Is seasonal affective disorder on the rise with climate change?
By Dr. Manoj Sharma-
[Dr. Manoj Sharma is a Professor in the Department of Social and Behavioral Health and an Adjunct Professor of Internal Medicine at the University of Nevada, Las Vegas, USA. He is a global health promotion expert and president of Health for All, Inc.]
Seasonal affective disorder (SAD) or variation of mood with change in season, especially during months with reduced daylight, is a well-recognized condition that adversely affects the mental health and well-being of many people. It was first described in 1984 and is now classified as a distinct disorder in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision (DSM-5-TR), and related to major depressive disorder and bipolar disorder.
SAD normally exhibits with major depressive spells in the fall or winter months that usually get better by spring or summer months. Recently, the summer variant of SAD has also been reported. The “blues” may be associated with excessive sleeping, overeating, craving for carbohydrates and sugars, and significant tiredness.
It is in the news because of a recent global meta-analysis (a quantitative review of reviews) published in the Journal of Affective Disorders (2025) that found evidence that higher latitude is significantly associated with increased prevalence of SAD. It has been estimated that about 5% of United States adults experience full-blown SAD, with up to 20% feeling a milder version, with greater prevalence in the Northern U.S. According to some reports, growing awareness about this condition and potential rise in summer-pattern SAD driven by increasing heat waves and disrupted sleep patterns due to climate changes, has placed the recent prevalence to 7% with milder forms as high as 40%. The exact understanding of its causation is not clear, but it has been attributed to variations in the circadian rhythm (the human biological clock) and upsetting of neurotransmitters like dopamine, norepinephrine, melatonin, and glutamate. A genomic meta-analysis published in Translational Psychiatry (2018) alluded to the ZBTB20 gene as a potential risk factor for susceptibility to SAD. Evidence also points to the preponderance of this condition in women compared to men. It typically starts in young adulthood (18-30-year-olds). There are screening questionnaires, such as the Seasonal Pattern Assessment Questionnaire (SPAQ) and the Seasonal Health Questionnaire (SHQ), available to diagnose this condition.
How to prevent SAD? There are several ways one can prevent and reduce the adverse effects of SAD. Light is the main tool for regulating the circadian rhythm. So, maximizing exposure to natural sunlight during the day is a potent means. Additionally, in the mornings right after waking, if someone is feeling lows then one can expose themselves to bright light therapy (phototherapy) of a 10,000 lux through a commercially available lamp for 20-30 minutes before starting the day. The optimal distance between the recipient and the light source is recommended to be 60 to 80 cm. In addition, one must set up a consistent sleep schedule by going to bed and waking up at set times. Regular physical activity, particularly walking or another form of aerobic activity during the day, is also helpful. People with SAD tend to withdraw from social activities, and maintaining social connections is also an important aspect of dealing with this condition and preventing it. Healthy eating is also a good strategy to prevent this condition. In healthy eating, avoiding alcohol consumption also plays an important role.
In cases where SAD is aggravated, psychotherapy, especially cognitive behavioral therapy (CBT), antidepressant medication, and Vitamin D supplementation are recommended under the supervision of a healthcare provider.
Dr. Manoj Sharma is a Professor in the Department of Social and Behavioral Health and an Adjunct Professor of Internal Medicine at the University of Nevada, Las Vegas, USA. He is a global health promotion expert and president of Health for All, Inc.