The relationship between ADHD and substance use disorder
Attention-deficit/hyperactivity disorder (ADHD), a neurodevelopmental disorder that begins in childhood and persists into adulthood in more than 50% of cases, is a risk factor for the development of substance use disorder (SUD). Individuals with ADHD often experience an early onset of substance use and a rapid transition from initial use to addiction. Furthermore, individuals with both ADHD and SUD exhibit more complex and chronic substance use patterns, as well as a higher frequency of polysubstance use, compared to individuals with SUD without ADHD. Other psychiatric disorders are also more frequently observed in these cases, notably antisocial and borderline personality disorders, mood disorders, and anxiety disorders.
Regarding the type of substances consumed, adults with ADHD use the same drugs as the general population: cannabis and cocaine are the most common illegal drugs; and the most commonly used legal substances are alcohol and tobacco, with three times more likely to smoke than the general population.
The treatment of people affected by substance use disorder and ADHD is complex , and difficulties in making an adequate diagnosis and in offering comprehensive and individualized treatment, both pharmacological and psychological, are frequent (Crunelle et al., 2018).
Prevalence of ADHD and substance use disorder
ADHD is therefore a risk factor for developing a substance use disorder later in life. A meta-analysis estimated the prevalence of ADHD in adults with substance use disorders at 23.1%. However, a subsequent international multicenter study, which evaluated 1,276 individuals, reported that 13.9% of people seeking treatment for substance use also had ADHD. Both studies indicate that the prevalence of ADHD in adults is significantly lower among those seeking treatment for alcohol use (Van Emmerik et al., 2012) (Van de Glind et al., 2014).
Hypothesis of causality in the appearance of ADHD and substance use disorder
Several risk factors —genetic, neurobiological, and psychosocial—have been identified that contribute to the comorbidity of substance use disorder and ADHD, but causal links have not been established. It has been proposed that there is a genetic predisposition in individuals with ADHD to develop a substance use disorder and that there is a shared neurobiological substrate. At a more behavioral level, it has been described that the impulsivity characteristic of ADHD can contribute to the development of a substance use disorder due to increased risk-taking behaviors and difficulties in managing cravings (an intense and uncontrollable desire to break abstinence). Finally, the self-medication hypothesis proposes that individuals with pathological emotional states use substances to alleviate their emotional distress.
Adolescence, a critical period for drug use
Adolescence is a crucial stage of life characterized by a tendency toward experimentation and a tendency to minimize risk. For this reason, risky behaviors, including drug use, are common. It is important to know that the presence of ADHD increases the risk of chronic drug use. Conduct disorder and oppositional defiant disorder are common among adolescents with ADHD, and in these cases, the risk of addiction is even higher. Therefore, prevention, early detection, and appropriate treatment of both disorders are even more critical among adolescents.
The impulsivity characteristic of ADHD can contribute to the development of a substance use disorder, due to the increase in risky behaviors and difficulties in managing cravings.
How to diagnose ADHD in adults with substance use disorder?
Because ADHD can determine the course of addiction, it is important to conduct early diagnosis and systematic screening for ADHD among people seeking help for substance use disorders, even if they focus their demands on substance use disorders and do not spontaneously refer to ADHD symptoms.
The diagnosis must be clinical, and the most important element is a complete and thorough diagnostic interview. Questionnaires and interviews can contribute to the diagnostic process. These instruments are very useful; however, the results should be interpreted with caution, and the psychometric properties of these instruments in populations with addictions must be understood.
Some frequently used questionnaires are the Adult ADHD Self-Report Scale (ASRS-SV) and the Wender Utah Rating Scale (WURS). A positive screening result should always be clinically evaluated, for which diagnostic interviews are useful (Daigre et al., 2015) (Van de Glind et al., 2013).
The diagnostic interview should include an assessment of current ADHD symptoms, childhood ADHD symptoms, family history of ADHD and substance use disorder, school and work history, romantic relationships, and other comorbid physical and psychiatric conditions. It is also important to include environmental and psychosocial factors to gain a comprehensive perspective for diagnosis and to identify risk and protective factors. Furthermore, ADHD symptoms should be evaluated throughout the individual's lifespan, inquiring about these symptoms and their impact during periods of abstinence from substance use. Given that the DSM-5 specifies that symptoms must begin before age 12, interviewing parents or siblings is highly beneficial, as they can provide additional information about the individual's childhood.
It is important to include environmental and psychosocial factors to have a broad perspective when making the diagnosis and to be able to identify risk and protective factors.
The diagnostic process should begin as soon as possible, provided there are no severe withdrawal or intoxication symptoms. The preliminary diagnosis should be reassessed during the course of treatment, as should the presentation of ADHD symptoms, since these may change with treatment for the substance use disorder (SUD) or specific ADHD treatment. The most frequently used semi-structured interview is the Interview Diagnosis of ADHD in Adults DIVA 2.0 , Conners' Adult ADHD Diagnostic Interview for DSM-IV (CAADID) and the Psychiatry Research Interview for Substance and Mental Disorders (PRISM) .
