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Exam 1 MIDTERM Psyc 338 articles.docx

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McGill University
PSYC 338
Robert Pihl

Epidemiology of substance use disorder Merikangas & McClair Aim of the article:  Overview of most recent data on the epidemiology of substance use and dependence  Methods and findings on the genetic epidemiology Epidemiologists are interested in: Epidemiology: the study of rates, distribution and determinants of disease in human population  The rates, distribution and determinants of diseases in human population  Types of illnesses in populations and factors that influence the distribution of certain illnesses  Interaction among host, agent and environment (= the epidemiological triangle)  Identifying the etiology of disease and prevention Descriptive epidemiology: rates and distribution in a given population Analytic epidemiology: the determinants of disease in certain groups Studies of substance use focus on polysubstance users–they are more at risk for developing substance use disorder (SUD) = when substance use becomes more severe and leads to impairment of living conditions and negative life consequences.  More studies try to reveal patterns of substance use (what is used, how much, who becomes at risk etc.). Prevalence rates of Substance use Disorder in the US: Adults:  Generally higher prevalence for alcohol dependence than for drugs abuse and dependence  Lifetime rates exceed 12 months rates for drug abuse in NESARC  The NESARC (National Epidemiological Survey On Alcohol and Related Conditions) and the NCSR study (National Comorbidity Survey Replication) Youth:  More research is needed! Why important? Identification of early onset SUD, psychological disorders, negative life consequences, which is related to comorbid and continued abuse.  Abuse>dependance Abuse versus dependence:  Rates for abuse of alcohol and drugs are 4 times higher than the rates for alcohol and drug dependence Lifetime prevalence of SUD according to NCSA (The National Comorbidity Survey Adolescent Supplement.): 6.5% for alcohol / 8.9% for illicit drug  Resonates with the finding that ages 13 to 18 are a key period of development of SUD. Age and sex trends:  Males have nearly double the rates of both alcohol and drugs SUD than females (Same pattern for adults but mostly with alcohol)  Though females have higher rates in e.g. cocaine dependence and psychotherapeutic drugs  Alcohol use disorder was found to be more persistent in women than in men  18-25 years old use of alcohol and illicit drugs begins  Reduces after age 26  NSDUH (National Survey on Drug use and Health), 2011  Progression to use substances regularly is also based on individual and familial factors Genetic epidemiology:  Close to epidemiology and human genetics but different  Interested in the joint effects of genes and environment and the underlying biology of diseases  Stresses on the importance of genes (and how genes work together with the environment to produce certain diseases) whereas epidemiological studies are more concerned with identifying environmental disease risk factors Variables: Control for the environment or for the genetic background  DV (Dependent Variable)  IV (Independent variable) 1. Control for the genetic background (Dependent Variable) while letting the environment (Independent Variable) vary  e.g. imigrant studies, separated twins 2. Control for the environment (DV) while letting the genetic background (IV) vary  e.g. siblings, adoptees, non-biological siblings Challenges in the field of genetic epidemiology:  Problem with the DSMIV: Phenotypic definitions, abuse disorders versus dependence disorders.  The right degree of overlapping between the different substance use disorders in the DSM.  Distinct disorders or a continuum, a graduation of a single disorder?  Change in the DSMIV: Disorder will be characterized by severity rather than distinct abuse of dependence disorders. Comorbidity with other mental disorders:  Shared vulnerability between substance disorder and nearly all classes of psychiatric disorders – Same genetic etiology?  Substance use disorders and mental disorders coaggregate among families (= Relative of substance user disorders are at increased risk of developing both substance abuse and “mental disorders”)  When comorbid (SUD and mental disorder) most studies have found that SUD is subsequent to mental disorders. Family Studies:  SUD aggregates in families (most studies on alcohol)  8 times higher risk to develop drug disorder among relatives of those with drug disorders compared with relatives of psychiatric and unaffected controls  Some studies report specificity for the substance use (same illicit drug as the parent) Twin studies:  When use of drugs becomes serious (SUD) genes play an important role, while the environment plays a bigger role in the initial exposure to the drug  Heritability varies for the different drugs. o Median: 53-55 %. (male and female respectively)  Unique environmental factors play a much greater role than shared environment  Specificity for familial aggregates of certain substances (e.g. opiates, cannabis, alcohol)  Twin and family studies points to common genetic factors underlying substance use in general AND components that are unique for certain drugs Adoption studies: The studies suggest two major genetic pathways in the ability to develop drug abuse 1. Substance abuse in the biological parent 2. Aggressiveness and anti-social personality disorder in the biological parent Migration studies:  Points to certain environmental risk factors.  