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Deng WQ, Belisario K, Munafò MR, MacKillop J. Longitudinal characterization of impulsivity phenotypes boosts signal for genomic correlates and heritability. Mol Psychiatry 2024:10.1038/s41380-024-02704-4. [PMID: 39181994 DOI: 10.1038/s41380-024-02704-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2024] [Revised: 08/14/2024] [Accepted: 08/16/2024] [Indexed: 08/27/2024]
Abstract
Genomic correlates of impulsivity have been identified in several genome-wide association studies (GWAS) using cross-sectional designs, but no studies have investigated the molecular genetic correlates of impulsivity phenotypes using longitudinally constructed traits. In 3860 unrelated European participants in the Avon Longitudinal Study of Parents and Children (ALSPAC), we constructed longitudinal phenotypes for delay discounting and impulsive personality traits (as measured by the UPPS-P impulsive behavior scales) via assessment at ages 24, 26, and 28. We conducted GWASs of impulsivity using both cross-sectional and longitudinal phenotypes, estimated heritability and their phenotypic and genetic correlations, and evaluated their association with recently-developed polygenic risk scores (PRSs) for the impulsivity indicators themselves and also related psychiatric conditions. Latent growth curve modeling revealed a stable intercept over time for all impulsivity phenotypes. High genetic correlation of cross-sectional measures over time suggested a stable genetic component for delay discounting (rg = 0.53-0.99) and sensation seeking (rg = 0.99). Heritability estimates of the stable longitudinal phenotypes substantively improved as compared to their cross-sectional counterparts, revealing a significant SNP-heritability for delay discounting (0.22; p = 0.03) and sensation seeking (0.35; p = 0.0007). Consistent with previous reports, GWAS and gene-based analyses revealed associations between specific longitudinal impulsivity indicators and CADM2 and NCAM1 genes. The PRSs for the impulsivity indicators and disorders related to self-regulation were also significantly associated with longitudinal impulsivity traits. Finally, we validated the associations between longitudinal impulsivity phenotypes and their PRSs in an independent 13-wave longitudinal study (n = 1019) and the benefit of longitudinal phenotypes in simulation studies. In this first longitudinal genetic study of impulsivity traits, the results revealed stable genomic correlates of delay discounting and sensation seeking over time and further validated the utility of recently-developed PRSs, both in relation to the observed traits and in connecting them to psychiatric disorders. More generally, these findings support using latent intercepts as novel longitudinal phenotypes to boost signal for heritability and genomic correlates of mechanisms contributing to psychiatric disease liability.
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Affiliation(s)
- Wei Q Deng
- Peter Boris Centre for Addictions Research, St. Joseph's Healthcare Hamilton, Hamilton, ON, Canada.
- Department of Psychiatry and Behavioural Neurosciences, McMaster University, Hamilton, ON, Canada.
| | - Kyla Belisario
- Peter Boris Centre for Addictions Research, St. Joseph's Healthcare Hamilton, Hamilton, ON, Canada
- Department of Psychiatry and Behavioural Neurosciences, McMaster University, Hamilton, ON, Canada
| | - Marcus R Munafò
- School of Psychological Science, University of Bristol, Bristol, UK
- MRC Integrative Epidemiology Unit, University of Bristol, Bristol, UK
| | - James MacKillop
- Peter Boris Centre for Addictions Research, St. Joseph's Healthcare Hamilton, Hamilton, ON, Canada.
- Department of Psychiatry and Behavioural Neurosciences, McMaster University, Hamilton, ON, Canada.
