Neurodevelopmental disorders are characterized by delays or difficulties in the acquisition of motor, social, language or cognition skills. Developmental disorders are extremely diverse. Some children will be minimally affected, while others will need lifelong assistance.
Cognitive functioning is significantly below that expected for the child's age, and leads to failure to meet developmental skills for independent living. The child has deficits in functions such as problem-solving, planning, reasoning, academic learning, and learning from experience.
ADHD make affect up to 7% of children and 4% of adults. It is characterized by difficulty focusing and/or hyperactivity and impulsivity.
ASD is characterized by difficulty with social interactions, repetitive behaviors, and/or obsessive interests.
Clinical diagnosis is based on assessment of cognitive and developmental functioning using standardized measures. It is a "functional diagnosis," not a causal (etiologic) diagnosis.
Further compounding the situation, many developmental disorders co-occur, such as autism spectrum disorder and intellectual development disorder. Last but not least, cognitive and communication deficits may result in inappropriate behavior and "acting out," which may be mistaken for a behavioral disorder.
Neuropsychological testing is an essential part of differentiating among various developmental disorders.