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Sadness, depression and seasonal affective disorder (SAD)

Katie Stone - Naturopath

Written By:

Katie Stone - Naturopath
Kari Asadorian - Bachelor of Science in Nursing

Medical Reviewer:

Kari Asadorian - Bachelor of Science in Nursing
Jamie Hope - Founder of Methyl-Life

Edited By:

Jamie Hope - Founder of Methyl-Life

Updated On:

February 10, 2025

Table of Contents

    What is the difference between sadness and depression?

    Sadness is a normal emotion that we all feel from time to time. It is described by psychologists as an emotional expression of grief, unhappiness, loss, hopelessness, helplessness, or sorrow.1
    Sadness can also be experienced alongside feelings of loneliness, rejection, disappointment, and dissatisfaction.2

    Sadness is a normal response to distressing and discouraging life events, such as a life change, illness, loss, or relationship difficulties. You may also feel sad after watching an emotional movie or hearing a certain song. In all cases, sadness is usually temporary.
     

    Depression, on the other hand, is a mental illness that impacts your thoughts, behaviour, and daily functioning. Although one of the core features of depression is sadness, not everyone who feels sad meets the criteria for major depressive disorder.3


    Depression is diagnosed according to the criteria outlined in the DSM-5 (Diagnostic and Statistical Manual of Mental Disorders). These criteria include4:

    • Depressed mood and sadness for most of the day for a minimum of two weeks 
    • Loss of interest or pleasure in activities previously enjoyed 
    • At least five other changes in behaviour, including significant weight loss or gain, sleeping too much or too little, restlessness or slowed movements, fatigue or loss of energy, feelings of worthlessness or excessive guilt, diminished concentration, and recurrent thoughts of death or suicide. 
    • These changes must cause significant distress or impairment in your day-to-day life.
       

    Depression may have many causes, including biological, genetic, social, and environmental. It is most commonly attributed to an imbalance of neurotransmitters - particularly serotonin - in the brain. However, recent theories suggest that depression may result from disruptions to certain neurotransmitter systems. Severe stress, life events and reduced levels of GABA may also play a role in the onset of depression.

    What is SAD?

    Seasonal affective disorder (SAD) is a type of recurrent depression that usually occurs between fall and continues into the winter months. It is also referred to as the ‘winter blues’.

    According to the DSM-5, SAD criteria include experiencing depression that begins and ends during a specific season every year (but lifts during other seasons) for at least two years, and typically experiencing more seasons with depression than without over a lifetime.6

    People who live further away from the equator and experience darker winters are more likely to be affected by SAD. It is also more common in people with a history of depression.
     

    SAD is more persistent than sadness and has a significant impact on mood, cognitive function, and physical health.7 Like depression, SAD can result in low mood, reduced energy, and a loss of interest in things you used to enjoy. Other symptoms of SAD may include sleeping more than usual, overeating, and craving carbohydrates. SAD usually goes away by spring or summer. 

    What causes SAD?

    It is thought that SAD may be caused by an imbalance of serotonin, a major neurotransmitter involved with healthy mood. When sunlight diminishes in the fall, some people experience a decrease in SERT, a protein that assists with serotonin transport.8 Reduced Vitamin D - which is activated by sunlight and plays a role in serotonin activity - may also be involved.9


    People with SAD may also be affected by overproduction of melatonin, the hormone that responds to darkness by causing sleepiness.10

    How to tell what you suffer from

    If your low mood seems to persist for no reason, check the criteria for depression as described above. If you identify with at least five of these symptoms, it’s important to seek help from a health professional as soon as possible. 


    If your symptoms seem to appear during the winter months but your mood improves in sunny seasons, you may be affected by SAD. Again, it’s best to talk to a health professional. 


    If you feel sad only occasionally, and your sadness is related to something that has happened, it’s likely that these feelings will pass. The major distinction between sadness and depression is that depression is not linked to a specific cause, and it has a significant impact on your everyday life.

    What can you do to feel better?

    If you are diagnosed with depression or SAD, you may be prescribed medication and/or referred to a psychiatrist.

