Study	Reason for exclusion
Fleer 2014	This study investigated prevention of SAD by psychological therapy and was included in the systematic review on efficacy and safety of psychological therapies (Forneris 2019); however, as it did not investigate the efficacy and safety of agomelatine or melatonin as preventive treatment, it is not relevant for inclusion in this review.
Goodwin 2009	This study investigated prevention of relapse of major depressive disorder, not of SAD.
Leppämäki 2003	This study sought to investigate effects of melatonin on sleep quality, mood and quality of life. Participants were healthy adults with subsyndromal SAD and/or weather‐associated syndrome; however, they had no history of SAD.
Meesters 1999	This study investigated different types of light therapy for prevention of SAD. This study is included in the systematic review on efficacy and safety of light therapy for SAD prevention (Nussbaumer‐Streit 2019); however, as it did not investigate efficacy and safety of agomelatine or melatonin as preventive treatment, it is not relevant for inclusion in this systematic review.
Modell 2005	This study investigated the preventive effects of bupropion XL in people with a history of SAD. This study is included in the systematic review on efficacy and safety of second‐generation antidepressants (Gartlehner 2019); however, as it did not investigate the efficacy and safety of agomelatine or melatonin as preventive treatment, it is not relevant for inclusion in this systematic review.
WELL 100006	This study investigated the preventive effects of bupropion XL in people with a history of SAD. This study is included in the systematic review on efficacy and safety of second‐generation antidepressants (Gartlehner 2019); however, as it did not investigate the efficacy and safety of agomelatine or melatonin as preventive treatment, it is not relevant for inclusion in this systematic review.
WELL AK130936	This study investigated the preventive effects of bupropion XL in people with a history of SAD. This study is included in the systematic review on efficacy and safety of second‐generation antidepressants (Gartlehner 2019); however, as it did not investigate the efficacy and safety of agomelatine or melatonin as preventive treatment, it is not relevant for inclusion in this systematic review.
WELL AKA130930	This study investigated the preventive effects of bupropion XL in people with a history of SAD. This study is included in the systematic review on efficacy and safety of second‐generation antidepressants (Gartlehner 2019); however, as it did not investigate the efficacy and safety of agomelatine or melatonin as preventive treatment, it is not relevant for inclusion in this systematic review.
Wirz‐Justice 1990	This study investigated treatment, not prevention, of SAD. Included participants already had symptoms when the study started.

SAD: seasonal affective disorder