People with autism may behave in different ways even if they have the same condition.

Autistic spectrum disorders cannot be diagnosed using physiological tests, such as blood tests. However, blood tests and hearing tests may be carried out to rule out other health conditions and difficulties.

Most children are diagnosed with autism between the ages of one and three years old. Parents often start to notice symptoms and signs after the age of 12 months. However, some children may start to display signs much later on and symptoms often become much more visible when children start school.

If you notice symptoms such as a lack of eye contact, no response to verbal cues, no attempt to engage with other children or adults, no apparent reaction to familiar voices and an abnormal reaction to unfamiliar sounds, this may indicate that your child has an autistic spectrum disorder. If you notice any of these symptoms or you have concerns about your child, you should arrange to see your GP.

However there are many signs and characteristics that are common to autistic spectrum disorders; these include:

• Repetitive behaviour: many people with autism carry out specific actions repeatedly, such as clicking their fingers, flapping their hands and rocking backwards and forwards.
• Routine behaviour and resistance to change: autistic people are often insistent on a strict routine and get upset and agitated if the routine is disrupted. People with autism do not usually deal with change very well because they have difficulty understanding what is going on.
• Difficulty with verbal communication: children may use gestures instead of words.
• Being alone: most people with autism prefer to be alone and they may struggle in social situations, and some may get worried and upset when they are in a large crowd.
• Laughing for no apparent reason.
• Disinterest in physical contact and struggling to show and understand affection.
• Obsessive behaviour.
• Affinity with certain objects.
• Tantrums and difficult behaviour.
• Unresponsive to verbal cues: children may appear as if they haven’t heard anything and will look completely blank.
• Difficulty forming friendships and mixing with other people.
• Difficulty understanding abstract concepts: focus on facts and concrete information.
• Lack of awareness of pain.
• Strange play routines: a child may sit and stare at a spinning top for hours, for example but will be completely disinterested in an interactive toy with flashing lights and noises.
• No fear of danger.
• Difficulty understanding humour and emotions
• Difficulty understanding anything that is used in a metaphorical sense: for example, when people say that something is cool, meaning that they like it, rather than meaning it is slightly cold to touch.