Our study examined whether the early-onset depression phenotype among young adults (probands) is associated with the metabolic syndrome (MetS) and its components, and if MetS characterizes unaffected but high-risk siblings of probands.

We studied three groups of young adults (Mage = 25 years, s.d. = 3.84 years): probands with histories of childhood onset depression – i.e. early-onset phenotype – (n = 293), their unaffected siblings (high-risk siblings, n = 273), and healthy controls (n = 171). Participants completed a full psychiatric interview, physical and laboratory assessments, and self-rating scales. MetS was defined using the criteria of the Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (2001).

Early-onset depression phenotype and being a high-risk sibling were associated with higher MetS composite scores relative to that of controls, but did not differ from one another. With regard to MetS components: Probands and siblings had similarly larger waist circumference and lower HDL than did controls, while siblings and controls had lower triglyceride levels than did probands but did not differ from one another. Groups did not differ on glucose levels and SBP.

Our study extends the literature on the association between MetS and depression and underscores the importance of depression phenotypes: failure to account for the clinical heterogeneity of depression may partly underlie the inconsistent findings regarding its relation to MetS. The results also suggest that, in depression-prone populations, MetS may predate and possibly function as a risk factor for eventual depression.