Nursing care
Seasonal Affective Disorder nursing care: what to assess and what to do first
Written and reviewed by Dana Whitfield, RN, MSN · 4 min read · Updated September 2026
Short answer
Seasonal affective disorder is a pattern of depressive episodes that recur with the seasons, most often starting in autumn and remitting by spring. It is distinguished from typical depression by hypersomnia and carbohydrate craving rather than insomnia and appetite loss, and first-line treatment is 30 minutes of bright light therapy each morning.
What it is and why it happens
Seasonal affective disorder is a subtype of major depressive disorder or bipolar disorder in which episodes follow a seasonal pattern, typically beginning in autumn or winter and resolving in spring. It is not a separate diagnosis in the DSM-5-TR but a specifier applied when at least two consecutive years show this pattern with full remission at other times of year.
The leading explanation involves reduced sunlight exposure disrupting circadian rhythm and melatonin regulation, along with changes in serotonin availability. Latitude matters: incidence rises further from the equator, where winter daylight hours are shortest. Younger adults and women are affected more often, and a personal or family history of mood disorder raises risk.
How it presents — what you will actually see
The presentation differs from typical major depression in two features that are worth checking specifically: hypersomnia rather than insomnia, and carbohydrate craving with weight gain rather than appetite loss. A patient sleeping ten or more hours a night and still feeling unrested through winter, paired with a strong pull toward bread, pasta and sweets, points toward this pattern rather than classic melancholic depression.
Alongside these atypical features, expect the usual depressive core: low mood, anhedonia, low energy, difficulty concentrating and social withdrawal. Patients often describe a heavy, leaden feeling in the limbs. Because the pattern has repeated for years, many patients normalise it as 'just how I get in winter' rather than reporting it as a mood disorder, so the seasonal history has to be asked for directly.
Nursing assessment priorities
Establish the seasonal pattern explicitly: ask when symptoms start each year, when they resolve, and whether this has repeated for at least two years. A single winter of low mood is not enough to confirm the pattern; screen for prior episodes going back several years.
Screen for suicidal ideation with the same rigour used for any depressive presentation; seasonality does not make the risk lower. Assess sleep quantity and quality, appetite and weight change, and functional impact on work or study during the affected months. Rule out hypothyroidism, which can mimic hypersomnia and low mood, and ask about alcohol use, since some patients self-medicate through winter months.
Interventions and what to do first
Light therapy is first-line and the intervention most specific to this condition: 10,000-lux bright light exposure for approximately 30 minutes each morning, ideally within an hour of waking, sustained through autumn and winter. Response is often seen within one to two weeks, though some patients need longer.
Reinforce that light therapy works best as a consistent daily habit rather than an occasional measure, and that morning timing matters more than evening use for most patients. Cognitive behavioural therapy adapted for seasonal patterns is an effective adjunct or alternative. For patients with moderate to severe symptoms, or when light therapy alone is insufficient, an SSRI such as bupropion or sertraline may be added, started before the expected seasonal onset in patients with a well-established annual pattern.
Complications to watch for
Suicidal ideation can occur even though the disorder is seasonal, and risk should never be assumed low simply because remission is expected by spring. Document any change in ideation at every contact during the symptomatic months.
Weight gain from repeated carbohydrate craving can accumulate over successive winters and contribute to metabolic complications over time. In patients with an underlying bipolar diathesis, light therapy can occasionally trigger a hypomanic or manic switch, so ask about any personal or family history of bipolar disorder before initiating treatment and monitor for irritability, decreased need for sleep or elevated mood once light therapy begins.
Patient teaching before discharge
Teach correct light box use: 10,000 lux, positioned at an angle to the eyes rather than staring directly into it, for about 30 minutes each morning, used consistently from early autumn through winter rather than started only once symptoms are severe. Starting before the usual onset date, if the pattern is well established, can blunt the episode.
Advise on side effects to expect and report: eye strain, headache or mild agitation with light therapy, most of which settle with reduced exposure time. Counsel on maintaining a regular sleep-wake schedule, increasing outdoor light exposure where possible, and continuing any prescribed antidepressant even once mood improves, since stopping early risks relapse before the season has fully turned. Give a clear plan for who to contact if mood worsens or suicidal thoughts emerge.
The next step on this is the same as on everything else here: answer questions and read the rationales. Our mental health practice questions are the closest set to what this page covers.
Common questions
How is seasonal affective disorder different from typical depression?
The core low mood and anhedonia are the same, but seasonal affective disorder typically features hypersomnia and carbohydrate craving with weight gain, rather than the insomnia and appetite loss seen in typical major depression. The pattern also has to recur seasonally for at least two consecutive years.
How long does light therapy take to work?
Many patients notice improvement within one to two weeks of consistent daily use, though some need longer. It needs to be used every morning through the affected season, not just when symptoms flare.
Can light therapy cause harm?
It is generally well tolerated, with eye strain, headache and mild agitation as the most common side effects. In a patient with an underlying bipolar disorder, light therapy can trigger a hypomanic or manic episode, so screening for bipolar history before starting is important.
Does seasonal affective disorder carry a suicide risk?
Yes. Because episodes are expected to remit in spring, the risk can be underestimated, but suicidal ideation should be screened for at every contact during the symptomatic months just as it would be for any depressive episode.
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