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2
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Impulse control differentiates Internet gaming disorder from non-disordered but heavy Internet gaming use: Evidence from multiple behavioral and multimodal neuroimaging data. COMPUTERS IN HUMAN BEHAVIOR 2022. [DOI: 10.1016/j.chb.2022.107184] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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3
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Keidel K, Rramani Q, Weber B, Murawski C, Ettinger U. Individual Differences in Intertemporal Choice. Front Psychol 2021; 12:643670. [PMID: 33935897 PMCID: PMC8085593 DOI: 10.3389/fpsyg.2021.643670] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Accepted: 03/08/2021] [Indexed: 11/23/2022] Open
Abstract
Intertemporal choice involves deciding between smaller, sooner and larger, later rewards. People tend to prefer smaller rewards that are available earlier to larger rewards available later, a phenomenon referred to as temporal or delay discounting. Despite its ubiquity in human and non-human animals, temporal discounting is subject to considerable individual differences. Here, we provide a critical narrative review of this literature and make suggestions for future work. We conclude that temporal discounting is associated with key socio-economic and health-related variables. Regarding personality, large-scale studies have found steeper temporal discounting to be associated with higher levels of self-reported impulsivity and extraversion; however, effect sizes are small. Temporal discounting correlates negatively with future-oriented cognitive styles and inhibitory control, again with small effect sizes. There are consistent associations between steeper temporal discounting and lower intelligence, with effect sizes exceeding those of personality or cognitive variables, although socio-demographic moderator variables may play a role. Neuroimaging evidence of brain structural and functional correlates is not yet consistent, neither with regard to areas nor directions of effects. Finally, following early candidate gene studies, recent Genome Wide Association Study (GWAS) approaches have revealed the molecular genetic architecture of temporal discounting to be more complex than initially thought. Overall, the study of individual differences in temporal discounting is a maturing field that has produced some replicable findings. Effect sizes are small-to-medium, necessitating future hypothesis-driven work that prioritizes large samples with adequate power calculations. More research is also needed regarding the neural origins of individual differences in temporal discounting as well as the mediating neural mechanisms of associations of temporal discounting with personality and cognitive variables.
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Affiliation(s)
- Kristof Keidel
- Department of Psychology, University of Bonn, Bonn, Germany
- Department of Finance, The University of Melbourne, Melbourne, VIC, Australia
| | - Qëndresa Rramani
- Center for Economics and Neuroscience, University of Bonn, Bonn, Germany
- Institute of Experimental Epileptology and Cognition Research, University of Bonn, Bonn, Germany
| | - Bernd Weber
- Center for Economics and Neuroscience, University of Bonn, Bonn, Germany
- Institute of Experimental Epileptology and Cognition Research, University of Bonn, Bonn, Germany
| | - Carsten Murawski
- Department of Finance, The University of Melbourne, Melbourne, VIC, Australia
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4
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Steep Discounting of Future Rewards as an Impulsivity Phenotype: A Concise Review. Curr Top Behav Neurosci 2020; 47:113-138. [PMID: 32236897 DOI: 10.1007/7854_2020_128] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
This chapter provides an overview over the behavioral economic index of impulsivity known as delay discounting. Specifically, delay discounting refers to an individual's preference for smaller immediate rewards over a larger delayed rewards. The more precipitously an individual discounts future rewards, the more impulsive they are considered to be. First, the chapter reviews the nature of delay discounting as a psychological process and juxtaposes it with nominally similar processes, including other facets of impulsivity. Second, the chapter reviews the links between delay discounting and numerous health behaviors, including addiction, attention deficit/hyperactivity disorder, and obesity. Third, the determinants of individual variation in delay discounting are discussed, including both genetic and environmental contributions. Finally, the chapter evaluates delay discounting as a potentially modifiable risk factor and the status of clinical interventions designed to reduce delay discounting to address deficits in self-control in a variety of maladaptive behaviors.
