Seasonal Affective Disorder

A mood disorder characterized by depression that occurs at the same time every year.
Seasonal affective disorder occurs in climates where there is less sunlight at certain times of the year.
Symptoms include fatigue, depression, hopelessness, and social withdrawal.
Treatment includes light therapy (phototherapy), talk therapy, and medications.


Cluster Number:
Wiki Number: PW198
Diagnosis: Seasonal Affective Disorder
US Patients: 1.4% in Florida; 9.9% in Alaska
World Patients: Finland, 9.5%, Ireland, 20%
Sex Ratio:
Age Onset:
Brain Area: retinohypothalamic tract, suprachiasmatic nucleus, retina and pineal gland.
Symptoms: depressed in winter with over-sleeping, over-eating and too little energy, depressed thinking, loss of interest in activities
Causes: lack of available natural light
Medications: SSRI’s, Vitamin D, and othrs
Therapies: light therapy, melatonin, ionized air administration and CBT. Due to skin cancer threat, direct sunlight should be avoided. Eat fish.


The world-wide medical research
reports chosen for each diagnosis 

Clicking each title opens the
PubMed article’s summary-abstract.

  • Bright Light Therapy for Parkinson Disease: A Literature Review and Meta-Analysis of Randomized Controlled Trials
    by Hsu-Tung Huang on November 27, 2021

    Sleep disorders and depression are significant nonmotor symptoms (NMSs) of Parkinson disease (PD). However, few effective, evidence-proven medical treatments are available for alleviating these symptoms. Bright light therapy (BLT) is a well-established treatment for circadian rhythm sleep disorders and seasonal affective disorder. The present study conducted a literature review for the effect of BLT on PD, especially a meta-analysis of randomized controlled trials (RCTs). We searched for studies...

  • Chronobiology of Depression
    by Lucie Bartova on November 19, 2021

    Seasonal fluctuations in mood, drive, energy, sleeping- and eating behavior, weight, as well as further important mental and physical functions, and the utilization of light as an effective treatment option were already described by Hippocrates of Kos and Araeteus, the Cappadocian. The concept of the so-called seasonal affective disorder (SAD) as a disruption of the circadian rhythm precipitated by a deficiency of environmental light during darker seasons was first described in the 1980s....

  • Increase in the left hippocampal dentate gyrus head volume after a 4-week bright light exposure in healthy participants: A randomized controlled study
    by Hirofumi Hirakawa on November 11, 2021

    CONCLUSIONS: This study revealed that 4-week BL significantly increased left DG-head volume in healthy participants. Thus, neurogenesis might be induced by BL in the human DG, which is a completely new mechanism of BLT.

  • Running on Empty: Of Hypopinealism and Human Seasonality
    by Dieter Kunz on November 1, 2021

    The pineal hormone melatonin is the natural transducer of the environmental light-dark signal to the body. Although the responsiveness to photoperiod is well-conserved in humans, only about 25 percent of the human population experiences seasonal changes in behavior. As a consequence, humans seem to have adapted-at least partly-to the seasonal changes in day length. The aim of the study was to demonstrate that the individual melatonin deficit marker DOC (degree of pineal calcification) is related...