ADHD and Substance Abuse
Summarized by Dominic Ferro, M.D.
Daniel Pimstone, M.D. and Itai Danovich, M.D. spoke about the dilemma of treating adolescents with both Attention Deficit Hyperactivity Disorder (ADHD) and Substance Use Disorders: the most effective treatment for ADHD is with stimulants, which are themselves substances of abuse.
Having both ADHD and substance abuse affects the outcome of both conditions. 30-65% of ADHD patients have impairing symptoms that persist into adulthood, most often symptoms of inattention. These patients have higher rates of divorce, arrest, and speeding. They have higher rates of tobacco dependence as well. In addition, ADHD predicts worse substance abuse outcomes as ADHD patients develop substance abuse disorders at a younger age. They progress more rapidly from experimentation to dependence and quickly move from one drug to others. They are less responsive to treatment and relapse more quickly.
Pertinent to the treatment dilemma is the fact that stimulants are not the most commonly abused substances by adolescents with ADHD. Surveys have shown that 67% used cannabis and 40% used alcohol as their drug of choice. Only 21% abused stimulants. While adolescents with ADHD have similar rates of substance use disorders as other adolescents, they progress to adult chemical dependency disorders at a substantially higher rate.
Looking at populations of adolescent substance abusers, ADHD is an independent risk factor for substance abuse. 10% of adolescent substance users have comorbid ADHD and 25% had ADHD and took medication during earlier childhood. Adolescents with alcohol dependency had the highest rate of comorbid ADHD; those with opiate or cocaine dependence had lower rates.
Dr. Pimstone discussed different theories to explain the correlation between ADHD and substance abuse. One possibility is that children with ADHD have a developmental vulnerability to substance abuse. For instance, there are higher rates of substance abuse disorders among first degree relatives of children with ADHD. Also, children with ADHD have higher rates of social problems and school difficulties, both of which are known risk factors for substance abuse disorders. Similarly, the impulsivity and sensation seeking which are common in ADHD increase the risk of substance abuse.
Another possible explanation is that substance abuse and ADHD share common endophenotypes, genetic predispositions to both disorders. The best evidence for such endophenotypes is found in the dopamine system that results in a theorized hypodopaminergic state. Other possible shared endophenotypes include cognitive processing deficits and selective attention, excessive arousal with consequent aggression and impulsivity, impaired behavioral disinhibition, and impaired affective regulation that results in insensitivity to aversive conditioning and rewards.
A third possible explanation is that adolescents with ADHD use substances to modulate psychiatric symptoms, in other words the “self medication” theory. Surveys of patients indicate that they believe that this is the best explanation for their experience. Attentional dysfunction is a predictor of initiation and maintenance of tobacco use, which patients describe as helpful with focus. Alcohol and cannabis may ameliorate the commonly reported subjective symptoms of anxiety and dysphoria or they may help with disordered sleep. Adolescents with ADHD more often reported using substances to alter mood instead of trying to get high. Illicit substance use also reportedly improved the self image of ADHD adolescents.
A final explanation is that early exposure to stimulants results in substance abuse, the so-called “priming phenomenon”. Dr. Danovich described some of the factors that support this theory, in particular the cases of later stimulant abuse. The pharmacokinetics of stimulants, especially their rapid rate of onset, does seem to play a role. For instance, the subjective effect is less evident when stimulants are taken orally vs. intravenously, the latter of which had linear dose response of “liking” the drug. Compared to extended release preparations, short acting stimulants have a greater likelihood of developing a reinforced pattern of use was in animal models. Animal models also demonstrate patterns of sensitizing and dependence on stimulants.
However, in humans, early stimulant initiation has not led to measurable negative outcomes. In fact, the rate of substance use disorders was decreased among ADHD adolescents taking prescribed stimulants than those who do not. On further analysis, a comorbid conduct disorder was more predictive of the observed substance abuse into adulthood. However, Dr. Danovich concluded that there is no good evidence that substance abusing teens could be safely treated with stimulants, and it is known that some patients will divert or abuse prescribed medication.
Dr. Pimstone opined that neuropsychological evaluation is not helpful when an adolescent is actively using, and that the best tool is a thorough clinical assessment with an eye toward the timing of symptoms. He recommended establishing separate timelines for the symptoms of ADHD and of the substance abuse disorder. He also recommended performing the neuropsychological assessment after several weeks of abstinence.
With regard to treatment, these adolescents should be engaged with enhanced psychosocial interventions in integrated and structured care with frequent re-evaluation. Dr. Danovich recommended minimizing the use of reinforcing medications, for instance starting with long acting stimulant preparations, or considering Strattera and other non-stimulant medications. He also recommended involving the adolescent’s support network to assist in close monitoring. Since there are separate treatment systems and funding sources for mental health, substance use, and medical care, treatment is even more challenging since contact between providers in different systems is needed to effectively manage these cases.