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5
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Kaminskaite M, Jokubka R, Janaviciute J, Lelyte I, Sinkariova L, Pranckeviciene A, Borutaite V, Bunevicius A. Epistatic effect of Ankyrin repeat and kinase domain containing 1 - Dopamine receptor D2 and catechol-o-methyltransferase single nucleotide polymorphisms on the risk for hazardous use of alcohol in Lithuanian population. Gene 2020; 765:145107. [PMID: 32889058 DOI: 10.1016/j.gene.2020.145107] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Revised: 08/24/2020] [Accepted: 08/27/2020] [Indexed: 10/23/2022]
Abstract
AIM The Lithuanian population has outstanding rates of alcohol consumption and alcohol related mortality. Alteration of brain dopaminergic system play a role in the risk for addiction disorders. We evaluated the association of one single nucleotide polymorphism rs1800497 in the Ankyrin Repeat and Kinase Domain Containing 1 - Dopamine Receptor D2 complex (ANKK1-DRD2) and a catechol-o-methyltransferase (COMT) rs4680 single nucleotide polymorphism with the risk for alcohol use disorder and impulsiveness in Lithuanian population. Both genetic polymorphisms are known to alter brain dopaminergic activity, thus we also investigated the possible interaction effect of these polymorphisms. METHODS The study included 329 participants recruited from the local community. Hazardous alcohol use was evaluated using the Alcohol Use Disorder Identification Test (AUDIT). Impulsiveness was measured using the Barratt Impulsiveness Scale - 11 (BIS-11). Between group differences of AUDIT and BIS-11 scores were examined stratified by genetic polymorphisms and their combinations. The independent effect of each polymorphism and their interaction for hazardous alcohol use were evaluated using adjusted logistic regression analyses. RESULTS The ANKK1-DRD2 rs1800497 polymorphism was associated with total AUDIT score, but not with the hazardous use of alcohol, as indicated by the AUDIT test cut-off of 8. The COMT rs4680 GG genotype was associated with the hazardous use of alcohol (adjusted OR = 2.094, p = 0.029), but this association was not statistically significant after adjustment for multiple comparisons. Presence of both COMT rs4680 and ANKK1-DRD2 rs1800497 GGxCT/TT polymorphisms was associated with significantly increased risk for hazardous use of alcohol (adjusted OR = 5.016, p = 0.005). The COMT rs4680 and ANKK1-DRD2 rs1800497 genetic polymorphisms, and their combination were not associated with impulsiveness. CONCLUSIONS Our study demonstrated that the interaction of COMT rs4680 and ANKK1-DRD2 rs1800497 genetic polymorphisms is associated with a hazardous use of alcohol.
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Affiliation(s)
- Migle Kaminskaite
- Neuroscience Institute, Lithuanian University of Health Sciences, Kaunas, Lithuania.
| | - Ramunas Jokubka
- Neuroscience Institute, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | | | - Inesa Lelyte
- Department of Psychology, Vytautas Magnus University, Kaunas, Lithuania
| | - Liuda Sinkariova
- Department of Psychology, Vytautas Magnus University, Kaunas, Lithuania
| | - Aiste Pranckeviciene
- Neuroscience Institute, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Vilmante Borutaite
- Neuroscience Institute, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Adomas Bunevicius
- Neuroscience Institute, Lithuanian University of Health Sciences, Kaunas, Lithuania
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6
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Paasche C, Weibel S, Wittmann M, Lalanne L. Time perception and impulsivity: A proposed relationship in addictive disorders. Neurosci Biobehav Rev 2019; 106:182-201. [DOI: 10.1016/j.neubiorev.2018.12.006] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2018] [Revised: 11/07/2018] [Accepted: 12/04/2018] [Indexed: 12/11/2022]
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7
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Human Self-Domestication and the Extended Evolutionary Synthesis of Addiction: How Humans Evolved a Unique Vulnerability. Neuroscience 2019; 419:100-107. [PMID: 31654715 DOI: 10.1016/j.neuroscience.2019.09.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Revised: 09/10/2019] [Accepted: 09/11/2019] [Indexed: 01/19/2023]
Abstract
Humans are more vulnerable to addiction in comparison to all other mammals, including nonhuman primates, yet there is a lack of research addressing this. This paper reviews the field of comparative addiction neuroscience, highlighting the significant inter-species variation in the mesocortical dopaminergic and other neuromodulatory systems involved in addiction. Artificial selection gives rise to significant changes in neuroanatomy, neurophysiology and behaviour as shown in certain rodent strains and other domesticated animals. These changes occur over a few generations, relatively short periods of time in evolutionary terms, and demonstrate how dynamic these neuromodulatory systems are in response to the environment. During the course of human evolution, traits crucial to our survival, expansion and domination (traits such as the ability to innovate, adapt to different environments and thrive in a civilization) have been positively selected for, yet also predispose humans to addiction. This is evident in our unique neurochemistry and receptor-drug activation potencies. Examples of these are provided as possible targets for precision medicine.
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Mitchell SH. Linking Delay Discounting and Substance Use Disorders: Genotypes and Phenotypes. Perspect Behav Sci 2019; 42:419-432. [PMID: 31976442 PMCID: PMC6768927 DOI: 10.1007/s40614-019-00218-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
Research supports the idea that "delay discounting," also known as temporal discounting, intertemporal choice, or impulsive choice, is a transdisease process with a strong connection to substance use disorders (SUDs) and other psychopathologies, like attention deficit hyperactivity disorder and depression. This article briefly reviews the evidence used to conclude that delay discounting is heritable and should be considered to be an endophenotype, as well as evidence of its behavioral and genetic associations with SUDs. It also discusses the limitations that should be considered when evaluating the strength of these associations. Finally, this article briefly describes research examining relationships among delay discounting and SUD-associated intermediate phenotypes to better understand the conceptual relationships underlying the links between SUDs and delay discounting, and identifies research gaps that should be addressed.
