Sleep problems, especially nightmares and insomnia, often accompany

depression. This study investigated how nightmares, symptoms of

insomnia, chronotype and sleep duration associate with seasonal

affective disorder, a special form of depression. Additionally, it was

noted how latitude, a proxy for photoperiod, and characteristics of the

place of residence affect the prevalence of seasonal affective disorder

and sleep problems. To study these questions, data from FINRISK 2012

study were used. FINRISK 2012 consists of a random population sample

of Finnish adults aged 25–74 years (n = 4905) collected during winter

from Finnish urban and rural areas spanning the latitudes of 60°N to

66°N. The Seasonal Pattern Assessment Questionnaire was used to

assess symptoms of seasonal affective disorder. Participants with

symptoms of seasonal affective disorder had significantly increased

odds of experiencing frequent nightmares and symptoms of insomnia,

and they were more often evening chronotypes. Associations between

latitude, population size and urbanicity with seasonal affective disorder

symptoms and sleep disturbances were generally not significant,

although participants living in areas bordering urban centres had less

sleep problems than participants from other regions. These data show

that the prevalence of seasonal affective disorder was not affected by

latitude.