Eduard Vieta
Director of the Institute of Neurosciences at Hospital Clínic, Professor of Psychiatry at the University of Barcelona and researcher at IDIBAPS and CIBERSAM
Having read the article, I think that stating [in the press release] that ‘a new subtype of depression has been identified’ is completely exaggerated and inaccurate. It has been known for decades that some people with depression exhibit symptoms linked to biological rhythms: the DSM itself describes patients with a ‘seasonal pattern’, and a traditional subtype of depression, known as ‘atypical depression’, includes many of the symptoms described in the article, such as daytime hypersomnia. There are also references to ‘seasonal affective disorder’ and its greater response to light therapy in studies from the 1980s and 1990s by Rosenthal, Lewy and other authors.
The study does provide a genetic correlate to the clinical description, suggesting a greater but non-specific genetic component (a higher genetic burden for bipolar disorder and ADHD, amongst other conditions); however, the proportion of variance explained by genetics is very small and heterogeneous to support the claim that this constitutes a subtype of depression.
In summary, the study has its merits, but it in no way supports a new concept or disease; rather, it reinforces some classic clinical observations with further biological data.