In children with ADHD, insomnia is the most common sleep disorder with behavioral therapy being the preferred treatment. Problems with sleep initiation are common among individuals with ADHD but often they will be deep sleepers and have significant difficulty getting up in the morning. Melatonin is sometimes used in children who have sleep onset insomnia. Specifically, the sleep disorder restless legs syndrome has been found to be more common in those with ADHD and is often due to iron deficiency anemia. However, restless legs can simply be a part of ADHD and requires careful assessment to differentiate between the two disorders. Delayed sleep phase disorder is also a common comorbidity of those with ADHD.There are other psychiatric conditions which are often co-morbid with ADHD, such as substance use disorders. Individuals with ADHD are at increased risk of substance abuse. : 9  This is most commonly seen with alcohol or cannabis. : 9  The reason for this may be an altered reward pathway in the brains of ADHD individuals, self-treatment and increased psychosocial risk factors. : 9  This makes the evaluation and treatment of ADHD more difficult, with serious substance misuse problems usually treated first due to their greater risks. Other psychiatric conditions include reactive attachment disorder, characterised by a severe inability to appropriately relate socially, and sluggish cognitive tempo, a cluster of symptoms that potentially comprises another attention disorder and may occur in 30–50% of ADHD cases, regardless of the subtype.
Otherwise, the disorder was classified as disturbance of activity and attention, other hyperkinetic disorders or hyperkinetic disorders, unspecified. The latter was sometimes referred to as hyperkinetic syndrome. Social construct theory
The social construct theory of ADHD suggests that, because the boundaries between normal and abnormal behavior are socially constructed (i.e. jointly created and validated by all members of society, and in particular by physicians, parents, teachers, and others), it then follows that subjective valuations and judgements determine which diagnostic criteria are used and thus, the number of people affected. This difference means using DSM-IV criteria could diagnose ADHD at rates three to four times higher than ICD-10 criteria. Thomas Szasz, a supporter of this theory, has argued that ADHD was "invented and then given a name". Adults
Adults with ADHD are diagnosed under the same criteria, including that their signs must have been present by the age of six to twelve. The individual is the best source for information in diagnosis, however others may provide useful information about the individuals symptoms currently and in childhood; a family history of ADHD also adds weight to a diagnosis. : 7, 9  While the core symptoms of ADHD are similar in children and adults, they often present differently in adults than in children: for example, excessive physical activity seen in children may present as feelings of restlessness and constant mental activity in adults.