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Seasonal Affective Disorder
Christopher White, MD, JD, MHA
image BASICS
  • Seasonal affective disorder (SAD) is a heterogeneous mood disorder with depressive episodes usually occurring in winter months, with full remissions in the spring and summer.
  • Ranges from a milder form (winter blues) to a seriously disabling illness
  • Must separate out patients with other mood disorders (such as major depressive disorder and bipolar affective disorder) whose symptoms persist during spring and summer months
  • Affects up to 500,000 people every winter
  • Up to 30% of patients visiting a primary care physician (PCP) during winter may report winter depressive symptoms.
  • Predominant age: occurs at any age; peaks in 20s and 30s
  • Predominant sex: female > male (3:1)
  • 1-9% of the general population
  • 10-20% of patients identified as having mood symptoms will have a seasonal component.
The major theories currently involve the interplay of phase-shifted circadian rhythms, genetic vulnerability, and serotonin dysregulation.
  • Melatonin produced by the pineal gland at increased levels in the dark has been linked to depressive symptoms; light therapy on the retina acts to inhibit melatonin secretion.
  • Serotonin dysregulation because it is secreted less during winter months, must be present for light therapy to work, and treatment with SSRIs appears to reverse SAD symptoms
  • Decreased levels of vitamin D, often occurring during low-light winter months, may be associated with depressive episodes in some individuals experiencing SAD symptoms.
  • Some twin studies and a preliminary study on GPR50 melatonin receptor variants have suggested a genetic component.
  • Recent studies indicate an association with the melanopsin gene (OPN4).
  • Increased incidence of depression, ADHD, and alcoholism in close relatives
  • Most common during months of January and February: Patients frequently visit PCP during winter months complaining of recurrent flu, chronic fatigue, and unexplained weight gain.
  • Working in a building without windows or other environment without exposure to sunlight
  • Consider use of light therapy at start of winter (if prior episodes begin in October), increase time outside during daylight, or move to a more southern location.
  • Bupropion (Wellbutrin) is an FDA-approved antidepressant for the prevention of SAD.
Some individuals with SAD have a weakened immune system and may be more vulnerable to infections.
  • Carefully document the presence or absence of prior manic episodes.
  • Screen for the existence of any suicidal ideation and safety risk factors.
  • Remission of symptoms during spring and summer
  • Symptoms have occurred for the past 2 years.
  • Seasonal episodes associated with winter months substantially outnumber any nonseasonal depressive episodes.
  • Under DSM-5, SAD is denoted by adding the “with seasonal pattern” specifier to a diagnosis of major depressive disorder, recurrent.
Use exam to exclude other organic causes for symptoms. Focal neurologic deficits, signs of endocrine dysfunction, or stigmata of substance abuse should prompt further testing.
  • Similar to that of major depression, meaning that organic causes of low energy and fatigue, such as hypothyroidism, anemia, and mononucleosis (or other viral syndromes), need to be considered.
  • Other mood disorders without a seasonal component such as major depression, bipolar disorder, adjustment disorder, or dysthymia
  • Symptoms should not be better accounted for by seasonal psychosocial stressors, which often accompany the winter holiday seasons.
  • Substance abuse
  • Thyroid-stimulating hormone to rule out hypothyroidism
  • CBC to rule out anemia
  • Rule out electrolyte and glucose dysregulation.
  • 25-OH vitamin D level
  • Pregnancy test for women of childbearing potential
  • Urine toxicology screen if substance abuse is a concern
  • Imaging is not useful unless focal neurologic finding or looking to exclude an organic cause.
Lack of evidence to determine whether light therapy or medication should be the first-line agent. Both supported by the literature and in some studies have equal efficacy. Medications have more side effects. Adherence to both remains a critical issue. The ultimate choice depends on the acuity of the patient and the comfort level of the prescribing clinician with each treatment modality (1)[B].
  • SSRIs such as sertraline (Zoloft), paroxetine (Paxil), fluoxetine (Prozac), citalopram (Celexa), and escitalopram (Lexapro) in their traditional antidepressant doses (2)[B]
  • Bupropion (Wellbutrin) is the only antidepressant currently approved by the FDA for the prevention of SAD (3)[B].
  • Patients with a history of ocular disease should be referred for an ophthalmologic exam before phototherapy and for serial monitoring.
  • Patients who fail to respond or who develop manic symptoms or suicidal ideation once treatment is initiated should be considered for psychiatric referral.
  • Phototherapy using special light sources has been shown to be effective in 60-90% of patients, often providing relief with a few sessions (2,4)[B].
  • Variables that can regulate effect are the following:
    • Light intensity: Although the minimum light source intensity is under investigation, at least 2,500 lux is suggested (domestic lights emit, on average, 200 to 500 lux). There is good evidence for 10,000 lux as the recommended source (2)[B].
    • P.953

    • Treatment duration: Exposure time varies based on intensity of light source, with daily sessions of 30 minutes to a few hours.
    • Time of treatment: Most patients respond better by using the light therapy early in the morning.
    • Color of light source: Emerging data suggest that shorter sessions of lower intensity light-emitting diodes enriched in the blue spectrum have equal efficacy to the traditional white light treatment and possibly capable of being delivered in a transcranial manner (5)[B].
