Common Genetic Variation and Age of Onset of Anorexia Nervosa.

Background: Genetics and biology may influence the age of onset of anorexia nervosa (AN). The aims of this study were to determine whether common genetic variation contributes to age of onset of AN and to investigate the genetic associations between age of onset of AN and age at menarche. Methods: A secondary analysis of the Psychiatric Genomics Consortium genome-wide association study (GWAS) of AN was performed, which included 9335 cases and 31,981 screened controls, all from European ancestries. We conducted GWASs of age of onset, early-onset AN (<13 years), and typical-onset AN, and genetic correlation, genetic risk score, and Mendelian randomization analyses. Results: Two loci were genome-wide significant in the typical-onset AN GWAS. Heritability estimates (single nucleotide polymorphism-h 2) were 0.01-0.04 for age of onset, 0.16-0.25 for early-onset AN, and 0.17-0.25 for typical-onset AN. Early- and typical-onset AN showed distinct genetic correlation patterns with putative risk factors for AN. Specifically, early-onset AN was significantly genetically correlated with younger age at menarche, and typical-onset AN was significantly negatively genetically correlated with anthropometric traits. Genetic risk scores for age of onset and early-onset AN estimated from independent GWASs significantly predicted age of onset. Mendelian randomization analysis suggested a causal link between younger age at menarche and early-onset AN. Conclusions: Our results provide evidence consistent with a common variant genetic basis for age of onset and implicate biological pathways regulating menarche and reproduction.

BDNF levels in adolescent patients with anorexia nervosa increase continuously to supranormal levels 2.5 years after first hospitalization.

BACKGROUND: Brain-derived neurotrophic factor (BDNF) influences brain plasticity and feeding behaviour, and it has been linked to anorexia nervosa in numerous studies. Findings in mostly adult patients point to reduced serum BDNF levels in the acute stage of anorexia nervosa and rising levels with weight recovery. However, it is unclear whether this increase leads to normalization or supranormal levels, a difference that is potentially important for the etiology of anorexia nervosa and relapse. METHODS: We measured serum BDNF at admission (n = 149), discharge (n = 130), 1-year follow-up (n = 116) and 2.5-year follow-up (n = 76) in adolescent female patients with anorexia nervosa hospitalized for the first time, and in healthy controls (n = 79). We analyzed associations with body mass index, eating disorder psychopathology and comorbidities. RESULTS: Serum BDNF was only nominally lower at admission in patients with anorexia nervosa compared to healthy controls, but it increased continuously and reached supranormal levels at 2.5-year follow-up. BDNF was inversely associated with eating disorder psychopathology at discharge and positively associated with previous weight gain at 1-year follow-up. LIMITATIONS: We compensated for attrition and batch effects using statistical measures. CONCLUSION: In this largest longitudinal study to date, we found only nonsignificant reductions in BDNF in the acute stage of anorexia nervosa, possibly because of a shorter illness duration in adolescent patients. Supranormal levels of BDNF at 2.5-year follow-up could represent a pre-existing trait or a consequence of the illness. Because of the anorexigenic effect of BDNF, it might play an important predisposing role for relapse and should be explored further in studies that test causality.

Shared genetic risk between eating disorder- and substance-use-related phenotypes: Evidence from genome-wide association studies.