Several factors can complicate diagnosis and lead to over- or underdiagnosis, with undiagnosed cases of ADHD becoming increasingly common. Table 1 below summarizes the considerations to keep in mind when conducting a diagnostic evaluation.
| Factors that complicate the diagnosis of ADHD in TUS |
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| To avoid overdiagnosis, you should: |
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| Underdiagnosis can occur when: |
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Treatment of ADHD in people with substance use disorder
Appropriate treatment for ADHD in individuals with substance use disorder comprises several components, including psychoeducation, medication, cognitive behavioral therapy (which can be delivered individually or in groups), peer support, and motivational training . In adults with ADHD and substance use disorder, research suggests that combined treatment with medication and psychological therapy improves outcomes compared to medication alone.
ADHD treatment should be integrated with substance use disorder treatment, and vice versa . Providing comprehensive treatment, rather than parallel care between two teams, is crucial because ADHD symptoms can interfere with addiction treatment, and conversely, substance use disorder symptoms can complicate ADHD treatment.
Pharmacological treatment
It is advisable to begin treatment for substance use disorder (SUD) immediately and then, as soon as possible, begin treatment for ADHD. However, it should be noted that effective ADHD treatment generally does not lead to an improvement in the substance use disorder, which underscores the need to treat both disorders appropriately.
Current studies show that medication is moderately effective in reducing ADHD symptoms in individuals with substance use disorders and ADHD , with an average effect size of 0.4-0.5. Regarding pharmacological treatment, it should be remembered that its positive effects are increased when combined with psychotherapy, that ADHD medication alone is not effective in reducing substance use, and that it can cause adverse effects and treatment discontinuation.
Treating ADHD and substance use disorder in a comprehensive manner, rather than in parallel, is important because the symptoms of one disorder can complicate or interfere with the treatment of the other.
Regarding methylphenidate, controlled clinical trials with standard short- and long-release doses show that ADHD and substance use disorder (SUD) symptoms do not improve, or only ADHD symptoms improve, but not drug use (Coghill et al., 2014). However, two clinical trials testing higher doses of methylphenidate, up to 180 mg/day, found a reduction in ADHD symptoms and a decrease in the reinforcing effect of cocaine and amphetamine use in adults with ADHD and SUD, with a reduction in cocaine use observed (Levin et al., 2018). Furthermore, moderately high doses of extended-release amphetamines (60–80 mg/day) have shown effectiveness in reducing ADHD symptoms and cocaine use in individuals with this comorbidity.
Regarding other medications, pemoline has been associated with a reduction in ADHD symptoms, but not in drug use. Treating this comorbidity with atomoxetine has shown a significant reduction in ADHD symptoms and has also been associated with a decrease in cravings and alcohol consumption. In recent years, lisdexamfetamine has also demonstrated effectiveness in the treatment of ADHD. Both lisdexamfetamine and methylphenidate have shown similar efficacy in the treatment of ADHD. In a comparative controlled clinical trial between the two medications (Coghill et al., 2014), the therapeutic results found were similar in those cases that had not previously been treated. In a second controlled clinical trial comparing more variables (Banaschewski et al., 2019), some scores were favorable with lisdexamfetamine and others with methylphenidate. Regarding its efficacy in reducing substance use, it has also demonstrated effectiveness. It could be concluded that, in terms of therapeutic effect, both drugs are similar. Another drug that has been widely used recently is guanfacine, which has shown efficacy in people with ADHD and tics, but has limited effectiveness in reducing substance use.
As always, negative results should be interpreted with caution, because some of these studies have reported promising results regarding substance use in secondary analyses.
Safety of pharmacological treatment for ADHD in adults with substance use disorder
Although ADHD treatment can be effective among people with substance use disorder who have this comorbidity, especially when using higher doses of psychostimulants , many clinicians are still reluctant to prescribe appropriate ADHD treatment to people with substance use disorder.
During treatment with psychostimulants in individuals with substance use disorders (SUDs), medication misuse should be monitored, especially in adolescents and young adults. Immediate-acting preparations should be avoided, and long-acting formulations should be preferred, particularly methylphenidate (OROS) and lisdexamfetamine, which have considerably low rates of misuse. Adverse effects are not increased in individuals with ADHD and a substance use disorder compared to those with ADHD without the latter. The literature has not reported an increase in substance use due to stimulant prescription in this population. However, one case of psychotic symptoms secondary to a possible dose-dependent interaction between disulfiram and methylphenidate has been described.
On the other hand, ADHD treatment with psychostimulants does not cause substance use disorders in adults without prior addiction. Regarding the prevention of substance use disorders, it has been described that stimulant treatment of children with ADHD may have a protective effect against the development of addictions, especially if children receive treatment from an early age and for a sufficient period of time.
Finally, in the prescription of stimulants, as with any other controlled drug, clinical judgment should be used to assess the risks versus benefits of the medication.
Psychosocial interventions
Few studies have focused on the psychosocial treatment of individuals with substance use disorders (SUDs) and ADHD compared to pharmacological interventions. However, clinicians agree that appropriate treatment includes a psychotherapeutic approach .
A clinical trial compared the effectiveness of integrated cognitive behavioral therapy for treating both substance use disorder and ADHD with therapy focused solely on substance use. Both interventions were found to be effective in reducing drug use when comparing pre- and post-treatment data. Furthermore, the therapy integrating treatment for both disorders significantly reduced ADHD symptoms. This suggests that integrating the ADHD component for those who require it does not diminish the expected effects of interventions focused on addiction (Van Emmerik-van et al., 2019).
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