It is important to understand the behavioural and emotional effects of the syndrome, as they can be as significant as developmental delays. Because people with fragile X syndrome look much the same as others, their behaviour problems can be misinterpreted.

Almost all people with the syndrome have trouble self-regulating their behaviour. This shows up in problems such as:

• Attention deficit disorders and hyperactivity – which can impair learning
• Repetitive behaviours
• Late toilet training
• Disturbed sleep
• The inability to control emotions
• Lack of control of emotional behaviour can result in tantrums or other emotional outbursts.

Both males and females:

• Find concentration difficult.
• They may be quite severely hyperactive and impulsive.
• They may have fixed interests in objects and
• They can strongly dislike any change in routine.

Some behaviour, most obvious with males, is similar to autism. For instance,

• Children can refuse to be touched or held.
• There can be difficulty with making eye contact.
• Hand flapping is often found, which becomes more vigorous when the person is anxious or excited.
• Some people bite their hands or chew their clothing. This can be a way to calm themselves.

Females with fragile X:

• May be shy and moody
• Lack social skills
• May avoid social contact
• They can suffer from depression and severe anxiety.
• Refusing to talk in certain situations (selective mutism) can be exhibited.

Despite the behavioural challenges outlined, people with fragile X often enjoy being social, have pleasant personalities and a good sense of humour.