Is it a coincidence that half of the adults who report symptoms of attention-deficit hyperactivity disorder (ADHD) also report co-existing substance-abuse disorders, including alcoholism?
Does one condition increase the risk for the other? Or is there some genetic link between inattention, motor hyperactivity, impulsiveness, and alcoholism? Or is it some combination of the two?
Some researchers believe they have identified a distinct phenotype or “profile” of individuals with co-existing ADHD and alcoholism.
Although prior studies have suggested a genetic commonality of ADHD and alcoholism, a University of Regensburg study found no significant contribution of two specific candidate genes, the promoter polymorphism of the serotonin transporter gene (5-HTT) and the 5-HT2c receptor Cys23Ser polymorphism.
ADHD Symptoms and Alcohol Abuse
“Our results indicate that individuals with persisting ADHD symptoms in adulthood seem to be at high risk of developing an alcohol-use disorder,” said Monika Johann, a medical doctor and research associate at the University of Regensburg and first author of the study. “Moreover, there is evidence for a highly increased severity of alcohol dependence in subjects with ADHD.”
Researchers examined 314 adult alcoholics (262 males, 52 females) as well as 220 unrelated healthy control subjects, all of German descent. Each participant was assessed for psychiatric disorders, such as substance-use disorders (including alcoholism), ADHD, and antisocial personality disorder (APD).
Sources of Genetic Liability
Patients with a history of major psychiatric disorders, including depression and schizophrenia, and those with addictions to drugs other than alcohol and nicotine were excluded from the investigation. Genotyping was performed without knowledge of diagnostic status, with a focus on the 5-HTT promoter and the 5-HT2c Cys23Ser polymorphism.
“Prior neuroendocrine challenge studies with a drug called fenfluramine in subjects with ADHD or alcoholism revealed similar differences in the serotonergic neurotransmission when compared to normal subjects,” explained Johann. “The usual response to fenfluramine administration is a measurable increase in the circulating prolactin. This usual increase is blunted in subjects with ADHD or alcoholism. The main structures responsible for the fenfluramine-induced prolactin release are the 5-HTT and the 5-HT2c receptors. Therefore, both seemed plausible as overlapping sources of genetic liability of ADHD and alcoholism.”
Genetic Predisposition Not Found
Neither of them, however, appear to be genetic risk factors in the sample examined. “Our data demonstrate that the 5-HTT promoter and the 5-HT2c Cys23Ser polymorphism do not contribute to the putative common genetic predisposition for ADHD and alcohol dependence,” said Johann. “However, several other candidate genes have yet to be investigated.”
Nonetheless, the findings do indicate a distinct phenotype, a way to measure an observable trait or behavior.
The Regensburg study has found that adult alcoholics with ADHD had a significantly higher daily intake of alcohol per month, an earlier age of onset of alcohol dependence, a higher frequency of thoughts about suicide, a greater number of court proceedings, and a greater occurrence of APD.
Thus, despite the lack of support for a common genetic predisposition, “the data show once again that to have ADHD means to be at high risk for developing alcohol dependence,” said Ema Loncarek, a medical doctor, and clinician at the psychiatric clinic of the University of Regensburg. Loncarek works on a ward for illegal drug addiction, providing detoxification and therapy.
ADHD Addicts Difficult to Handle
“Dr. Johann’s findings of a phenotype are very close to what we see in drug addicts with ADHD, and what has been described before by other authors. We see on a regular basis that drug addicts with ADHD are difficult to handle. They start to abuse drugs earlier than other people, change earlier to ‘hard’ drugs, take longer to start treatment, and take longer to successfully finish therapy.”
The study found that within this group of alcoholics, subjects with ADHD in adulthood are:
- Five to 10 times more frequent than the general population
- Four years younger at the onset of alcoholism
- Drank 50 grams more of alcohol per day
- Twice as likely to have a family history of alcoholism
- Three times higher rate of antisocial personality disorder
- Seven times more likely to have faced court proceedings
- More than twice the frequency of suicidal thoughts
Specialized Treatment Needed
Both Johann and Loncarek spoke of a need for the development and evaluation of specialized treatment programs that address “phenotypical specifics” as well as co-existing disorders such as alcoholism and ADHD. While pharmacological remedies, they noted, have been extensively evaluated for the treatment of ADHD in childhood, little attention has been given to substance-abusing individuals with ADHD in adulthood.”
“ADHD seems to be highly underestimated in adulthood,” said Johann, “yet seems to be an important risk factor for the development of alcohol dependence.”
By Buddy T, Reviewed by Richard N. Fogoros, MD