Study using Puerto Rican immigrants o Immigrant adolescents showed higher rates alcohol use and less drug use compared to the main land Puerto Rican adolescent–more drugs, less alcohol Genetic and Familial Environmental Influences on the Risk for Drug Abuse Kendler et al. Goal of the study:  Examine the influence of genetic and familial environmental factors on drug abuse  Much effort into understanding the role of familial environmental factors on drug abuse  They have shown that low SES, parental divorce & death, parental DA, criminal history and psychology as well as disrupted family functioning all correlate with DA  Studies typically employ intact families where genes might be a confounding variable  By using an adoption study, Kendler et al. can separate the two. Sample:  Adopted  Available information on both adoptive parents  Available information about at least one biological parent Methods:  9 sources to gather their information o Swedish Hospital Discharge Register (all hospitalizations due to drug use) o Swedish Prescribed Drug Register (all prescriptions) o Swedish Mortality Register (causes of death) o National Census (education, marital status) o Total Population Register (annual data of education and marital status) o Multi-Generation Register (family relationships) o Outpatient Care Register (outpatient clinics) o Primary Health Care Register (outpatient care data on diagnoses and time) o Swedish Crime Register (convictions including those for drug abuse)  Only looked at individuals adopted by non-biologically related parents  Did not include alcohol-related problems  Used familial alcohol problems as risk factor Genetic Risk score: Related to biological parent/sibling (include 1/2 sibling  1/2 score of full sibling). At least one parent had to be identified according to the criteria:  Drug abuse  Hospitalization attributed to alcoholism  Hospitalizations for psychiatric illness  Criminality Education was used to estimate SES Divorce among biological mother and age of mother at birth were considered Environmental Risk score: Factors reflecting the dysfunction in the family of origin increase the risk of subsequent use and abuse of illicit substances. Variables in adoptive parents  Drug abuse  Hospitalization attributed to alcoholism  Criminality  Divorce  Hospitalization for psychiatric illness  Death Education was used to estimate SES Age of adoptive mother at time of adoption Environmental Risk score: factors reflecting general family dysfunction and possible exposure for the siblings in the household to deviant peer networks. Variables in adoptive siblings  Drug abuse  Hospitalization attributed to alcoholism  Hospitalization for psychiatric illness  Criminality Results Notably:  Adoptees have higher rates of substance abuse than non-adoptees (4.5% vs 2.9%) Table 2:  Rates of DA, hospitalization for psychiatric illness and alcoholism, criminality, low education and divorce: biological parents/siblings > adoptive parents/siblings Table 3  If biological parent(s) have drug abuse problems, the risk for their offspring is significantly increased (from 4.2% for neither, 8.2% for one, and 11.9% for both)  Either or both adoptive parents with drug abuse, no significant effect  Adoptive siblings of a child with drug abuse problem have increased risk of drug abuse (3.2% vs. 6.2%) Table 4 Adoptive siblings have higher correlations than adoptive parents  Notable Parents: convictions, maternal divorce, death  Notable Siblings: drug abuse Adoptive siblings have higher correlations than biological siblings Biological parents have high correlations with drug abuse, psychiatric disease, alcoholism and convictions Table 5 Genetic risk score (1.12) + Environmental risk score (1.09) + Sex (1.44 MvsF)Correlate well with DA  Not shown: Sex does not affect environmental risk, but males are more sensitive to genetic risk factors Table 6 & figure  Adverse environment affects those with high genetic risk more than those with low genetic risk for DA 5 Noteworthy Results: 1. Replicated results from other studies that showed strong contribution of genetic factors on drug abuse 2. Greater risk for drug abuse in offspring of fathers with drug abuse (vs. Mothers)
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