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Affiliation(s)
- Suzanne H. Mitchell
- Behavioral Neuroscience, Psychiatry, the Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239 USA
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9
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Acheson A, Vincent AS, Cohoon A, Lovallo WR. Early life adversity and increased delay discounting: Findings from the Family Health Patterns project. Exp Clin Psychopharmacol 2019; 27:153-159. [PMID: 30556730 PMCID: PMC6719544 DOI: 10.1037/pha0000241] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Increased discounting (devaluing) of delayed rewards is associated with nearly all types of substance use disorders (SUDs) and is also present in individuals with family histories of SUDs. Early life adversity (ELA) likely contributes to these findings as it is common in both individuals with SUDs and their children and is linked to increased delay discounting and other neurocognitive impairments in human and animal studies. Here we examined data from 1192 healthy young adults (average age 23.6 years old) with (SUDs+) and without (SUDs-) histories of SUDs and with (FH+) and without (FH-) family histories of SUDs. A 2-way ANOVA was conducted to examine the effects of SUDs (SUDs-, SUDs+) and FH (FH-, FH+) on delay discounting followed by an examination of the effects of adding ELA to the model. First, we replicated findings that SUDs+ and FH+ participants had increased rates of delay discounting. After taking ELA into account, the effect of SUDs and FH on delay discounting were both reduced but still significant. The association of ELA and delay discounting was similar in magnitude among both SUDs+ and SUDs- participants and FH+ and FH- participants; those with higher levels of ELA had increased delay discounting. Collectively, these findings indicate that increased ELA is closely associated with the increased delay discounting seen in SUDs+ and FH+ individuals and suggests ELA may be contributing to the increased delay discounting seen in these populations. (PsycINFO Database Record (c) 2019 APA, all rights reserved).
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Affiliation(s)
- Ashley Acheson
- Psychiatry and Behavioral Science, University of Arkansas for Medical Sciences Little Rock, AR,, Psychiatry and Behavioral Sciences, University of Arkansas for Medical Sciences, 4301 W. Markham St., Little Rock, AR 72205, Phone number: 501-526-8437
| | - Andrea S. Vincent
- Cognitive Science Research Center, University of Oklahoma, Norman, OK
| | - Andrew Cohoon
- Behavioral Sciences Laboratories, Veterans Affairs Medical Center, Oklahoma City, OK
| | - William R. Lovallo
- Behavioral Sciences Laboratories, Veterans Affairs Medical Center, Oklahoma City, OK
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10
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MacKillop J, Gray JC, Weafer J, Sanchez-Roige S, Palmer AA, de Wit H. Genetic influences on delayed reward discounting: A genome-wide prioritized subset approach. Exp Clin Psychopharmacol 2019; 27:29-37. [PMID: 30265060 PMCID: PMC6908809 DOI: 10.1037/pha0000227] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Delayed reward discounting (DRD) is a behavioral economic measure of impulsivity that has been consistently associated with addiction. It has also been identified as a promising addiction endophenotype, linking specific sources of genetic variation to individual risk. A challenge in the studies to date is that levels of DRD are often confounded with prior drug use, and previous studies have also had limited genomic scope. The current investigation sought to address these issues by studying DRD in healthy young adults with low levels of substance use (N = 986; 62% female, 100% European ancestry) and investigating genetic variation genome-wide. The genome-wide approach used a prioritized subset design, organizing the tests into theoretically and empirically informed categories and apportioning power accordingly. Three subsets were used: (a) a priori loci implicated by previous studies; (b) high-value addiction (HVA) markers from the recently developed SmokeScreen array; and (c) an atheoretical genome-wide scan. Among a priori loci, a nominally significant association was present between DRD and rs521674 in ADRA2A. No significant HVA loci were detected. One statistically significant genome-wide association was detected (rs13395777, p = 2.8 × 10-8), albeit in an intergenic region of unknown function. These findings are generally not supportive of the previous candidate gene studies and suggest that DRD has a complex genetic architecture that will require considerably larger samples to identify genetic associations more definitively. (PsycINFO Database Record (c) 2019 APA, all rights reserved).
