ADHD is a common neurodevelopmental disorder emerging in childhood or early adolescence, characterised by a pervasive pattern of developmentally inappropriate levels of inattention and/or hyperactivity- impulsivity that leads to clinically significant functional and psychosocial impairments. The disorder affects around 5% of children, with wide variations between different countries. Longitudinal follow-up studies of children with ADHD show that symptoms of ADHD commonly persist into adulthood, with around two-thirds of cases meeting either full or sub-threshold criteria in adulthood. The prevalence of adult ADHD in epidemiological surveys, assessed with standardized instruments, is estimated at around 2.5–4% of the general population. Although ADHD is recognised as a predominantly male disorder in childhood (clinic-referred children are more likely to be male), in adult samples the gender difference is less pronounced.
Apart from the main symptoms used to classify ADHD, emotional dysregulation is considered to be an associated feature supporting the diagnosis of ADHD. In ADHD, emotional dysregulation is characterised by problems with temper control (feelings of irritability and frequent outburst of short duration), emotional over-reactivity (diminished ability to handle typical life stresses, resulting in frequent feelings of being hassled and overwhelmed), and mood lability (short and unpredictable shifts from normal mood to depression or mild excitement). According to the Diagnostic and Statistical Manual of Mental Disorders (DSM–5), the diagnosis of ADHD requires six out of nine ADHD symptoms of either inattention or hyperactivity/impulsivity in childhood, and five out of nine in adults. Additional criteria include childhood age of onset defined as several ADHD symptoms present before the age of 12 years, pervasiveness defined as symptoms present in two or more settings, and impairment defined as- interference with or reduced quality of social, academic or occupational functioning.
The symptom profile and severity of ADHD varies greatly between individuals, with both inattention and hyperactivity/impulsivity associated with functional impairment in multiple domains. Emotional dysregulation has also been found to be an independent predictor of impairment in ADHD, after controlling for the confounding effects of core ADHD symptoms (inattention and hyperactivity/impulsivity) on impairment. Furthermore, this has been found in cases of ADHD with no co-existing mental health disorders, and therefore cannot be explained by co-occurring conditions. Impairments can be severe, impacting on education, occupation, social and interpersonal relationships. Adults with ADHD are more likely to have lower educational attainment, poorer work performance and an increased likelihood of dismissal from work, as well as difficulties in maintaining long-term social relationships and higher divorce rates, serious transport accidents and criminality. ADHD seldom exists in isolation and up to 90% of adults with ADHD are reported to have one or more cooccurring mental health disorders. Of these disorders, the most prevalent include mood, anxiety and substance use disorders, and personality disorders including BPD.