    Antidepressants

    Antidepressants target certain neurotransmitters in the brain to support mood and behavior.11
    Some of the most common antidepressants are selective serotonin reuptake inhibitors (SSRIs) and serotonin-norepinephrine reuptake inhibitors (SNRIs) which are designed to maintain a steady level of serotonin in your brain. SSRIs work by blocking the reabsorption of serotonin, which makes more serotonin available to send messages between nerve cells.12

    Your health professional can help you to find the right medication and dosage for you.

    Nutrients

    Several nutrients are essential for normal neurotransmitter production, including methylfolate (B9) methylcobalamin (B12) and  S-adenosyl-L-methionine (SAMe). Deficiency in these nutrients is often a factor in depression and SAD.13

    Methylfolate is the active form of folate and plays a key role in the production of serotonin, norepinephrine, and dopamine in the brain.14 It works alongside vitamins B12 and B6 in converting homocysteine to methionine, which is then used to create SAMe, a major methyl donor involved in neurotransmitter synthesis.15

    Up to 70% of people with depression have the MTHFR genetic mutation which compromises their ability to convert dietary folate or synthetic folic acid to l-methylfolate.16 Taking methylfolate as a supplementation has been shown to improve mood, and improve response to antidepressants in people who otherwise do not respond adequately.17

    Vitamin D may also assist with improving mood. Studies suggest that people with low vitamin D levels are at increased risk of both depression and SAD.18 Vitamin D influences the serotonergic system and helps to maintain a normal sleep-wake cycle, both of which are associated with depressive symptoms.19

    Talking therapy

    Also known as psychotherapy, talking therapies include counseling and cognitive-behavioral therapy (CBT). Research suggests that these can be helpful for those with depression or SAD, especially when used alongside antidepressant medication.20

    Finding your purpose

    Research suggests that having a sense of meaning or purpose in life has strong links to improved physical and mental health. Purpose is described as a compass that provides an overall aim in life for directing life goals and guiding decisions. Research suggests that mental well-being is connected to having a sense of purpose. This includes setting and working toward goals, feeling that life makes sense, living according to personal values, and seeing life as meaningful.

    Sadness, depression and seasonal affective disorder (SAD)

    Sadness, depression, and Seasonal Affect Disorder (SAD) may feel similar, but they are distinctly different.

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    Frequently Asked Questions about SAD21

    Can you be depressed without being sad?

    Feeling depressed or losing interest in the activities you used to enjoy are key symptoms of depression. These symptoms must persist for most of the day over at least two weeks, along with fatigue, changes in appetite, difficulty concentrating, thoughts of death, and other criteria as per the DSM-5.

    What is the difference between regular sadness and depression?

    Regular sadness is a normal emotion that affects everyone from time to time. Feelings of sadness usually occur after an event such as loss, disappointment, or a life change. Depression, however, is a mental illness. It may result from disruptions in neurotransmitter systems or genetic traits but has also been linked to severe stress and trauma.

    What does SAD seasonal depression mean?

    Seasonal affective disorder (SAD) is a type of depression that occurs in the darker months of the year. This is because reduced sunlight affects neurotransmitter systems such as serotonin and hormone release, such as melatonin.
    SAD usually begins and ends during fall and winter every year, but improves in spring and summer.22

    What are the six symptoms of SAD?

    Symptoms of SAD usually include:
    1) Trouble falling asleep, sleeping more than usual, or waking up early.
    2) Fatigue, lethargy, and general lack of energy.
    3) Feeling depressed, hopeless, or guilty.
    4) Loss of pleasure in things you once enjoyed.
    5) Difficulty concentrating, poor memory.
    6) Craving carbohydrates, overeating, or gaining weight.

    What helps with seasonal sadness?

    Bright light therapy (BLT) is a first-line treatment for SAD, and numerous studies have shown that it can be effective in reducing symptoms.23 BLT involves sitting in front of a light box (around 18-24 inches away) without looking directly into the light. The light helps to regulate your circadian rhythms, which control the release of hormones such as melatonin.
    Psychotherapy such as cognitive-behavioral therapy (CBT) can help in managing symptoms of SAD by addressing the thoughts and behaviours that contribute to low mood.
    Medications such as selective serotonin reuptake inhibitors (SSRIs) may also be used to treat SAD, either alone or alongside BLT and/or psychotherapy.24
    Improving your intake of methylfolate and B12 is also highly recommended. These nutrients are often most effective when taken in supplement form, as this ensures a concentrated and regular dose.
    Finding your purpose in life - whether with a counsellor or on your own - can also help to lift mood and reduce symptoms of depression.

