👋👋👋Ever wondered why you sometimes have a lower mood, more fatigue and decreased productivity during the winter months? This actually has several explanations according to neuroscience...our in house consultant steps up and gives the low down on exactly why:

👩‍🔬🧠Amrita: This is due to winter's effect on (1) our circadian rhythms, (2) our serotonin levels, and (3) our vitamin D.

Circadian Rhythms
Peak alertness and sleepiness depends on the circadian rhythm, an internal biological process that regulates the sleep-wake cycle, which is 24 hours in humans. Sunlight exposure is crucial to synchronising the circadian rhythm as it signals to the brain's hypothalamus to release melatonin from the pineal gland and cortisol from the adrenal gland. Melatonin is a hormone that increases in response to diminishing light and promotes
sleep. Cortisol is a hormone that helps promote alertness; it peaks after waking up.
However less sunlight exposure means more
melatonin is released, making us feel tired, impacting daily activities and our cognitive
function by disrupting sleep patterns.

Serotonin
Serotonin is a ‘happy’ hormone; however, it is impacted by decreased exposure to sunlight.
Consequently, studies found that reduced serotonin levels in the winter led to an
increase in depressive-like symptoms in mice (Bazhenova et al. (2019).

Vitamin D
Vitamin D is crucial for mood regulation by protecting neurons and influencing the
production of serotonin. However, there is lower UVB intensity during the winter, which is
required to produce vitamin D. Low vitamin D levels have been linked to symptoms of
depression and seasonal affective disorder (SAD) and an increase in the production of
melatonin (Sarkar, 2017).

So....the changes in our circadian rhythm, our serotonin levels and our vitamin D levels in the winter can lead to
impaired cognitive function and an increase in low mood. Additionally, these factors may lead to the development of seasonal affective disorder (SAD).*

*further research is
required to establish cause and effect on animals compared to humans

Full References:

Bazhenova, E.Y., Fursenko, D.V., Kulikova, E.A., Khotskin, N.V., Sinyakova, N.A. and

Kulikov, A.A. (2019). Effect of Photoperiodic Alterations on depression-like Behavior and

the Brain Serotonin System in Mice Genetically Different in Tryptophan Hydroxylase 2

Activity. Neuroscience Letters, 699, pp.91–96.

doi:https://doi.org/10.1016/j.neulet.2019.01.041.

Sarkar, S. (2017). Vitamin D for Depression with a Seasonal Pattern: an Effective Treatment

Strategy. International Physical Medicine & Rehabilitation Journal, 1(4).

doi:https://doi.org/10.15406/ipmrj.2017.01.00021.

Shawa, N., Rae, D.E. and Roden, L.C. (2018). Impact of Seasons on an Individual’s

chronotype: Current Perspectives. Nature and Science of Sleep, Volume 10, pp.345–354.

doi:https://doi.org/10.2147/nss.s158596.