Extraversion. Interaction between D2 dopamine receptor polymorphisms and parental alcoholism.

Both molecular genetic factors (the D2 dopamine receptor (DRD2) and the D4 dopamine receptor (DRD4) polymorphisms) and environmental influences of living in an alcoholic or nonalcoholic home on the personality traits of Extraversion and Neuroticism were assessed in drug-naive, young adolescent boys. There were no significant main effects of genetic or environmental factors on either Neuroticism or Extraversion as measured by the Junior Eysenck Personality Inventory (JEPI). However, a significant interaction between DRD2 (but not DRD4) alleles and environmental variables was observed on Extraversion. Specifically, children with the minor alleles of the DRD2 gene showed a significantly greater Extraversion score when living in an alcoholic than in a nonalcoholic home. In contrast, children with the major alleles of the DRD2 gene showed a trend in the opposite direction. Although the results are preliminary and pending replication, they nevertheless provide the first report of a specific gene-environment interaction involving a human personality trait.

D2 and D4 dopamine receptor polymorphisms and personality.

The relationship of various dimensions of temperament, measured by the Tridimensional Personality Questionnaire (TPQ), to polymorphisms of the D2 dopamine receptor (DRD2) and D4 dopamine receptor (DRD4) genes was determined in 119 healthy Caucasian boys who had not yet begun to consume alcohol and other drugs of abuse. Total Novelty Seeking score of the TPQ was significantly higher in boys having, in common, all three minor (A1, B1, and Intron 6 1) alleles of the DRD2 compared to boys without any of these alleles. Boys with the DRD4 7 repeat (7R) allele also had a significantly higher Novelty Seeking score than those without this allele. However, the greatest difference in Novelty Seeking score was found when boys having all three minor DRD2 alleles and the DRD4 7R allele were contrasted to those without any of these alleles. Neither the DRD2 nor the DRD4 polymorphisms differentiated total Harm Avoidance score. Whereas subjects having all three minor DRD2 alleles had a significantly higher Reward Dependence 2 (Persistence) score than subjects without any of these alleles, no significant difference in this personality score was found between subjects with and without the DRD4 7R allele. In conclusion, DRD2 and DRD4 polymorphisms individually associate with Novelty Seeking behavior. However, the combined DRD2 and DRD4 polymorphisms contribute more markedly to this behavior than when these two gene polymorphisms are individually considered.

Neuropsychological functioning in sons of active alcoholic, recovering alcoholic, and social drinking fathers.

Sons of active alcoholic, recovering alcoholic, and social drinking fathers were administered neuropsychological tests to assess whether they differ in their cognitive functioning. Multivariate analyses of variance showed that sons of active alcoholic sons perform significantly worse on visuospatial, memory, and attentional tasks as well as general intellectual functioning than sons of social drinking fathers. The sons of recovering alcoholic fathers showed no significant difference from social drinking fathers in their cognitive functioning. These results suggest that the clinical type of the alcoholic father (i.e., inability to abstain, more severe alcoholic vs. ability to abstain, less severe alcoholic) may be an important factor that determines whether offspring of alcoholics have neuropsychological deficits.

Neuropsychological differences between sons of active alcoholic and non-alcoholic fathers.

Ten- to fourteen-year-old sons of active alcoholic fathers (n = 59) with a positive family history of alcoholism (AFH+) and sons of social drinker fathers (n = 58) with a negative family history of alcoholism (NFH-) were administered a battery of neuropsychological tasks. Areas of cognitive function which were assessed were memory, visuospatial and attentional abilities and, in addition, motor skills and general intellectual functioning. MANOVAs conducted on these measures showed that sons of active alcoholic fathers' performance on the more difficult visuospatial and memory tasks as well as on an attentional test was reduced relative to sons of non-alcoholic fathers.

Prolonged P300 latency in children with the D2 dopamine receptor A1 allele.

Previous studies have indicated the presence of a hereditary component in the generation of the P300, or P3, a late positive component of the event-related potential. Moreover, the dopaminergic system has been implicated in the P3. In the present study, 98 healthy Caucasian boys, mean age of 12.5 years and of above-average intelligence, were studied. The sample was composed of 32 sons of active alcoholic (SAA) fathers, 36 sons of recovering alcoholic (SRA) fathers, and 30 sons of social drinker (SSD) fathers, with none of them having yet begun to consume alcohol or other drugs. TaqI A D2 dopamine receptor alleles (A1 and A2) were determined. A significant difference in the frequency of the A1 allele was found among these three groups of boys, with the SAA group having the highest A1 allele frequency (.313), followed by the SRA (.139) and the SSD (.133) groups. The relationship of the A1 and A2 alleles to P3 amplitude and latency was also determined. The results showed no significant difference in P3 amplitude between boys with the A1 and A2 allele. However, P3 latency was significantly longer in the total sample of boys with the A1 allele compared with those carrying the A2 allele. These findings suggest that polymorphism of the D2 dopamine receptor gene is an important determinant of P3 latency.

