

Conduct disorder is a much more serious medical condition.  It can occur in children under 10 years of age, but can also begin in teenagers who have no behaviour issue earlier.  Many are extremely physically aggressive, especially towards their family members and other students in school.  They often bully, threaten, or intimidate others, as well as initiating physical fights.  They get angry very easily, and they frequently hold a grudge.  They can hurt and kill animals with no remorse.  Many are involved in assaults and robbery.  In short, their behaviour is well beyond what is normal for children and teenagers, and many of their activities are against the law.

In addition to these aggressive behaviour, many are involved in vandalism, theft, cheating, skipping school, breaking curfews, and other rules set out by parents, school, and other authorities.

Many are also involved in sexual activity early, including sexual assault and coercion of others to have sex.  Girls with CD may not be as physically aggressive as boys, but they are capable of verbal abuse and bully, as well as other illegal activities.  They are also prone to running away from home and becoming involved in prostitution.  They are just as likely as boys to abuse drugs and alcohol.

Just like any other medical condition, children and adolescents can have mild to severe CD.  Those with mild problems have a good chance of learning socially appropriate behaviour and grow up as normal adults.  However, 30% to 50% of youths with childhood-onset CD will be diagnosed with anti-social personality disorder and involved in criminal activities as adults.  They are also prone to other psychiatric disorders, including anxiety and mood disorders.

What causes ODD and CD is still unknown.  Research has shown that genetic factors and environmental influence are both important in the development and progression of ODD and CD.  Several brain chemicals (including dopamine, nor-adrenaline, and serotonin) don’t work properly in many of these children.

Not all children who have the genetic tendency will develop ODD and CD.  Having a good relationship with the parents, attending school with supportive teachers, and maintaining friendship with peers who have normal social behaviour can prevent the development of ODD and CD.  An intelligent teenager who is successful academically and socially, and is involved in healthy after-school activities, are less likely to develop progressive behaviour problems.

However, if the family is involved in illegal or criminal activities, these children will be more likely to adopt similar behaviour.  Teenagers who suddenly develop aggression should be screened for drug abuse as well as previously unrecognized mood disorder.  Some teenagers may get involved in criminal activities in order to fit in with their peers.

To complicate things further, some children with ADHD also have symptoms of ODD and CD.  Furthermore, those who have ODD and CD often have symptoms of ADHD.  All these three conditions may be genetically linked in some families.  This may explain why your older son has ADHD, and your younger son has symptoms of ODD and CD.

Having a child with aggressive behaviour like your son challenges the whole family.  Your first step is to consult a child psychiatrist or a paediatrician who is knowledgeable about these medical conditions.  Both of you need to support each other in dealing with your son’s aggression.  You have to pick your battles and work on those issues that are least acceptable; use time-out instead of getting angry at his behaviour; praise him when he behaves properly; engage him in healthy after-school activities; don’t allow him to play violent videogames; and establish reasonable age-appropriate limits with consequences that are enforced consistently by all adults.

Unfortunately, behaviour management alone may not result in adequate control of your son’s aggression.  Many have abnormal brain chemical function that will benefit from medications.  This is especially true if he also has symptoms of ADHD.  Medicine that is effective for ADHD may help a child to control his impulsive reaction and reduce some of the aggressive behaviour.  However, it is far too complex for me to discuss any specific medicine here.

While early-onset aggressive behaviour is very difficult to manage, it is far more difficult to correct if left untreated, because it can lead to more serious psychiatric conditions when he grows up.