Krystal M. Lewis, PhD is a licensed Clinical Psychologist and Co-Director of Education with the Section on Development and Affective Neuroscience at the National Institute of Mental Health (NIMH) and the Director of the Clinical Psychology Externship Program at the National Institutes of Health. Her group at NIMH (SDAN) studies how information processing in the brain may vary across youth with symptoms of anxiety and depression using neuroimaging and biobehavioral methodology. Dr. Lewis completed her pre-doctoral internship and post-doctoral fellowship training at Ann & Robert H. Lurie Children’s Hospital in Chicago. Dr. Lewis is passionate about the provision of clinical care, training, and mentorship and uses culturally informed, developmentally appropriate, and evidence-based treatment approaches. Her clinical and research interests are focused on identifying mechanisms of change in psychological treatment for pediatric anxiety and mood disorders.
Article2 min read
How Seasonal Affective Disorder (SAD) Affects You All Year Round
- Krystal M Lewis PhD
- Debra Kissen Phd MHSA
- David H Rosmarin PhD
- Sheila Rauch PhD ABPP
- Barbara O Rothbaum PhD ABPP
- Oct 1, 2025
- 2
Not everyone gets excited for the change of seasons. If you experience symptoms of depression or anxiety that appear like clockwork during the same few months every year, you might be experiencing seasonal affective disorder.
What is Seasonal Affective Disorder (SAD)?
Seasonal affective disorder, or SAD, is a type of depression that follows a seasonal pattern. It’s classified into two types: winter-pattern SAD and summer-pattern SAD. Symptoms typically last for four to five months and repeat during the same period each year.
SAD is more than just a case of the winter blues. People with the disorder typically experience symptoms that are severe enough to interfere with daily functioning and quality of life. They may experience negative impact to their work performance, grades, or personal relationships.
Quiz: Which Pattern Does My Seasonal Affective Disorder Follow?
| Winter-pattern SAD | Summer-pattern SAD |
| Hypersomnia (sleeping too much) | Insomnia (sleeping too little) |
| Overeating and weight gain, often with carbohydrate cravings | Undereating and weight loss |
| Social withdrawal | Restlessness, agitation, or episodes of violent behavior |
| Sadness | Anxiety |
Tip sheet:
How to Improve Seasonal Affective Disorder Symptoms
- Bright light therapy: Light therapy boxes may provide highly effective relief to people with winter-pattern SAD. Sitting in front of the lamp for a few minutes each morning can signal your body to produce more of the hormones that boost energy and alertness. If you decide to buy a light therapy box, beware of cheap versions that don’t contain the full spectrum of beneficial light. Go through a trusted retailer or ask your therapist for recommendations.
- Cognitive behavioral therapy (CBT): This type of treatment involves working with a qualified therapist to identify and challenge negative thoughts and promote behavior change while battling seasonal depression.
- Medication: Antidepressants are sometimes used to treat certain types of SAD symptoms. These may be taken year-round or only during symptomatic months. A healthcare provider can help you decide if medication is the right path to take.
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