This review was funded by Janssen, Purdue and Shire, now part of Takeda
Adult ADHD is frequently associated with comorbid psychiatric disorders, which can complicate its recognition, diagnosis and management. This review aimed to:
- Determine the prevalence, burden and neurobiology of adult ADHD based on currently available evidence.
- Describe how a practical, dimensional approach can assist clinicians with identification of ADHD symptoms in patients with complex presentations, and inform appropriate management decisions.
A PubMed search for articles in English published between 1996 and 2016 was performed using “adult ADHD” as the main search term in combination with 29 others.* Clinical trials, clinical guidelines, meta-analyses and systematic reviews were selected for inclusion. A further manual search of selected article bibliographies afforded additional articles for inclusion, bringing the total number of included articles to 150.
The prevalence of ADHD in the general adult population has been estimated to be about 2.5% (95% confidence interval 2.1–3.1), with symptoms including: inability to pay attention to detail; difficulty organising tasks and/or activities; excessive talking and/or fidgeting; difficulty relaxing; a tendency to overwork; forgetfulness; and distractibility. Despite its relatively high prevalence, adult ADHD has been found to be under-diagnosed, particularly in females, who are more likely to have internalising symptoms which can easily be masked, compared with males who typically present with externalising symptoms.
Personal and societal costs associated with adult ADHD originate from impaired focus and attention; neuropsychological difficulties associated with a deficiency in inhibition, memory, executive functioning, decision making and emotional dysregulation; and educational difficulties. Over time, these symptoms may negatively impact relationship quality (e.g. in a community sample of 1001 adults, a significantly higher proportion of adults with ADHD had been divorced compared with those without ADHD [28% vs 15%; p≤0.001]) and employability (e.g. one study showed that adults with ADHD were less likely to be in full-time employment compared with those without ADHD [employment rate: 34% vs 59%, respectively; p<0.001]). Additionally, it has been suggested that adults with ADHD are twice as likely to be affected by psychiatric comorbidities and experience substance use disorders (SUDs).
It has been proposed that ADHD and psychiatric comorbidities stem from neurobiological similarities. Studies have indicated that differences in certain brain regions and abnormalities in neurotransmitters are involved in the development of ADHD and other psychiatric disorders.
In relation to diagnosing and treating ADHD symptoms in adults with comorbid psychiatric disorders, a review of the literature highlighted the following:
- Depression, anxiety disorders, bipolar disorder, SUDs and personality disorders are the most common psychiatric comorbidities associated with ADHD.
- Barriers to diagnosis and treatment arise from overlapping symptomatology between ADHD, psychiatric comorbidities and SUDs; e.g. in one study, 34% of patients referred for treatment-resistant depression also met criteria for ADHD.
- Misdiagnosis may result from physicians’ familiarity with common comorbid psychiatric disorders compared with ADHD.
- Treating ADHD symptoms may prevent worsening comorbid depression, bipolarity, anxiety and SUD.
- The authors have proposed three key questions that may enable clinicians to differentiate symptoms and identify ADHD: 1) “Have you had long-standing and consistent problems with attention and distractibility?”; 2) “Have your current complaints been present over the last 10 or 20 years?”; and 3) “If I could see you in the classroom when you were a child, what would you be like?”.
- If a possible ADHD diagnosis is suggested, an in-depth clinical interview using a screening instrument† should occur.
- Following a positive diagnosis, functional impairment and quality of life should be assessed.‡
- The choice of treatment should be based on efficacy, specifically in terms of functional outcomes, such as symptom reduction, improvement in daily functioning and increased quality of life. There is evidence to support the importance of a multimodal treatment approach using both pharmacological and non-pharmacological treatments to target the core symptoms of ADHD and for the improvement of functional outcomes.
- Pharmacological treatments – divided into two classes: 1) stimulants (e.g. methylphenidate, mixed amphetamine salts, lisdexamfetamine dimesylate); and 2) non-stimulants (e.g. atomoxetine). Both classes have associated side effects; however, studies have demonstrated their potential to limit both ADHD and some psychiatric comorbidity symptoms.
- Non-pharmacological treatments – divided into five classes: 1) psychoeducation (e.g. community resources and support groups); 2) behavioural interventions (e.g. ADHD coaching); 3) social interventions (e.g. parenting skills training); 4) psychotherapy (e.g. cognitive behavioural therapy); and 5) educational/vocational accommodations (e.g. academic remediation).
The authors concluded that although ADHD in the adult population is frequently unrecognised, under-diagnosed and under-treated, symptoms may be identified using a few high-yield clinical questions and validated assessment scales. They also emphasised that patients presenting with both ADHD and other psychiatric symptoms should be treated for the most severe disorder first, according to evidence-based guidelines.
Read more about adult ADHD and comorbid psychiatric disorders here
*PubMed search terms included “adult ADHD” in combination with: “anxiety”; “addiction”; “affective dysregulation”; “alcohol”; “bipolar”, “burden”; “catecholamine deficit”; “cocaine”; “cognition”; “depression”; “dimension”; “dimensional”; “disability”; “executive functioning”; “functioning”; “guideline”; “heritability”; “life expectancy”; “mania”; “marijuana”; “mortality”; “neurobiology”; “nicotine”; “personality disorders”; “prevalence”; “prevention”; “recommendation”; “risk factors”; or “substance use”
†Screening instruments include the Adult ADHD Self-Report Scale (ASRS), the Wender-Reimherr Adult Attention-Deficit Disorder Scale (WRAADDS), or the Conners Adult ADHD Rating Scales (CAARS). Another diagnostic tool, FAST MINDS (Forgetful; Achieving below potential; Stuck in a rut; Time challenged; Motivationally challenged; Impulsive; Novelty seeking; Distractible; Scattered) may also be used
‡Functional impairment and quality of life may be assessed using the Weiss Functional Impairment Rating Scale (WFIRS) and the Adult ADHD Quality of Life Scale (AAQoL)
Katzman MA, Bilkey TS, Chokka PR, et al. Adult ADHD and comorbid disorders: clinical implications of a dimensional approach. BMC Psychiatry 2017; 7: 302-316.