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Affiliation(s)
- James MacKillop
- Peter Boris Centre for Addictions Research, McMaster University/St. Joseph’s Healthcare Hamilton, Hamilton, ON L8P 3R2, Canada,Homewood Research Institute, Homewood Health Centre, Guelph, ON N1E 4J3 Canada
| | - Joshua C. Gray
- Department of Psychology, University of Georgia Athens, GA 30602, USA,Department of Psychiatry and Human Behavior, Brown University, Providence, RI 02912
| | - Jessica Weafer
- Department of Psychiatry and Behavioral Neuroscience, University of Chicago, Chicago, IL 60637, USA
| | - Sandra Sanchez-Roige
- Department of Psychiatry, University of California, San Diego, San Diego, CA 92093, USA
| | - Abraham A. Palmer
- Department of Psychiatry, University of California, San Diego, San Diego, CA 92093, USA,Institute for Genomic Medicine, University of California San Diego, La Jolla, CA 92103, USA
| | - Harriet de Wit
- Department of Psychiatry and Behavioral Neuroscience, University of Chicago, Chicago, IL 60637, USA
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11
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Kozak K, Lucatch AM, Lowe DJE, Balodis IM, MacKillop J, George TP. The neurobiology of impulsivity and substance use disorders: implications for treatment. Ann N Y Acad Sci 2018; 1451:71-91. [PMID: 30291624 DOI: 10.1111/nyas.13977] [Citation(s) in RCA: 94] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Revised: 09/11/2018] [Accepted: 09/13/2018] [Indexed: 12/20/2022]
Abstract
Impulsivity is strongly associated with substance use disorders (SUDs). Our review discusses impulsivity as an underlying vulnerability marker for SUDs, and treatment of co-occurring impulsivity in SUDs. Three factors should be considered for the complex relationship between impulsivity and a SUD: (1) the trait effect of impulsivity, centering on decreased cognitive and response inhibition, (2) the state effect resulting from either acute or chronic substance use on brain structure and function, and (3) the genetic and environmental factors (e.g., age and sex) may influence impulsive behavior associated with SUDs. Both subjective and objective measures are used to assess impulsivity. Together, treatment developments (pharmacological, behavioral, and neurophysiological) should consider these clinically relevant dimensions assessed by a variety of measures, which have implications for treatment matching in individuals with SUD. Despite its heterogeneity, impulsivity is a marker associated with SUDs and may be understood as an imbalance of bottom-up and top-down neural systems. Further investigation of these relationships may lead to more effective SUD treatments.
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Affiliation(s)
- Karolina Kozak
- Addictions Division, Centre for Addiction and Mental Health (CAMH), University of Toronto, Toronto, Ontario, Canada.,Division of Brain and Therapeutics, Department of Psychiatry, University of Toronto, Toronto, Ontario, Canada.,Institute of Medical Sciences, University of Toronto, Toronto, Ontario, Canada
| | - Aliya M Lucatch
- Addictions Division, Centre for Addiction and Mental Health (CAMH), University of Toronto, Toronto, Ontario, Canada
| | - Darby J E Lowe
- Addictions Division, Centre for Addiction and Mental Health (CAMH), University of Toronto, Toronto, Ontario, Canada
| | - Iris M Balodis
- Department of Psychiatry and Behavioural Neurosciences, McMaster University, Hamilton, Ontario, Canada
| | - James MacKillop
- Department of Psychiatry and Behavioural Neurosciences, McMaster University, Hamilton, Ontario, Canada
| | - Tony P George
- Addictions Division, Centre for Addiction and Mental Health (CAMH), University of Toronto, Toronto, Ontario, Canada.,Division of Brain and Therapeutics, Department of Psychiatry, University of Toronto, Toronto, Ontario, Canada.,Institute of Medical Sciences, University of Toronto, Toronto, Ontario, Canada
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12
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Guttman Z, Moeller SJ, London ED. Neural underpinnings of maladaptive decision-making in addictions. Pharmacol Biochem Behav 2018; 164:84-98. [PMID: 28666893 PMCID: PMC5745312 DOI: 10.1016/j.pbb.2017.06.014] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Revised: 06/07/2017] [Accepted: 06/26/2017] [Indexed: 01/22/2023]
Affiliation(s)
- Zoe Guttman
- Neuroscience Interdepartmental Program, University of California Los Angeles, Los Angeles, CA 90095, United States
| | - Scott J Moeller
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY 10029, United States; Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY 10029, United States
| | - Edythe D London
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY 10029, United States; Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095, United States; Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095, United States; Brain Research Institute, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095, United States.