Eating disorders and substance use disorders frequently co-occur. Twin studies reveal shared genetic variance between liabilities to eating disorders and substance use, with the strongest associations between symptoms of bulimia nervosa and problem alcohol use (genetic correlation [rg ], twin-based = 0.23-0.53). We estimated the genetic correlation between eating disorder and substance use and disorder phenotypes using data from genome-wide association studies (GWAS). Four eating disorder phenotypes (anorexia nervosa [AN], AN with binge eating, AN without binge eating, and a bulimia nervosa factor score), and eight substance-use-related phenotypes (drinks per week, alcohol use disorder [AUD], smoking initiation, current smoking, cigarettes per day, nicotine dependence, cannabis initiation, and cannabis use disorder) from eight studies were included. Significant genetic correlations were adjusted for variants associated with major depressive disorder and schizophrenia. Total study sample sizes per phenotype ranged from ~2400 to ~537 000 individuals. We used linkage disequilibrium score regression to calculate single nucleotide polymorphism-based genetic correlations between eating disorder- and substance-use-related phenotypes. Significant positive genetic associations emerged between AUD and AN (rg = 0.18; false discovery rate q = 0.0006), cannabis initiation and AN (rg = 0.23; q < 0.0001), and cannabis initiation and AN with binge eating (rg = 0.27; q = 0.0016). Conversely, significant negative genetic correlations were observed between three nondiagnostic smoking phenotypes (smoking initiation, current smoking, and cigarettes per day) and AN without binge eating (rgs = -0.19 to -0.23; qs < 0.04). The genetic correlation between AUD and AN was no longer significant after co-varying for major depressive disorder loci. The patterns of association between eating disorder- and substance-use-related phenotypes highlights the potentially complex and substance-specific relationships among these behaviors.

Genome-wide association study identifies eight risk loci and implicates metabo-psychiatric origins for anorexia nervosa.

Characterized primarily by a low body-mass index, anorexia nervosa is a complex and serious illness1, affecting 0.9-4% of women and 0.3% of men2-4, with twin-based heritability estimates of 50-60%5. Mortality rates are higher than those in other psychiatric disorders6, and outcomes are unacceptably poor7. Here we combine data from the Anorexia Nervosa Genetics Initiative (ANGI)8,9 and the Eating Disorders Working Group of the Psychiatric Genomics Consortium (PGC-ED) and conduct a genome-wide association study of 16,992 cases of anorexia nervosa and 55,525 controls, identifying eight significant loci. The genetic architecture of anorexia nervosa mirrors its clinical presentation, showing significant genetic correlations with psychiatric disorders, physical activity, and metabolic (including glycemic), lipid and anthropometric traits, independent of the effects of common variants associated with body-mass index. These results further encourage a reconceptualization of anorexia nervosa as a metabo-psychiatric disorder. Elucidating the metabolic component is a critical direction for future research, and paying attention to both psychiatric and metabolic components may be key to improving outcomes.

Association between neuroendocrinological parameters and learning and memory functions in adolescent anorexia nervosa before and after weight recovery.

A growing body of evidence indicates that hormones play an important role in learning and memory functions as well as in mood modulation. During the acute stage of anorexia nervosa (AN), weight loss has a significant effect on serum levels of estrogen, thyroid hormones, and cortisol. Furthermore deficits in learning and memory functions are evident in patients with eating disorders during emaciation. Hormonal and neuropsychological alterations at least partly remit during weight restoration. We investigated the association between learning and memory functions as well as mood and neuroendocrinological parameters before and after weight gain in adolescent AN. Twenty-eight female subjects with AN, diagnosed according to DSM-IV, were examined before and after weight recovery. Both investigations took place while the patients were receiving hospital treatment, and the results were compared to a control group consisting of 18 age- and IQ-matched normal-weight female adolescents also tested twice within 4 months. Verbal memory and learning were assessed by a German paper-pencil-test (LGT). We performed correlation calculations between neuropsychological functions and depressive symptoms and estrogen, cortisol and free triiodothyronine (fT3) in the plasma at both time points. Compared to normal controls adolescents with AN performed worse in one subtest of the LGT which requires the verbal reproduction of figural material across both time points. Verbal learning was positively correlated with estrogen levels after weight recovery. Depressive symptoms of AN patients significantly decreased during weight rehabilitation and correlated negatively with fT3 at T1. We did not find a relationship between cortisol levels and neuropsychological functions. We observed subtle memory impairments and depressive symptoms in subjects with adolescent AN associated with starvation-induced estrogen and triiodothyronine deficits, respectively. Normalization of body weight and resuming of menses is needed to restore learning and memory functions as well as to alleviate depressive symptoms.