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fpsyg-08-01361 August 7, 2017 Time: 15:7 # 4
Rozenblat et al. 5-HTTLPR and Disordered Eating was coded as per the di-allelic model into s-present (s/s or s/l genotype) or s-absent (l/l genotype) groups, as the s-allele is believed to operate in a genetically dominant manner ( Lesch
et al., 1996 ). Potential Confounding Factors Age, height, and weight were self-reported at age 15–16, with the latter two figures used to calculate participant BMI. SES status was measured according to maternal and paternal education and occupation as reported by parents in the first survey in 1983. Data Analysis The main and interaction effects of 5-HTTLPR and the two psychological stress exposures (depression and emotional control), as well as the three social stress exposures (sexual abuse, mild-to-moderate parental punishment, and severe parental physical punishment), were assessed using separate linear regression models. Outcome variables were Drive for Thinness and Bulimia scores. G×E models were adjusted for sex and BMI, as per Keller (2014) , by including all the covariate × gene and covariate × environment interaction terms in the regression models. Prior to analyses, missing data (23.5%) for the BMI variable were imputed using multiple imputation in IBM SPSS Version 21, with no systematic patterns of missingness observed. A total of 10 tests were conducted with p-values adjusted accordingly (adjusted p-value = 0.05/10, corrected p = 0.005), to correct for multiple-testing, a frequent limitation of genetic association studies ( Munafò and Flint, 2009 ). Standardized effect sizes are reported. RESULTS
5-HTTLPR genotype distribution (l/l = 197, s/l = 341, and s/s = 112) for the overall sample met the Hardy–Weinberg Equilibrium, χ 2 = 2.96,
df = 1, p > 0.05. 5-HTTLPR genotype TABLE 1 | Sociodemographic details of participants included in the present sample. Full sample Females Males
N N % N % N % Sex
650 Males
312 49.8
Females 338
50.2 SES Quartile 632 Highest
231 36.6
116 36.6
115 36.5
Medium-High 197
31.2 103
32.5 94 29.8 Medium-Low 129
20.4 59 18.6 70 22.2
Lowest 75 11.9 39 12.3
36 11.4
Parent marital status 645
Married/De facto 538
83.4 264
81.5 274
85.4 Separated/Divorced 73 11.3
42 13.0
31 9.7
Single/Widowed 22 3.4 10 3.1
12 3.7
Remarried 12 1.8 8 2.5
4 1.2
Father’s occupation 612
Professional 172
28.1 85 29.1 87 29.6
Managerial 126
20.6 61 20.9 65 22.1
Semi-skilled 200
32.7 105
36.0 95 32.3 Unemployed/Pensioner/House duties 114
18.6 41 14.0 47 16.0
Mother’s occupation 637
Professional 175
27.3 80 25.4 95 30.4
Managerial 54 8.5 31 9.8
23 7.3
Semi-skilled 193
30.3 104
33.0 89 28.4 Unemployed/Pensioner/House duties 215
33.8 100
31.7 106
33.9 Father’s education 594 Tertiary
176 29.6
86 28.7
90 30.6
Diploma/Apprenticeship 103
17.3 49 16.3 54 18.4
Year 11/12 167
28.1 87 29.0 80 27.2
Year 10 or less 148
24.9 78 26.0 70 23.8
Mother’s education 633
Tertiary 133
21.0 66 21.0 67 21.1
Diploma/Apprenticeship 102
16.1 55 17.5 47 14.8
Year 11/12 227
35.9 116
36.8 111
34.9 Year 10 or less 171 27.0
78 24.8
93 29.2
Frontiers in Psychology | www.frontiersin.org 4 August 2017 | Volume 8 | Article 1361 fpsyg-08-01361 August 7, 2017 Time: 15:7 # 5
Rozenblat et al. 5-HTTLPR and Disordered Eating distribution was not in Hardy–Weinberg Equilibrium for the subsample providing retrospective reports of sexual and physical stress (l/l = 139, s/l = 255, and s/s = 73; χ 2 = 6.11,
df = 1, p = 0.014). Further descriptive statistics are presented in Table 2. Across all regression models, female sex predicted Drive for Thinness and Bulimia scores, while BMI predicted Drive for Thinness (all p
model discussed below are contained in the Supplementary Materials. Depression There was a significant positive association between depressive symptoms and Drive for Thinness ( β = 0.24, p < 0.001), as well as Bulimia scores ( β = 0.41, p < 0.001); however, there was no evidence of genetic moderation by 5-HTTLPR. There was a significant interaction between depression and sex, with depression associated with greater Drive for Thinness ( β = 0.46, p = 0.001), and to a lesser extent, Bulimia ( β = 0.36, p = 0.018), for females only. There were no other significant effects. Emotional Control Lower emotional control was significantly associated with greater Drive for Thinness ( β = −0.22, p < 0.001) and Bulimia ( β = −0.29, p < 0.001) scores; however, there was no evidence of genetic