Allelic association of the D2 dopamine receptor gene with cocaine dependence.

The objective of the present study was to examine allelic prevalence of the D2 dopamine receptor (DRD2) gene in male cocaine-dependent (CD) Caucasian (non-Hispanic) subjects and to determine the relationship of DRD2 alleles to family history and selected behavioral measures. The prevalence of the A1 allele in CD subjects (n = 53) was 50.9%. It was significantly higher than either the 16.0% prevalence (P < 10(-4)) in non-substance abusing controls (n = 100) or the 30.9% prevalence (P < 10(-2)) in population controls (n = 265) wherein substance abusers were not excluded. Similarly, a significantly higher prevalence (P < 10(-2)) of the B1 allele was found in CD subjects (n = 52) compared with non-substance abusing controls (n = 53); 38.5% vs. 13.2%. Logistic regression analysis of CD subjects identified potent routes of cocaine use and the interaction of early deviant behaviors and parental alcoholism as significant risk factors associated with the A1 allele. The cumulative number of these three risk factors in CD subjects was positively and significantly (P < 10(-3)) related to A1 allelic prevalence. The data showing a strong association of the minor alleles (A1 and B1) of the DRD2 with cocaine dependence suggest that a gene, located on the q22-q23 region of chromosome 11, confers susceptibility to this drug disorder.

Creativity in alcoholic and nonalcoholic families.

A battery of creativity tests was administered to 56 families (fathers, mothers, and their pubescent sons) representing three groups. Group A+ was comprised of recovering alcoholic fathers with a family history of alcoholism (n = 19). Group NA+ consisted of nonalcoholic fathers with a family history of alcoholism (n = 18). Group NA- was composed of nonalcoholic fathers without a family history of alcoholism (n = 19). None of the mothers or sons in these three family groups was alcoholic. All subjects completed the Creativity Personality Scale, the four Origence/Intellectence scales from the Adjective Check List, and the How Do You Think Test. Moreover, fathers and sons received two divergent thinking tests, and mothers rated their sons using a special scale from the Adjective Check List. Results indicate that alcoholic fathers and their sons had generally lower creativity scores than fathers and sons of the other two groups. The mothers did not differ. Moreover, there were significant correlations between fathers' and sons' creativity scores and significant interactions, indicating that the father-son relationships differed among the three groups. The implications of these results are discussed.

Genetic predisposition in alcoholism: association of the D2 dopamine receptor TaqI B1 RFLP with severe alcoholics.

Previous studies have shown an association of the 3' Taq1 A1 allele of the D2 dopamine receptor (DRD2) gene with severe alcoholism. The recent demonstration of a new polymorphism located closer to the regulatory regions of this gene, permits an associational analysis of these 5' Taq1 B alleles with alcoholism and a comparison with the 3' Taq1 A alleles. Restriction fragment length polymorphism methodology was used to analyze a total of 133 blood samples of nonalcoholics, less severe alcoholics, and severe alcoholics. In white subjects (n = 115), no significant difference in the prevalence of the B1 allele is found between nonalcoholics (n = 30) and less severe alcoholics (n = 36). However, the prevalence of this allele is significantly higher in severe alcoholics (n = 49) when compared to either nonalcoholics (p = 0.008) or less severe alcoholics (p = 0.005). When Taq1 B and Taq1 A alleles of the DRD2 gene are compared in whites, the prevalence of the A1 allele is significantly higher than the B1 allele only in the severe alcoholic group. In conclusion, alleles in both the 5' and 3' region of the DRD2 gene associate with severe alcoholism. This suggests that the DRD2 gene may have an etiological role in some severe alcoholics.

Association of the A1 allele of the D2 dopamine receptor gene with severe alcoholism.

In a blinded study, 159 subjects composed of nonalcoholics (N = 43), less severe alcoholics (N = 44), severe alcoholics (N = 52) and young children of alcoholics (CoAs, N = 20) were studied for their allelic association with the D2 dopamine receptor (D2DR) gene utilizing peripheral lymphocytes as the DNA source. The combined alcoholic group compared to the nonalcoholic group showed a significantly greater association with the A1 allele of the D2DR gene. Furthermore, an even more robust association was found when severe alcoholics were compared to nonalcoholics. CoAs also showed a significantly greater association with the A1 allele than nonalcoholics but not when compared to alcoholics. Analysis of risk of alcoholism severity suggests that it comprises of two independent components: family history of alcoholism and presence of the A1 allele. Genotype and allelic frequency of the D2DR gene were also analyzed with respect to race. A higher percentage of blacks compared to whites had the A1/A1 genotype, and A1 allelic frequency in the total sample of blacks was significantly greater than in the total sample of whites. Moreover, frequency of the A1 allele was significantly greater in severe alcoholics compared to nonalcoholics in both whites and blacks. However, due to the small sample size of blacks, these racial differences need to be further studied. This study, of the largest sample of alcoholics to date, strongly affirms association of severe alcoholism with the A1 allele of the D2DR gene.