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13
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Calvey T. The extended evolutionary synthesis and addiction: the price we pay for adaptability. PROGRESS IN BRAIN RESEARCH 2017; 235:1-18. [PMID: 29054284 DOI: 10.1016/bs.pbr.2017.07.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Humans are more likely to become addicted and to stay addicted than are other animals. This chapter is a neurobiological and molecular review of addiction and the cooccurring traits and psychiatric disorders from the perspective of the Extended Evolutionary Synthesis (EES). Addiction is an example of pleiotropy as many common haplotypes that are associated with individual differences in vulnerability to substance dependence express a variety of important brain-based phenotypes such as neuroadaptive processes. The neurochemical mechanisms of addiction are shared with behavioral flexibility and the ability to innovate, which are hallmark features of our species. The dopaminergic system provides a link between addiction and the cooccurring traits and psychiatric disorders evident in the shared genetic profile. A hypofunctioning dopaminergic system is also a common characteristic feature of addiction and the cooccurring traits and psychiatric disorders. Epigenetics allows for environmental factors to create lasting and heritable phenotypic changes enabling rapid adaptation to an environment. Addiction "high-jacks" this system as well as the neurochemical mechanisms that control flexibility and innovation and is, thus, the price we pay for adaptability.
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Affiliation(s)
- Tanya Calvey
- School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
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14
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Jackson JNS, MacKillop J. Attention-Deficit/Hyperactivity Disorder and Monetary Delay Discounting: A Meta-Analysis of Case-Control Studies. BIOLOGICAL PSYCHIATRY. COGNITIVE NEUROSCIENCE AND NEUROIMAGING 2016; 1:316-325. [PMID: 27722208 PMCID: PMC5049699 DOI: 10.1016/j.bpsc.2016.01.007] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
BACKGROUND A growing number of studies have investigated delay discounting, a behavioral economic index of impulsivity, and its relevance to attention deficit hyperactivity disorder (ADHD), but with mixed findings. The current meta-analysis synthesizes the literature on the relationship between monetary delay discounting and ADHD in studies using case-control designs. Specifically, the objectives were: 1) to characterize the aggregated differences in monetary delay discounting between individuals with ADHD (cases) and controls in studies using categorical case-control designs; 2) to examine potential differences based on sample age (<18 vs. >18), reward outcome (real vs. hypothetical), and prevalence of conduct disorder and oppositional defiant disorder in the sample; and 3) to evaluate potential small-study (publication) bias in the literature. METHODS From 567 candidate articles, 21 independent investigations yielded 25 case-control comparisons (total N=3,913). Random effects meta-analysis was conducted using Cohen's d as the common effect size. Publication bias was evaluated using fail-safe N, Begg-Mazumdar and Egger tests, and metaregression of publication year and effect size. RESULTS Across studies, a statistically significant difference of medium magnitude effect size was present for the case-control comparisons (d=0.43; p < 10-15). No significant differences based on sample age, reward outcome, or comorbid status was detected. Minimal heterogeneity and evidence of publication bias was present. CONCLUSIONS These findings provide robust evidence that delay discounting is significantly elevated among individuals with ADHD compared to controls. Gaps in the literature and the importance of characterizing the neural and genetic bases of this relationship are discussed.
