Familiality and SNP heritability of age at onset and episodicity in major depressive disorder. Issue 10 (July 2015)

• Record Type: Journal Article
• Authors: Ferentinos, P.; Koukounari, A.; Power, R.; Rivera, M.; Uher, R.; Craddock, N.; Owen, M. J.; Korszun, A.; Jones, L.; Jones, I.; Gill, M.; Rice, J. P.; Ising, M.; Maier, W.; Mors, O.; Rietschel, M.; Preisig, M.; Binder, E. B.; Aitchison, K. J.; Mendlewicz, J.; Souery, D.; Hauser, J.; Henigsberg, N.; Breen, G.; Craig, I. W.; Farmer, A. E.; Müller-Myhsok, B.; McGuffin, P.; Lewis, C. M.
• Is Part Of: Psychological medicine. Volume 45:Issue 10(2015)
• Page Start: 2215
• Page End: 2225
• Publication Date: 2015-07
• Subjects: Psychiatry -- Periodicals; Medicine and psychology -- Periodicals; Clinical psychology -- Periodicals; 616.89
• DOI: 10.1017/S0033291715000215
• Languages: English
• ISSNs: 0033-2917

Abstract

<abstract abstract-type="normal"> <title> <x content-type="archive" xml:space="preserve">Abstract</x> </title> <sec id="sec_a1"> <title>Background</title> <p>Strategies to dissect phenotypic and genetic heterogeneity of major depressive disorder (MDD) have mainly relied on subphenotypes, such as age at onset (AAO) and recurrence/episodicity. Yet, evidence on whether these subphenotypes are familial or heritable is scarce. The aims of this study are to investigate the familiality of AAO and episode frequency in MDD and to assess the proportion of their variance explained by common single nucleotide polymorphisms (SNP heritability).</p> </sec> <sec id="sec_a2" sec-type="methods"> <title>Method</title> <p>For investigating familiality, we used 691 families with 2–5 full siblings with recurrent MDD from the DeNt study. We fitted (square root) AAO and episode count in a linear and a negative binomial mixed model, respectively, with family as random effect and adjusting for sex, age and center. The strength of familiality was assessed with intraclass correlation coefficients (ICC). For estimating SNP heritabilities, we used 3468 unrelated MDD cases from the RADIANT and GSK Munich studies. After similarly adjusting for covariates, derived residuals were used with the GREML method in GCTA (genome-wide complex trait analysis) software.</p> </sec> <sec id="sec_a3" sec-type="results"> <title>Results</title> <p>Significant familial clustering was found for both AAO (ICC = 0.28) and episodicity (ICC = 0.07). We calculated from respective ICC estimates the maximal additive heritability of AAO (0.56) and episodicity (0.15). SNP heritability of AAO was 0.17 (<italic>p</italic> = 0.04); analysis was underpowered for calculating SNP heritability of episodicity.</p> </sec> <sec id="sec_a4" sec-type="conclusion"> <title>Conclusions</title> <p>AAO and episodicity aggregate in families to a moderate and small degree, respectively. AAO is under stronger additive genetic control than episodicity. Larger samples are needed to calculate the SNP heritability of episodicity. The described statistical framework could be useful in future analyses.</p> </sec> </abstract>