Background. Seasonal affective disorder (SAD) is characterized by recurrent episodes of depression occurring regularly with the onset of winter.

Method. The study was a prospective naturalistic follow-up of the emergence of symptoms of seasonal depression with the passage of time and change in seasons. Participants were screened during summer for SAD. Participants were excluded if they were depressed (BDI >14) during the summer recruitment. Eligible participants prospectively monitored their mood and anxiety by completing the BDI and BAI every 2 weeks from 1 September through to the 31 March.

Results. Forty-five participants met criterion for SAD were included in the final data analyses. Depression scores rose gradually over the 30 week period reaching a peak median score around weeks 22 to 24 (January–February). The ‘hallmark’ physiological symptoms (changes in sleep, appetite and fatigue) emerged earlier in the winter period than cognitive symptoms. The emergence of anxiety symptoms was highly correlated with depressive symptoms, although the median anxiety scores did not reach a clinically significant level. Low self-esteem and poor perceived social support were significantly related to an earlier onset in the emergence of depressive symptoms. Both these factors together resulted in the speediest onset of depression. Poor perceived social support, but not low self-esteem, was associated with earlier emergence of anxiety symptoms.

Conclusions. Physiological symptoms may activate negative cognitions in individuals with risk factors of low self-esteem and poor social support so that the disorder is precipitated earlier and is of longer duration.