  • Light box is placed on table several feet away, and the light is allowed to shine onto the patient's eyes (sunglasses should be avoided). Ensure that the light box has an ultraviolet filter.
  • Most common side effects are eye strain and headache. Insomnia can result if the light box is used too late in the day. Light boxes also can precipitate mania in some patients.
  • Dawn simulation machines gradually increase illumination while the patient sleeps, simulating sunrise while using a significantly less intense light source.
  • Work to reduce stress levels through meditation, progressive relaxation exercises, and/or lifestyle modification.
  • The potential role of vitamin D supplementation is under investigation. Currently, there is a lack of consistent research to satisfactorily demonstrate that treatment improves SAD symptoms. Reported doses vary widely but typically are between 400 and 800 IU/day (6)[B].
Admission Criteria/Initial Stabilization
If the patient develops suicidal ideation as part of his or her depression or mania after treatment is initiated
Regular monitoring by PCP or psychiatrist for response to treatment; patients may become manic when treated with SSRIs or light therapy.
Patient Monitoring
Patients should be seen in the outpatient clinic weekly to biweekly when initiating light or pharmacotherapy to monitor treatment results, side effects, and any increased suicidal thoughts if using SSRIs.
No specific diet modification needed
  • Increase time outdoors during daylight.
  • Rearrange home or work environment to get more direct sunlight through windows.
Symptoms, if untreated, generally remit within 5 months with exposure to spring light, only to return in subsequent winters. If treated, patients usually respond within 3 to 6 weeks.
1. Lam RW, Levitt AJ, Levitan RD, et al. The Can-SAD study: a randomized controlled trial of the effectiveness of light therapy and fluoxetine in patients with winter seasonal affective disorder. Am J Psychiatry. 2006;163(5):805-812.
2. Kurlansik SL, Ibay AD. Seasonal affective disorder. Am Fam Physician. 2012;86(11):1037-1041.
3. Niemegeers P, Dumont GJ, Patteet L, et al. Bupropion for the treatment of seasonal affective disorder. Expert Opin Drug Metab Toxicol. 2013;9(9):1229-1240.
4. Terman M, Terman JS. Light therapy for seasonal and nonseasonal depression: efficacy, protocol, safety, and side effects. CNS Spectr. 2005;10(8): 647-663.
5. Jurvelin H, Takala T, Nissilä J, et al. Transcranial bright light treatment via the ear canals in seasonal affective disorder: a randomized, double-blind dose-response study. BMC Psychiatry. 2014;14:288.
6. Frandsen TB, Pareek M, Hansen JP, et al. Vitamin D supplementation for treatment of seasonal affective symptoms in healthcare professionals: a double-blind randomised placebo-controlled trial. BMC Research Notes. 2014;7:528.
Additional Reading
  • Gordijn MC, ‘t Mannetje D, Meesters Y. The effects of blue-enriched light treatment compared to standard light treatment in seasonal affective disorder. J Affect Disord. 2012;136(1-2):72-80.
  • Howland RH. Vitamin D and depression. J Psychosoc Nurs Ment Health Serv. 2011;49(2):15-18.
  • Mårtensson B, Petterson A, Berglund L, et al. Bright white light therapy in depression: a critical review of the evidence. J Affective Disorders. 2015;182:1-7.
  • Pail G, Huf W, Pjrek E, et al. Bright-light therapy in the treatment of mood disorders. Neuropsychobiology. 2011;64(3):152-162.
  • Thaler K, Delivuk M, Chapman A, et al. Secondgeneration antidepressants for seasonal affective disorder. Cochrane Database Syst Rev. 2011;(12): CD008591.
See Also
  • Bipolar I Disorder; Bipolar II Disorder; Depression
  • Algorithm: Depressive Episode, Major
  • F33.9 Major depressive disorder, recurrent, unspecified
  • F33.0 Major depressive disorder, recurrent, mild
  • F33.1 Major depressive disorder, recurrent, moderate
Clinical Pearls
  • SAD is a subtype of major depressive disorder. Once the patient has a diagnosed mood disorder, such as depression or bipolar, ask whether the symptoms vary in a seasonal pattern to qualify for the diagnosis of SAD. Generally, these patients will report sleeping too much, eating too much (especially carbs and sweets), and gaining weight during winter months.
  • As with all psychiatric diagnoses, ensure that the symptoms are not due to an organic process or better explained by substance abuse.
  • Lack of good evidence to decide whether light therapy or SSRIs should be the first-line agent. Guidelines suggest using SSRIs first if the patient is more acute or has contraindications to light therapy or the clinician is not comfortable with light therapy.
  • Light therapy boxes are available from numerous online suppliers but are not extensively regulated; practitioners should take care to ensure that patients are using devices from reputable suppliers.
  • If using SSRIs, recent studies indicate that some patients may begin to experience increased suicidal thoughts on therapy; these patients need to be monitored closely as outpatients every 1 to 2 weeks. Patients on light therapy also should be monitored closely initially in order to adjust treatment. Once stabilized, both groups of patients can be seen every 4 to 8 weeks during the winter months.
  • All patients who demonstrate suicidal ideation or symptoms of mania should be referred for consideration of hospitalization.