Seasonal affective disorder, also known as seasonal depression, causes depressive symptoms during only certain times of the year... and there's a pattern to it?!
Basically, feeling down only 
at certain times of the year is
Gemeint ist damit, dass man sich nur zu
bestimmten Zeiten im Jahr schlecht fühlt.
El hecho de sentirse deprimido 
solamente en ciertas épocas del año
El hecho de sentirse deprimido 
solamente en ciertas épocas del año
On parle de dépression saisonnière
In pratica, sentirsi giù 
in certi periodi dell'anno
Ou seja, a condição de ficar ruim 
em certos momentos do ano