The presence of comorbid disorders is often the rule rather than the exception in individuals with ADHD. Of particular concern is problematic substance use; alcohol, cannabis, cocaine, and nicotine represent some of the most commonly abused substances. Elevated substance use significantly complicates a patient’s symptom presentation, making the accurate diagnosis, prognosis, and treatment of ADHD challenging even for the most skilled practitioners.
The link between ADHD and substance use disorders
Children with ADHD are at increased risk for alcohol use disorder as they get older, and they are more than twice as likely to develop nicotine dependence and marijuana or cocaine abuse or dependence (Figure). Approximately 15% of adolescents and young adults with ADHD have a comorbid substance use disorder (SUD), while 11% of individuals with an SUD also meet the criteria for ADHD.1 Findings indicate that the overlap between these disorders is not random, and several explanations have been posited for their link.
ADHD and SUD have been described as disorders of disinhibition, which suggests an underlying vulnerability that is shared by both disorders. Alternatively, features of ADHD, such as impulsivity, may increase the risk of initiating substance use. In fact, children with ADHD are significantly more likely to try a range of substances during their lifetime compared with their non- ADHD counterparts (see Figure).
The mechanisms underlying the increased risk of SUD among those with a history or current diagnosis of ADHD are not well understood. Persistent ADHD, which might be a marker of increased vulnerability and/or of reduced access or responsiveness to intervention, is associated with much higher rates of SUD.2 The high co-occurrence between ADHD and SUD merits special consideration.
Issues in identifying suspected SUD
Assessment for ADHD requires the ability to distinguish between ADHD and other disorders that demonstrate significant symptomatic overlap. Among individuals who present with active substance abuse, it is critical to distinguish between a valid ADHD diagnosis and substance-induced impairments that can negatively affect attention, concentration, and impulsivity. Many psychoactive substances have acute effects that can mimic the symptoms of ADHD, such as chronic marijuana use, which has been associated with deficits in problem-solving, organization, and sustained attention that may persist even after 3 weeks of abstinence. Because of this, practitioners might want to prioritize the treatment of substance use and then re-evaluate patients for ADHD after a period of prolonged abstinence.
Unfortunately, this approach is sometimes not feasible, particularly for patients who present with significant and untreated ADHD symptoms that may impair the ability to engage in and benefit from SUD treatment. Thus, a comprehensive evaluation of ADHD symptoms during prior periods of abstinence may be the next best approach for assessing co-occurring SUD and ADHD, with a focus on whether the ADHD symptoms preceded the onset of substance use. While this is a reasonable recommendation, this approach is not without challenges, as it requires patients to recall the onset and severity of their initial symptoms. This may be especially challenging for patients with ADHD and substance abuse because both are associated with neurocognitive deficits.
Ms. Galán is a graduate student in the joint clinical and developmental psychology PhD program at the University of Pittsburgh; Dr. Humphreys is Postdoctoral Fellow, Department of Psychology, Stanford University.
The authors report no conflicts of interest concerning the subject matter of this article.
1. Kessler RC, Adler L, Barkley R, et al. The prevalence and correlates of adult ADHD in the United States: results from the National Comorbidity Survey Replication. Am J Psychiatry. 2006;163:716-723.
2. Hechtman L, Swanson JM, Sibley MH, et al. Functional adult outcomes 16 years after childhood diagnosis of attention-deficit/hyperactivity disorder: MTA results. J Am Acad Child Adolesc Psychiatry. 2016;55:945-952.
3. Humphreys KL, Eng T, Lee SS. Stimulant medication and substance use outcomes: a meta-analysis. JAMA Psychiatry. 2013;70:740-749.
4. Kalbag AS, Levin FR. Adult ADHD and substance abuse: diagnostic and treatment issues. Subst Use Misuse. 2005;40:1955-1981.
5. Riggs PD, Winhusen T, Davies RD, et al. Randomized controlled trial of osmotic-release methylphenidate with cognitive-behavioral therapy in adolescents with attention-deficit/hyperactivity disorder and substance use disorders. J Am Acad Child Adolesc Psychiatry. 2011;50:903-914.
6. Lee SS, Humphreys KL, Flory K, et al. Prospective association of childhood attention-deficit/hyperactivity disorder (ADHD) and substance use and abuse/dependence: a meta-analytic review. Clin Psychol Rev. 2011;31:328-341.