Are Some Individuals Diagnosed With ADHD Prone to Alcohol Abuse?

Overview and Hypothesis

A mutation in the DRD4 found in some individuals diagnosed with ADHD may be part of the reason why some individuals with ADHD are more prone to the development of alcohol abuse. Those diagnosed with ADHD already have a lower level of the naturally occurring neurotransmitter dopamine and are often treated using stimulants that help to regulate these levels. Those with this mutation however require an even higher level of dopamine to be reached before a decrease in their symptoms is seen. Along with this biological mutation, a cognitive difference in thinking and planning may further solidify this vulnerability some individuals with ADHD may have toward alcohol abuse. A deficiency in functionality of the prefrontal area of the brain designed for planning and reasoning may cause an individual to think less clearly about his or her actions and the best methods to accomplish his or her goals. This cognitive deficit was found in some individuals with ADHD. It is proposed that these individuals may turn to alcohol to try to deal with the symptoms of ADHD and not clearly measure or understand the consequences of dealing with their symptoms in this manner. Therefore, those individuals diagnosed with ADHD with the mutation in DRD4 (requiring an increased need for dopamine to calm their symptoms) who also have problems with reasoning and planning, may cope with the symptoms of ADHD by self-medicating through alcohol, which provides them with increased levels of dopamine. If done repeatedly for these reasons, this self-medication could result in alcohol abuse.

It is hypothesized then, that a combination of these two variables may predispose some individuals, but not others, with ADHD to this downhill spiral of alcohol abuse, accounting for the discrepancies found in the research surrounding this topic.

A Biological Vulnerability? Dopamine, Alcohol, and DRD4

As further research continues to uncover new findings regarding the biology of ADHD, it is still unclear as to what systems exactly are affected in this disorder. One area that has repeatedly demonstrated an association with the symptoms of ADHD, however, has been the dopamine system (Ohlmeier et al., 2008). One example of this association is that individuals with ADHD consistently show a lower amount of dopamine in the prefrontal area of the brain than those without the diagnosis of ADHD (Comings et al., 2005). As this deregulation of dopamine seems to be a prime factor influencing symptoms of ADHD, stimulus drugs such as methylphenidate (Ritalin) are normally prescribed to regulate amounts of dopamine in various areas (Ohlmeier et al., 2008). The use of stimulants both encourages the production of dopamine and inhibits the reuptake of it in the prefrontal area of the brain, resulting in a prolonged exposure to the neurotransmitter (Nolen-Hoeksema & Rector, 2008). Interestingly, substances such as alcohol have the same effects on dopamine as stimulants in the brain. When individuals consume alcohol, the dopamine neurons are stimulated and components of alcohol also inhibit the reuptake of dopamine in the synapse. In addition, dopamine is involved in the reward pathways of our brain; increased amounts of dopamine can have the effects of pleasure and thus lead to reinforcement of behaviors that increases levels of dopamine such as drinking (Nolen-Hoeksema & Rector, 2008). This relationship between ADHD and lowered dopamine levels, and alcohol ingestion and increased levels of dopamine becomes particularly important in research concerning ADHD and risks of alcohol abuse. It seems plausible that individuals with ADHD may use alcohol to increase levels of dopamine to reduce their symptoms. The fact that dopamine is part of the reward pathway is a further incentive for these individuals to continue this method of dealing with symptoms. However, not all individuals with ADHD who drink develop an abusive behavior toward alcohol consumption, so there must be an additional mediating factor. This factor may involve the DRD4 gene.

Some studies have recently found a link between the D4 dopamine receptor and ADHD. According to these studies, various alleles such as the 7-repeat allele (Faraone, Doyle, Mick, & Biederman, 2001) and the 10 allele in the DRD4 gene (Comings et al., 2005) are more commonly found in individuals diagnosed with ADHD. The implication of this mutation is that it results in a system that is more tolerant against the effects of dopamine. This is of particular importance in this area of alcohol abuse as those with ADHD with this mutation in the DRD4 gene may require even higher amounts of dopamine in the system to gain the same reward effects others receive with a much lower level of dopamine. One group of researchers’ proposal of the “reward deficiency syndrome” may explain why this mutation in the DRD4 gene could lead to alcohol abuse in those with it. The researchers believed that a genetic abnormality in the dopamine gene resulted in a deficiency of this gene to produce pleasure/rewards and argued that this could be the reason why some individuals seek out ways to increase stimulation of the reward pathways through drugs, alcohol and risky behaviors (Comings et al., 2005). This theory could hold true for abnormalities of DRD4, where increases in the 7- or 10-allele of the DRD4 gene could lead to individuals consuming more alcohol to obtain the desired effects (such as relief from symptoms of ADHD). One study by Hamarman, Fossella, Ulger, Brimacombe, and Dermody (2004) found an association between the 7-repeat allele of DRD4 and level of stimulant required for reductions in ADHD symptoms. The study showed that when individuals had the 7-repeat allele of DRD4 present (DRD4 mutation) they required a higher dosage of stimulant drugs to see the same results as those individuals without the 7-repeat allele of DRD4 (Hamarman et al., 2004). Another study focused on the 7-repeat allele of the DRD4 gene and its possible implications in craving alcohol after consumption of alcohol. The researchers concluded that those individuals with the DRD4 gene mutation had a higher level of craving for alcohol after they had consumed it than those without the DRD4 gene mutation (Hutchison, McGeary, Smolen, Bryan, & Swift, 2002).

