ASD is often accompanied by additional diagnosis. Some of these may include:
Attention deficit hyperactivity disorder (ADHD) is a medical condition where children act before they think, have trouble focusing and can’t sit still a lot of the time. Many children have trouble with some of these things. But in children with ADHD, this behaviour is extreme and has a big impact on children’s daily life.
With ADHD, the different parts of the brain don’t ‘talk’ to each other in a typical way. Because of this, children might have trouble thinking, learning, expressing their feelings or controlling their behaviour as well as other children of the same age. There are three types of ADHD:
- ADHD inattentive type: children with this type tend to have trouble concentrating, remembering instructions, paying attention and finishing tasks.
- ADHD hyperactive/impulsive type: children with this type are always on the go, have trouble slowing down and can often act without thinking.
- ADHD combined type: children with this type tend to have trouble concentrating, are fidgety or restless and are always on the go. They often act without thinking .
People with generalized anxiety disorder (GAD) experience constant, chronic, and unsubstantiated worry, often about health, family, money, or work. This worrying goes on every day, possibly all day. It disrupts social activities and interferes with work, school, or family. Physical symptoms of GAD include the following:
- muscle tension
- difficulty sleeping
- edginess 
Dysgraphia is the condition of impaired letter writing by hand, that is, disabled handwriting. Impaired handwriting can interfere with learning to spell words in writing and speed of writing text. Children with dysgraphia may have only impaired handwriting, only impaired spelling (without reading problems), or both impaired handwriting and impaired spelling .
Dyslexia is a specific learning disability that is neurobiological in origin. It is characterized by difficulties with accurate and/or fluent word recognition and by poor spelling and decoding abilities. These difficulties typically result from a deficit in the phonological component of language that is often unexpected in relation to other cognitive abilities and the provision of effective classroom instruction. Secondary consequences may include problems in reading comprehension and reduced reading experience that can impede growth of vocabulary and background knowledge .
Dyspraxia, a form of developmental coordination disorder (DCD) is a common disorder affecting fine and/or gross motor coordination in children and adults. It may also affect speech. DCD is a lifelong condition. DCD is distinct from other motor disorders such as cerebral palsy and stroke, and occurs across the range of intellectual abilities. Individuals may vary in how their difficulties present: these may change over time depending on environmental demands and life experiences. 
Global Developmental Delay
Global delay can be defined as significant delay in two or more developmental domains: gross and fine motor; speech and language; cognition; personal and social development; or activities of daily living.
Intellectual disability involves impairments of general mental abilities that impact adaptive functioning in three domains, or areas. These domains determine how well an individual copes with everyday tasks:
- The conceptual domain includes skills in language, reading, writing, math, reasoning, knowledge, and memory.
- The social domain refers to empathy, social judgment, interpersonal communication skills, the ability to make and retain friendships, and similar capacities.
- The practical domain centers on self-management in areas such as personal care, job responsibilities, money management, recreation, and organizing school and work tasks.
While intellectual disability does not have a specific age requirement, an individual’s symptoms must begin during the developmental period and are diagnosed based on the severity of deficits in adaptive functioning. The disorder is considered chronic and often co-occurs with other mental conditions like depression, attention-deficit/hyperactivity disorder, and autism spectrum disorder. 
Irlen Syndrome (also referred to at times as Meares-Irlen Syndrome, Scotopic Sensitivity Syndrome, and Visual Stress) is a perceptual processing disorder. It is not an optical problem. It is a problem with the brain’s ability to process visual information. This problem tends to run in families and is not currently identified by other standardized educational or medical tests.
A learning disability is a serious and ongoing difficulty with one or more of the following areas of learning – reading, spelling, writing and maths. A child with a learning disability will have a low level of ability in these areas given the child’s educational opportunities, age and other abilities. These factors must be assessed by a professional.
Oppositional Defiance Disorder (ODD)
To be diagnosed with ODD, a child must show a pattern of angry and cranky moods, along with negative, defiant behaviour that upsets other people. A child must have at least four symptoms from the following list. The child:
- loses his temper
- argues with adults
- actively defies or refuses to obey adults’ requests or rules
- often deliberately annoys people
- often blames others for mistakes or challenging behaviour
- is easily annoyed by others
- is often nasty or unkind.
A child with ODD shows the symptoms often, in a way that interferes with usual daily activities, and for at least six months.
Pervasive Developmental Disorder
The diagnostic category of pervasive developmental disorders (PDD) refers to a group of disorders characterized by delays in the development of socialization and communication skills. Parents may note symptoms as early as infancy, although the typical age of onset is before 3 years of age. Symptoms may include problems with using and understanding language; difficulty relating to people, objects, and events; unusual play with toys and other objects; difficulty with changes in routine or familiar surroundings, and repetitive body movements or behavior patterns.
Rett syndrome is a neurodevelopmenal disorder that affects girls almost exclusively. It is characterized by normal early growth and development followed by a slowing of development, loss of purposeful use of the hands, distinctive hand movements, slowed brain and head growth, problems with walking, seizures, and intellectual disability. 
Sensory Processing Disorder
Sensory Processing Disorder is a condition that exists when sensory signals don’t get organized into appropriate responses. A person with SPD finds it difficult to process and act upon information received through the senses, which creates challenges in performing countless everyday tasks. Motor clumsiness, behavioral problems, anxiety, depression, school failure, and other impacts may result if the disorder is not treated effectively.