Genetic variants associated with enjoying the effects of d-amphetamine—the active ingredient in Adderall—are also associated with a reduced risk for developing schizophrenia and attention deficit hyperactivity disorder (ADHD), report scientists from the University of Chicago in the Proceedings of the National Academy of Sciences on April 7. The results support a long-standing hypothesis that dopamine, the neurotransmitter connected with the euphoric effects of amphetamine, is related to schizophrenia and ADHD.
“Some of the variants that make you like amphetamine also appear to make you less likely to develop schizophrenia and ADHD,” said study leader Abraham Palmer, PhD, associate professor of human genetics at the University of Chicago. “Our study provides new insights into the biology of amphetamine and how it relates to the biology of risk for these psychiatric diseases.”
Palmer and his team previously conducted a genome-wide association study (GWAS) to identify genetic variants associated with experiencing the euphoric effects of amphetamine, which is thought to affect risk for drug abuse. Almost 400 volunteers were given d-amphetamine in a double-blind, placebo-controlled experiment.
They were then asked to report how the drug made them feel using carefully designed questionnaires. The researchers measured genetic differences between these subjects at approximately a million sites throughout the genome to identify variations in the DNA code known as single nucleotide polymorphisms, or SNPs. They assessed the relationships between each of these SNPs and sensitivity to amphetamine.
Using data from other large-scale GWAS studies, the team examined these same SNPs for possible overlapping associations with psychiatric disorders. Through rigorous statistical testing they found that an unexpectedly large number of SNPs were associated with both sensitivity to amphetamine and risk of developing schizophrenia or ADHD. This suggested that these traits are influenced by a common set of genetic variants.
Moreover, a significant proportion of this observed overlap appeared to be caused by variants that increased enjoyment of the effects of amphetamine but decreased the risk for both psychiatric diseases.
The researchers performed similar analyses for traits that were not expected to be related to amphetamine sensitivity, such as height, irritable bowel disease and Parkinson’s disease. In all of these cases they observed no more overlapping SNPs than would have been expected by chance alone.
“While this approach would not be a useful diagnostic test, we expect that people who like the effects of amphetamine would be slightly less likely to develop schizophrenia and ADHD,” Palmer said. “And people who did not like amphetamine, we would predict, are slightly more likely to develop these diseases.”
“What is particularly striking is that by examining people’s responses for just a few hours after taking a drug, we can identify an underlying genetic propensity that can manifest as a psychiatric disease over the course of a lifetime,” he adds.
These results provide unique genetic evidence for the role of dopamine in schizophrenia and ADHD. Schizophrenia is commonly treated using drugs that block dopamine signaling, while ADHD is treated using drugs, including d-amphetamine itself, that enhance dopamine signaling. Despite opposite treatments, amphetamine-liking SNPs reduced the risk for developing both diseases, suggesting that dopamine’s role is more complex than hypothesized.
The study also offers a new direction for the analysis of a wide range of similar genetic studies, particularly ones with smaller sample sizes. By analyzing the results of those studies for overlap with data from much larger genetic studies, promising genetic variants that would otherwise never stand out among the noise of hundreds of thousands of other random variants can be identified.
“Our approach offers a promising new direction for studying complex psychiatric behaviors using the whole-genome approach,” said co-author Harriet de Wit, PhD, professor of psychiatry and behavioral neuroscience at the University of Chicago.
The team plans to further study the SNPs identified in this study for their functional roles in amphetamine liking, schizophrenia and ADHD. In addition, Palmer hopes to explore genetic predispositions toward liking or disliking other therapeutic drugs and whether sensitivity to those drugs might also overlap with the diseases for which these drugs are used.
“When we use a drug treatment, we know exactly what systems have been perturbed,” Palmer said. “So when we see overlap for alleles that affect how you respond to drugs and a disease, we can hone in on what those alleles are doing biologically. This is instrumental for translating those results into new treatments and cures, which is the ultimate reason for performing genetic studies of disease.”
The study, “Genetic variation associated with euphorigenic effects of d-amphetamine is associated with diminished risk for schizophrenia and attention deficit hyperactivity disorder,” was supported by the National Institutes of Health. Additional authors include Amy B. Hart, Eric R. Gamazon, Barbara E. Engelhardt, Pamela Sklar, Anna K. Kähler, Christina M. Hultman, Patrick F. Sullivan, Benjamin M. Neale, Stephen V. Faraone, Psychiatric Genomics Consortium: ADHD Subgroup and Nancy J. Cox.
Kevin Jiang | newswise
Fish Oil-Diet Benefits May be Mediated by Gut Microbes
28.08.2015 | University of Gothenburg
Bio-fabrication of Artificial Blood Vessels with Laser Light
28.08.2015 | Fraunhofer-Institut für Lasertechnik ILT
A University of Oklahoma astrophysicist and his Chinese collaborator have found two supermassive black holes in Markarian 231, the nearest quasar to Earth, using observations from NASA's Hubble Space Telescope.
The discovery of two supermassive black holes--one larger one and a second, smaller one--are evidence of a binary black hole and suggests that supermassive...
A team of European researchers have developed a model to simulate the impact of tsunamis generated by earthquakes and applied it to the Eastern Mediterranean. The results show how tsunami waves could hit and inundate coastal areas in southern Italy and Greece. The study is published today (27 August) in Ocean Science, an open access journal of the European Geosciences Union (EGU).
Though not as frequent as in the Pacific and Indian oceans, tsunamis also occur in the Mediterranean, mainly due to earthquakes generated when the African...
In mountainous regions earthquakes often cause strong landslides, which can be exacerbated by heavy rain. However, after an initial increase, the frequency of these mass wasting events, often enormous and dangerous, declines, in fact independently of meteorological events and aftershocks.
These new findings are presented by a German-Franco-Japanese team of geoscientists in the current issue of the journal Geology, under the lead of the GFZ...
Bacteria do not cease to amaze us with their survival strategies. A research team from the University of Basel's Biozentrum has now discovered how bacteria enter a sleep mode using a so-called FIC toxin. In the current issue of “Cell Reports”, the scientists describe the mechanism of action and also explain why their discovery provides new insights into the evolution of pathogens.
For many poisons there are antidotes which neutralize their toxic effect. Toxin-antitoxin systems in bacteria work in a similar manner: As long as a cell...
It comes when called, bringing care utensils with it and recording how they are used: Fraunhofer IPA is developing an intelligent care cart that provides care staff with physical and informational support in their day-to-day work. The scientists at Fraunhofer IPA have now completed a first prototype. In doing so, they are continuing in their efforts to improve working conditions in the care sector and are developing solutions designed to address the challenges of demographic change.
Technical assistance systems can improve the difficult working conditions in residential nursing homes and hospitals by helping the staff in their work and...
20.08.2015 | Event News
20.08.2015 | Event News
19.08.2015 | Event News
28.08.2015 | Physics and Astronomy
28.08.2015 | Health and Medicine
28.08.2015 | Life Sciences