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Affiliation(s)
- Jacob N S Jackson
- Peter Boris Centre for Addictions Research, McMaster University/St. Joseph's Healthcare Hamilton, Hamilton, Ontario, Canada
| | - James MacKillop
- Peter Boris Centre for Addictions Research, McMaster University/St. Joseph's Healthcare Hamilton, Hamilton, Ontario, Canada; Homewood Research Institute, Homewood Health Centre, Guelph, Ontario, Canada
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15
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MacKillop J. The Behavioral Economics and Neuroeconomics of Alcohol Use Disorders. Alcohol Clin Exp Res 2016; 40:672-85. [PMID: 26993151 PMCID: PMC4846981 DOI: 10.1111/acer.13004] [Citation(s) in RCA: 105] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2015] [Accepted: 01/04/2016] [Indexed: 12/13/2022]
Abstract
BACKGROUND Behavioral economics and neuroeconomics bring together perspectives and methods from psychology, economics, and cognitive neuroscience to understand decision making and choice behavior. Extending an operant behavioral theoretical framework, these perspectives have increasingly been applied to understand the alcohol use disorders (AUDs), and this review surveys the theory, methods, and findings from this approach. The focus is on 3 key behavioral economic concepts: delay discounting (i.e., preferences for smaller immediate rewards relative to larger delayed rewards), alcohol demand (i.e., alcohol's reinforcing value), and proportionate alcohol-related reinforcement (i.e., relative amount of psychosocial reinforcement associated with alcohol use). FINDINGS Delay discounting has been linked to AUDs in both cross-sectional and longitudinal studies and has been investigated cross-sectionally using neuroimaging. Alcohol demand and proportionate alcohol-related reinforcement have both been robustly associated with drinking and alcohol misuse cross-sectionally, but not over time. Both have also been found to predict treatment response to brief interventions. Alcohol demand has also been used to enhance the measurement of acute motivation for alcohol in laboratory studies. Interventions that focus on reducing the value of alcohol by increasing alternative reinforcement and response cost have been found to be efficacious, albeit in relatively small numbers of randomized controlled trials (RCTs). Mediators and moderators of response to these interventions have not been extensively investigated. FUTURE DIRECTIONS The application of behavioral economics and neuroeconomics to AUDs has given rise to an extensive body of empirical work, although significant gaps in knowledge remain. In particular, there is a need for more longitudinal investigations to clarify the etiological roles of these behavioral economic processes, especially alcohol demand and proportionate alcohol reinforcement. Additional RCTs are needed to extend and generalize the findings for reinforcement-based interventions and to investigate mediators and moderators of treatment success for optimization. Applying neuroeconomics to AUDs remains at an early stage and has been primarily descriptive to date, but has high potential for important translational insights into the future. The same is true for using these behavioral economic indicators to understand genetic influences on AUDs.
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Affiliation(s)
- James MacKillop
- Peter Boris Centre for Addictions Research, Department of Psychiatry and Behavioural Neurosciences, McMaster University/St Joseph’s Healthcare Hamilton
- Homewood Research Institute, Homewood Health Centre
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Gray JC, MacKillop J. Impulsive delayed reward discounting as a genetically-influenced target for drug abuse prevention: a critical evaluation. Front Psychol 2015; 6:1104. [PMID: 26388788 PMCID: PMC4554956 DOI: 10.3389/fpsyg.2015.01104] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Accepted: 07/17/2015] [Indexed: 12/22/2022] Open
Abstract
This review evaluates the viability of delayed reward discounting (DRD), an index of how much an individual devalues a future reward based on its delay in time, for genetically-informed drug abuse prevention. A review of the literature suggests that impulsive DRD is robustly associated with drug addiction and meets most of the criteria for being an endophenotype, albeit with mixed findings for specific molecular genetic influences. Several modes of experimental manipulation have been demonstrated to reduce DRD acutely. These include behavioral strategies, such as mindfulness, reward bundling, and episodic future thinking; pharmacological interventions, including noradrenergic agonists, adrenergic agonists, and multiple monoamine agonists; and neuromodulatory interventions, such as transcranial magnetic stimulation and transcranial direct current stimulation. However, the generalization of these interventions to positive clinical outcomes remains unclear and no studies to date have examined interventions on DRD in the context of prevention. Collectively, these findings suggest it would be premature to target DRD for genetically-informed prevention. Indeed, given the evidence of environmental contributions to impulsive DRD, whether genetically-informed secondary prevention would ever be warranted is debatable. Progress in identifying polymorphisms associated with DRD profiles could further clarify the underlying biological systems for pharmacological and neuromodulatory interventions, and, as a qualitatively different risk factor from existing prevention programs, impulsive DRD is worthy of investigation at a more general level as a novel and promising drug abuse prevention target.
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Affiliation(s)
- Joshua C Gray
- Department of Psychology, University of Georgia , Athens, GA, USA
| | - James MacKillop
- Department of Psychology, University of Georgia , Athens, GA, USA ; Peter Boris Centre for Addictions Research, McMaster University/St. Joseph's Healthcare Hamilton , Hamilton, ON, Canada
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