It is interesting then that other studies have found that the use of stimulants in individuals diagnosed with ADHD not only reduces symptoms but also reduces these individuals’ susceptibility to develop substance addictions (Ohlmeier et al., 2008). According to this research, those taking stimulant drugs to reduce symptoms of ADHD should not have an increased susceptibility to developing alcohol abuse. Perhaps the reason for these findings is that those who take stimulus drugs such as Ritalin for symptoms of ADHD do not become addicted to alcohol as often because they have already found a way to reduce their symptoms through the use of prescription drugs and do not feel the need to turn to alcohol to self-medicate (Ohlmeier et al., 2008). However, if drinking and stimulant drugs increase levels of dopamine in the brain, then perhaps those individuals who do not use stimulants turn to alcohol because they do not know how else to cope with their symptoms or find that it works equally well but is a more socially acceptable way to behave (drinking vs. taking prescription drugs for a disorder).

It seems then, that it is not simply a mutation in the DRD4 gene that has to be present for this predisposition of alcohol abuse, but along with this mutation must come cognitive reasoning for using substances as a way to self-medicate without foresight into the consequences of this behavior.

A Cognitive Aspect Too? ADHD, Planning and Reasoning, and Alcohol Abuse

As mentioned earlier, ADHD is thought to result in part from a deficiency in levels of dopamine in the prefrontal area of the brain. This area is involved in planning and reasoning behavior. A study was done on individuals with ADHD and cognitive tasks involving the prefrontal area of the brain. The researchers found that those who performed poorly on these tasks were more likely to develop problems with alcohol (Span & Earleywine, 2004). This study was redesigned to include only women with ADHD, and the findings were repeated (Span & Earleywine, 2004). These findings suggest that better performance on tasks involving the prefrontal cortex may mediate effect of drinking behaviors in those with ADHD. The reason for this relationship may simply be that those individuals with ADHD who have lower function in the prefrontal cortex may turn to substances such as alcohol to deal with their symptoms in the short term and be unable to plan a different way to deal in the long term or even have the desire to plan a different way to deal as they do not see the consequences of their choice to self-medicate. However, those with ADHD who have better performance in this area of the brain may not be prone to develop alcohol abuse because they do not resort to alcohol as a means of dealing with their symptoms and are thus less vulnerable to the development of alcohol abuse.

Summing Up, Future Directions, and Implications

As the research above suggests, there is no simple correlation between ADHD and alcohol abuse. Although some studies have found correlations, others have found no significant relationship at all. This discrepancy in research results begs the following question: What is causing some studies to find a relationship? The present research shows that there are at least two possible mediating variables in individuals with ADHD that may cause a predisposition to alcohol abuse in those with them. Individuals diagnosed with ADHD who possess a mutation in the DRD4 gene and have a lower level of functioning in the prefrontal area of the brain may be at a higher risk for developing alcohol abuse when they turn to alcohol to deal with the symptoms of ADHD without fully considering the consequences associated with this self-medicating approach. Future studies should test this theory to see whether those diagnosed with ADHD with the DRD4 gene mutation and lower prefrontal functioning are at higher risk for the development of alcohol abuse. If a correlation exists, targeting these individuals and showing them better means to deal with their symptoms before alcohol abuse surfaces may help to prevent this behavior. Treatment could also be used with those individuals who have already developed a drinking problem in response to their symptoms of ADHD. Allowing these individuals to develop other means of coping and showing them that their drinking behavior is making their life worse, and not better, and is only temporarily masking the problems they face can help to support better planning and use of tools to help them deal successfully with their symptoms. Although it may not be possible to intervene at the biological level, there is still hope for interventions at the cognitive level if this correlation exists.