    References

    1. Hermioni N Lokko, Theodore A Stern; "Sadness: Diagnosis, Evaluation, and Treatment"; The Primary Care Companion For CNS Disorders; 2014 Nov

      https://pmc.ncbi.nlm.nih.gov/articles/PMC4374814/

    2. Sylvia D Kreibig, Frank H Wilhelm, Walton T Roth, James J Gross; "Cardiovascular, electrodermal, and respiratory response patterns to fear- and sadness-inducing films"; Psychophysiology; 2007 Sep

      https://pubmed.ncbi.nlm.nih.gov/17598878/

    3. O'Connor EA, Whitlock EP, Gaynes B, et al.; "Screening for Depression in Adults and Older Adults in Primary Care: An Updated Systematic Review [Internet]."; Agency for Healthcare Research and Quality (US); 2009 Dec

      https://www.ncbi.nlm.nih.gov/books/NBK36406/table/ch1.t1/

    4. O'Connor EA, Whitlock EP, Gaynes B, et al.; "Screening for Depression in Adults and Older Adults in Primary Care: An Updated Systematic Review [Internet]."; Agency for Healthcare Research and Quality (US); 2009 Dec

      https://www.ncbi.nlm.nih.gov/books/NBK36406/table/ch1.t1/

    5. Navneet Bains, Sara Abdijadid; "Major Depressive Disorder"; StatPearls [Internet].; 2023 Apr

      https://www.ncbi.nlm.nih.gov/books/NBK559078/

    6. Sherri Melrose, "Seasonal Affective Disorder: An Overview of Assessment and Treatment Approaches"; Depression Research and Treatment; 2015 Nov

      https://pmc.ncbi.nlm.nih.gov/articles/PMC4673349/

    7. Sadaf Munir, Sasidhar Gunturu, Muhammad Abbas; "Seasonal Affective Disorder"; StatPearls [Internet].; 2024 Apr

      https://www.ncbi.nlm.nih.gov/books/NBK568745/

    8. B. McMahon, S.B. Andersen, M.K. Madsen, L.V. Hjordt, I. Hageman, H. Dam, C. Svarer, S. Da Cunha-Bang, W. Barré, J. Madsen, L. Hasholt, V. Frokjaer, G.M. Knudsen; "P.1.i.037 Patients with seasonal affective disorder show seasonal fluctuations in their cerebral serotonin transporter binding"; European Neuropsychopharmacology Vol. 24, Suppl. 2, Pg. S319; 2014 Oct

      https://www.sciencedirect.com/science/article/abs/pii/S0924977X14705061?via%3Dihub

    9. David C R Kerr, David T Zava, Walter T Piper, Sarina R Saturn, Balz Frei, Adrian F Gombart; "Associations between vitamin D levels and depressive symptoms in healthy young adult women"; Psychiatry Research; 2015 May

      https://pubmed.ncbi.nlm.nih.gov/25791903/

    10. Alfred J Lewy, Bryan J Lefler, Jonathan S Emens, Vance K Bauer; "The circadian basis of winter depression"; Proceedings of the National Academy of Science of the United States of America; 2006 May

      https://pubmed.ncbi.nlm.nih.gov/16648247/

    11. Zachary M. Sheffler, Preeti Patel, Sara Abdijadid; "Antidepressants"; StatPearls [Internet].; 2023 May

      https://www.ncbi.nlm.nih.gov/books/NBK538182/

    12. Andrew Chu, Roopma Wadhwa; "Selective Serotonin Reuptake Inhibitors"; StatPearls [Internet].: 2023 May

      https://www.ncbi.nlm.nih.gov/books/NBK554406/

    13. Gary E Gibson, John P Blass: "Nutrition and Functional Neurochemistry"; Basic Neurochemistry: Molecular, Cellular and Medical Aspects. 6th edition; 1999