moderation by 5-HTTLPR. There was a significant interaction between sex and emotional control, with lower emotional control associated with greater Drive for Thinness ( β = −0.45, p = 0.001) and Bulimia (β = −0.67, p < 0.001) for females to a greater extent than for males. However, amongst those with the highest levels of emotional control, females displayed lower levels of Bulimia than did males. Sexual Abuse and Parental Physical Punishment Of the 467 participants (59.1% female) who provided data on sexual abuse and parental physical punishment in the 14th survey, 22 (4.7%) reported sexual abuse, 180 (38.5%) reported mild to moderate parental physical punishment, and 27 (5.8%) reported severed parental physical punishment. See Table 3 for further descriptive statistics. Predictor and outcome variables for this sub-sample did not differ from the overall sample ( t-tests all p > 0.05). TABLE 2 | Descriptive statistics for mean values of continuous predictor and outcome variables in the overall sample (N = 650), in females (N = 326), and in males (N = 324). Mean (SD) Variable Full sample Females Males
Age (years) 15 .72 (0.16) 15 .74 (0.14) 15 .72 (0.17) EDI-2 Bulimia 1 .78 (0.65) 1 .94 (0.73) 1 .62 (0.53) EDI-2 drive for thinness 2 .23 (1.15) 2 .81 (1.22) 1 .64 (0.70) Emotional control 3 .74 (0.63) 3 .62 (0.64) 3 .85 (0.59) Depression 0 .49 (0.34) 0 .59 (0.36) 0 .39 (0.28) BMI 21 .27 (3.28) 21 .20 (3.10) 21 .34 (3.44) There was a direct effect of severe parental physical punishment in predicting Bulimia ( β = 0.14, p = 0.001), but not Drive for Thinness scores. There were no direct effects of sexual abuse or mild-to-moderate parental physical punishment on either disordered eating outcome, although there was an interaction between sexual abuse and sex ( β = 0.28, p = 0.039), with males who reported experiencing sexual abuse tending to display lower Drive for Thinness than those who did not report sexual abuse. This pattern was not evident in females. However, this result did not withstand p-value adjustment for multiple testing.
There was also statistically significant moderation of the relationship between severe parental punishment and bulimia scores by 5-HTTLPR, with greater punishment related to higher Bulimia scores for those with the s-allele only ( β = 0.22, p = 0.0048; see Figure 1). This finding remained after Bonferroni correction for multiple testing was applied. However, this result was based on a sample where genotypic frequencies were not in the Hardy–Weinberg Equilibrium, χ 2
6.11, df = 1, p = 0.014. No other G×E interactions were significant. DISCUSSION This study affirmed the central relationship between depression, emotional control, and physical abuse and adolescent bulimic behaviors and
attitudes regarding thinness. Conversely, 5-HTTLPR did not directly predict any pattern of disordered eating, nor was there conclusive evidence that 5- HTTLPR moderated any risk factor for disordered eating. A statistically significant interaction between 5-HTTLPR and retrospectively reported parental physical punishment was observed; however, genotypes in this subsample were not in Hardy–Weinberg Equilibrium so cautious interpretation and independent replication is needed. Findings from this study support a key role for depression and compromised emotional control in adolescent drive for thinness and bulimic behaviors. The relationships differed by sex in most cases. Female sex predicted greater overall drive for thinness and bulimia, and sex differences were present in the relationships between depression, emotional control, and sexual abuse with disordered eating symptoms. Parental physical punishment was the only variable that showed no sex differences in its relationship TABLE 3 | Descriptive statistics for mean values of continuous predictor and outcome variables in the subsample (N = 467), in females (N = 199), and in males (N = 157). Mean (SD) Variable Full sample Females Males
Age (years) 15 .72 (0.15) 15 .73 (0.15) 15 .71 (0.14) EDI-2 Bulimia 1 .81 (0.67) 1 .92 (0.68) 1 .62 (0.51) EDI-2 drive for thinness 2 .37 (1.20) 2 .79 (1.22) 1 .69 (0.74) Emotional control 3 .74 (0.64) 3 .64 (0.65) 3 .88 (0.59) Depression 0 .51 (0.34) 0 .58 (0.02) 0 .40 (0.28) BMI 21 .19 (3.13) 21 .17 (2.97) 21 .21 (3.37) Frontiers in Psychology | www.frontiersin.org 5 August 2017 | Volume 8 | Article 1361 Yüklə 409,53 Kb. Dostları ilə paylaş:
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