The symptoms of attention deficit hyperactivity disorder (ADHD) can be categorised into two broad groups of behavioural problems - symptoms of inattentiveness, and symptoms of hyperactivity and impulsiveness. It is not fully understood whether these problems are an extreme form of normal behaviour, or part of a separate range of behaviour altogether.

People with ADHD usually have symptoms that define them as having one of three subtypes of the condition. The subtypes are:

• ADHD mainly inattentive,
• ADHD mainly hyperactive-impulsive, or
• ADHD combined.

For example, if you or your child has symptoms of all three behavioural problems - inattentiveness, hyperactivity and impulsiveness - they may have ADHD combined, which is the most common subtype of ADHD. Alternatively, if you or your child has symptoms of inattentiveness, but not hyperactivity, or impulsiveness, they may have ADHD mainly inattentive. This form of ADHD is also known as attention deficit disorder (ADD).

Childhood ADHD is more commonly diagnosed in boys than in girls, but this may be due to a tendency for the diagnosis to look for disruptive behaviour, which is more noticeable and tends to be more common in boys than girls. Girls with ADHD often have the mainly inattentive form of the condition, which may make them quiet and dreamy, and can sometimes go unnoticed. As a result, some research suggests that ADHD could be under-diagnosed in girls, and could be more common than previously thought.

Symptoms of ADHD in children and adolescents

The symptoms of ADHD in children and adolescents are well defined. The main symptoms of each behavioural problem are detailed below.

Inattentiveness

• a very short attention span,
• being very easily distracted,
• being unable to stick at tasks that are tedious, or time consuming,
• being unable to listen to, or carry out, instructions,
• being unable to concentrate, and
• constantly changing activity, or task.

Hyperactivity

• being unable to sit still, especially in calm or quiet surroundings,
• constantly fidgeting,
• being unable to settle to tasks, and
• excessive physical movement.

Impulsiveness

• being unable to wait for a turn,
• acting without thinking,
• breaking any set rules, and
• little or no sense of danger.

If your child has ADHD, their symptoms usually become noticeable at around the age of five. ADHD can cause many problems in your child's life, and can often lead to underachievement at school, poor social interaction with other children and adults, and problems with discipline.

Although it is not always the case, your child may also have other problems, or conditions alongside ADHD. These are detailed below.

Anxiety disorder

Some children with ADHD may have an anxiety disorder which causes them to worry and to be nervous much of the time. Your child may also have physical symptoms, such as a rapid heartbeat, sweating and dizziness.

Oppositional defiant disorder (ODD)

Oppositional defiant disorder (ODD) is defined by negative and disruptive behaviour, particularly towards authority figures, such as parents and teachers. It is common among children with ADHD.

Conduct disorder

Children who have conduct disorder have a tendency towards highly antisocial behaviour, such as stealing, fighting, vandalism, and harming people and animals. If your child is behaving in this way, you should seek professional help as soon as possible.

Depression

It is possible for children who have ADHD to become depressed as a result of their condition.

Sleep problems

Children with ADHD, who are very hyperactive, may find it difficult to settle to sleep at night, and may experience irregular sleeping patterns.

Epilepsy

Epilepsy is a condition of the brain which causes seizures.

Tourette's syndrome

Tourette's syndrome is a condition of the central nervous system that causes involuntary movements and sounds.

Learning difficulties, such as dyslexia

It is thought that up to 35% of children with ADHD also have learning difficulties. However, it is important to remember that ADHD has no effect on intelligence.

Symptoms of ADHD in adults

In adults, the symptoms of ADHD are more difficult to define than those in children and adolescents, which is largely due to a lack of research into the adult form of the condition.

It is still uncertain whether or not ADHD can occur in adults without it first appearing during childhood, although it is known that symptoms of ADHD often persist from childhood into adolescence and adulthood. Any additional problems, or conditions, experienced by children with ADHD, such as depression, sleep problems and dyslexia, are also likely to carry on into adulthood.

By the age of 25, an estimated 15% of people diagnosed with childhood ADHD still have a full range of symptoms, and an estimated 65% still have symptoms which affect their daily lives.

There is no definitive list of adult ADHD symptoms, and experts agree that simply applying the childhood symptoms to adults would not work. This is because the way in which inattentiveness, hyperactivity, and impulsiveness affect adults, is very different from the way they affect children. For example, hyperactivity tends to decrease in adults, while inattentiveness tends to get worse as the pressure of adult life increases. Also, adult symptoms of ADHD tend to be far more subtle than childhood symptoms.

Below is a list of symptoms which may be used to recognise adult ADHD.

• carelessness and lack of attention to detail.
• continually starting new tasks before finishing old ones.
• poor organisational skills.
• inability to focus, or prioritise.
• continually losing, or misplacing, things.
• forgetfulness.
• restlessness and edginess.
• difficulty keeping quiet, and speaking out of turn.
• blurting responses, and poor social timing when talking to others.
• often interrupting others.
• mood swings.
• irritability and a quick temper.
• inability to deal with stress.
• extreme impatience.
• taking risks in activities, often with little, or no, regard for personal safety, or the safety of others.

As with ADHD in children and adolescents, ADHD in adults can appear alongside many related problems, or conditions. One of the most common conditions is depression. Any problems you may have had as a child are likely to persist into adulthood, which can make life extremely difficult. For example, you may have problems finding and keeping employment, as well as relationship, and social interaction problems. Some adults with ADHD may even become involved in drugs, or crime.