      https://www.ncbi.nlm.nih.gov/books/NBK28242

    14. Gerald Martone; "Enhancement of recovery from mental illness with l-methylfolate supplementation"; Perspectives in psychiatric care; 2018 Apr

      https://pubmed.ncbi.nlm.nih.gov/28597528/

    15. H.A. Friedel, K.L. Goa, P. Benfield; "S-Adenosyl-L-Methionine"; Drugs Vol. 38 pg. 389-416; 1989

      https://link.springer.com/article/10.2165/00003495-198938030-00004

    16. Christopher B Kelly, Anne P McDonnell, Timothy G Johnston, Ciaran Mulholland, Stephen J Cooper, Dorothy McMaster, Alun Evans, Alexander S Whitehead; "The MTHFR C677T polymorphism is associated with depressive episodes in patients from Northern Ireland"; Journal of Psychopharmacology (Oxford, England); 2004 Dec

      https://pubmed.ncbi.nlm.nih.gov/15582924/

    17. P.S.A Godfrey, B.K. Toone, T. Bottiglien, M. Laundy, E.H. Reynolds, M.W.P. Carney, et al.; "Enhancement of recovery from psychiatric illness by methylfolate"; The Lancet Vol. 336, Iss. 8712, pg. 392-395; 1990 Aug

      https://linkinghub.elsevier.com/retrieve/pii/0140673690919424

    18. Şerife Akpınar, Makbule Gezmen Karadağ; "Is Vitamin D Important in Anxiety or Depression? What Is the Truth?"; Current nutrition reports; 2022 Sep

      https://pmc.ncbi.nlm.nih.gov/articles/PMC9468237

    19. Vali Musazadeh, Majid Keramati, Faezeh Ghalichi, Zeynab Kavyani, Zohre Ghoreishi, Kamar Allayl Alras, Naryman Albadawi, Abdullah Salem, Mohamed Ismail Albadawi, Raghad Salem, Ahmed Abu-Zaid, Meysam Zarezadeh, Rania A. Mekary; "Vitamin D protects against depression: Evidence from an umbrella meta-analysis on interventional and observational meta-analyses"; Pharmacological Research Vol. 187; 2023 Jan

      https://www.sciencedirect.com/science/article/pii/S1043661822005515

    20. Pim Cuijpersa, Argyris Stringarisb, Miranda Wolpert; "Treatment outcomes for depression: challenges and opportunities"; The Lancet Pschiatry Vol. 7 Iss. 11 pg. 925-927; 2020 Nov

      https://www.thelancet.com/journals/lanpsy/article/PIIS2215-0366(20)30036-5/fulltext

    21. Ian D. Boreham, Nicola S. Schutte; "The relationship between purpose in life and depression and anxiety: A meta-analysis"; Journal of Clinical Psychology Vol. 79, Iss. 12 pg. 2736-2767; 2023 Aug

      https://onlinelibrary.wiley.com/doi/10.1002/jclp.23576

    22. Sherri Melrose; "Seasonal Affective Disorder: An Overview of Assessment and Treatment Approaches"; Depression Research and Treatment; 2015 Nov

      https://pmc.ncbi.nlm.nih.gov/articles/PMC4673349/

    23. Philip D Campbell, Ann M Miller, Mary E Woesner; "Bright Light Therapy: Seasonal Affective Disorder and Beyond"; The Einstein journal of biology and medicine : EJBM; 2019 Sep

      https://pmc.ncbi.nlm.nih.gov/articles/PMC6746555/

    24. Sadaf Munir, Sasidhar Gunturu, Muhammad Abbas; "Seasonal Affective Disorder"; StatPearls [Internet]; 2024 Apr

      https://www.ncbi.nlm.nih.gov/books/NBK568745/

    Katie Stone - Naturopath

    About the Author

    Katie is a qualified Naturopath (BNatMed) and freelance writer from New Zealand. She specializes in all things health and wellness, particularly dietary supplements and nutrition. Katie is also a dedicated runner and has completed more half-marathons than she can count!

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