ADHD medication and SUDs
All physicians who treat patients with attention-deficit/hyperactivity disorder get an earful from parents and patients who fear that the drugs will lead to addiction to stimulants. Reassuring evidence that this isn’t the case comes from a massive study of nearly 3 million adolescent and adult ADHD patients, median age 21, in a U.S. commercial health care claims database. The study endpoint was visits to emergency departments related to substance use disorders during 16 months of follow-up.
In within-individual comparisons, male patients had an adjusted 35% reduction in the likelihood of trips to the ED for substance use events during the months they received stimulant medications or atomoxetine, compared with the months they were off ADHD medication. Females had a 31% reduction during their on-treatment months (Am J Psychiatry. 2017 Sep 1;174[9]:877-85).
“That’s the kind of information I like to share with my patients,” Dr. Gorwood commented. “It’s very easy to understand, and it gives them objective information that – although they may find surprising – treatment protects against addiction rather than leading to addiction.”
Divorce and new AUD
A Swedish national registry study of 942,366 married people born in 1960-1990, none with a history of AUD when they tied the knot, documented that divorce predicted a six- to sevenfold increase in new-onset AUD, compared with that of individuals who stayed married. Remarriage cut that risk by 50%-60% relative to those who did not remarry.
The relationship between marriage, divorce, and AUD was more complex than that, however. The level of drinking actually started to increase several years before divorce.
“A lot of patients will say, ‘Doctor, I’m drinking so much now because I’ve lost my wife, my life is miserable, and the only thing I have now is alcohol to make things feel better.’ But we could propose a different statement: ‘Maybe you got divorced because you drank too much alcohol.’ We wouldn’t say that to patients, of course, but we could help them to recognize their own paradoxical approach,” Dr. Gorwood said.
Widowhood was associated with a roughly fourfold increased risk of new-onset AUD, according to an article in the American Journal of Psychiatry (2017 May 1;174[5]:451-8).
Study of pathological gambling
A German multicenter team set out to identify genetic pathways involved in pathological gambling. They found a strong association with alcohol dependence, providing novel evidence of genetic overlap between a substance- and non–substance-related addiction. Unexpectedly, they also identified a shared genetic pathway between pathological gambling and Huntington’s disease that will provide a rich new avenue of research. Their results were published in the journal European Psychiatry (2016 Aug;36:38-46).
Gene implicated in alcohol use disorder
For several years, cardiologists have been agog over the unprecedented LDL cholesterol–lowering ability of a novel class of medications that inhibit the protein produced by the PCSK9 (proprotein convertase subtilisin/kexin 9) gene, which slows removal of LDL from the circulation. Ongoing studies of the PCSK9 inhibitors evolocumab and alirocumab are widely expected to report reductions in cardiovascular event rates far beyond what is achievable with statins.
Now investigators at the U.S. National Institute on Alcohol Abuse and Alcoholism have conducted a genomewide methylomic variation study that showed PCSK9 expression in the liver is dysregulated in patients with alcohol use disorder. They coupled this finding with a translational study in a mouse model of alcohol use disorder in which they demonstrated that alcohol exposure leads to PCSK9 downregulation, with resultant lowering of LDL.
Taken together, the results, published in Molecular Psychiatry (2017 Aug 29. doi: 10.1038/mp.2017.168), suggest that epigenetic regulation of PCSK9 by alcohol is a dynamic process in which exposure to small amounts of alcohol leads to less PCSK9 gene expression, less methylation, and lower LDL, while chronic heavy use leads to greater gene expression, unfavorable lipid levels, and eventually to low PCSK9 protein levels as a result of hepatotoxicity.
MicroRNA-495 and cocaine
Using genomewide sequencing techniques, investigators zeroed in on a specific microRNA known as miR-495 as an important posttranscriptional regulator of the expression of genes included in KARG, the Knowledgebase for Addiction Related Genes database. This small RNA is highly expressed in the nucleus accumbens, a key area of the brain involved in motivation and reward.
In rodent studies, the researchers showed that administration of cocaine rapidly downregulated miR-495 expression in the nucleus accumbens with an accompanying increase in expression of addiction-related genes known to be involved in specific substance use disorder–related biologic pathways. Moreover, when the investigators induced miR-495 overexpression in the nucleus accumbens, the animals lost motivation to seek and self-administer cocaine without having any effect on food-seeking, suggesting miR-495 selectively affects addiction-related behaviors, according to results of a study published in Molecular Psychiatry (2017 Jan 3. doi: 10.1038/mp.2016.238).
“I found this really convincing. There is converging evidence that we’re going to hear a lot more about miR-495 later on,” Dr. Gorwood said.
He reported having no financial conflicts of interest regarding his presentation.