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Dark truths

Dark truths

Staying in dim light for too long can affect your mental health
A boy in a dim lit room
Representational image | Shutterstock

Like many other IT professionals, 30-year-old Sabita Devi had begun working from home during the COVID-19 pandemic. 

In July 2021, about a year after she started working out of a corner room that rarely sees the sun, she began to experience disruption in her sleep-wake cycle, agitation, and chronic constipation that only responded to laxatives. Moreover, she had lost all her enthusiasm for painting, which had been her stress buster since childhood.  

She had become a friend of the dark after spending all her day in that dimly lit room, completely unaware of the havoc it was causing her mind and body. 

“I felt protected, safe, and comfortable in the dark”, she says. “Whenever my mum drew the curtain open, I would yell at her.” 

It was her irregular periods that made her realise that all was not well with her body. She consulted a doctor who noted her lifestyle and personal history and made a provisional diagnosis of depression along with gynaecological issues. 

The melatonin mess 

The importance of darkness for better sleep and recovery is well-established. Research has shown that melatonin — the hormone produced in the absence of light or at night — governs sleep patterns and mood. Appropriate exposure to light and dark helps in the proper secretion of melatonin, which in turn influences the circadian rhythm or sleep-wake cycle. 

Staying in the dark for long keeps the melatonin secretion high, which ultimately disturbs the sleep-wake pattern. Moreover, lack of light also decreases the production of happy hormones like serotonin and endorphins. Over time, this disproportionate hormone production disrupts the circadian rhythm and begins to damage the brain cells or neurons. All these collectively increase the chances of mental health conditions like depression.  

“Lack of light plays a key role in mental illness,” says Dr Bharath Holla, Department of Psychiatry, National Institute of Mental Health and Neurosciences (NIMHANS), Bengaluru. “Most individuals living in the polar regions and Scandinavian countries suffer from Seasonal Affective Disorders (SAD) in the winters due to scarcity of sunlight.” 

The holistic path 

Humans are diurnal animals (who sleep at night and become active during the day) and their physiological function is based on three elements or doshas — vata, pitta, and kapha. Vata is responsible for every communication and movement in the body, pitta for digestion and metabolism, and kapha for structural integrity and cellular function.  

Dr Kishore Kumar R, Professor of Ayurveda, Department of Integrative Medicine, NIMHANS, says that all three body elements in individuals who do not sleep at night get disturbed, more so vata, which regulates the function of the manas (mind) and is responsible for sleep, sleep-wake cycle, and sensory organ integrity. 

Manas gets influenced by three qualities – sattva (mental composure), rajas (aggressive characteristic) and tamas (low mood and sluggish characteristic). Rajas and tamas fluctuate highly and are responsible for behavioural and mood changes. The rajas characteristic is high during the day (or when exposed to light) and tamas at night (or in the absence of light). 

“In the darkness, the diurnal variation gets disturbed and the first dosha to be affected is vata. Vata is directly linked to rajas and tamas that get disturbed in the brain. As a result, the person develops psychiatric disorders, most often depression,” says Dr Kishore. The severity of the manas dosha depends on the vulnerability. 

According to yoga, surya (sun) is the most important energy provider. It makes the person move and gives enough motivation not only to the mind but the cells of the body to get active and carry on their function. In the deficiency of light, cells go into tamas (darkness). Tamas is responsible for most  illnesses and most importantly is connected to visadha (depression). Sunlight is the best option even if we have artificial light, Dr Kishore further added. 

Neuron death, dumbness, cognition to many more 

A study reveals that rats that are kept in complete darkness for six weeks have anatomical and behavioural features similar to depressed individuals, including dysregulated circadian sleep-wake cycle and an impaired noradrenergic neurotransmitter system , which manages alertness, arousal, and readiness for action. The authors concluded that these rats show apoptosis (programmed cell death) in the aminergic system neuron in the brain – responsible for serotonin, dopamine, and adrenaline production — when compared to animals which are kept in 12:12 light-dark conditions. 

“In humans, the suprachiasmatic nucleus [SCN] located in the hypothalamus of the brain is sensitive to light and acts like a pacemaker to circadian timings, thus regulating the circadian rhythms,” says Dr Surjit Prasad, Associate professor of Psychiatry, Central Institute of Psychiatry, Ranchi. “The neuron tracts projecting to the SCN may lose their function and die in the prolonged absence of light stimuli.” 

Moreover, in a 2018 study published in the journal The Hippocampus Wiley, researchers from Michigan State University studied the effect of dim light and anatomical changes in the brain of Nile grass rats (which like humans sleep at night). When exposed to dim light for four weeks, these rats lost 30 per cent of the capacity of the hippocampus, a critical brain region for learning and memory, and performed poorly on a spatial task they had been trained for. On the contrary, the rats exposed to bright light showed significant improvement in their spatial task. 

“When we exposed the rats to dim light, mimicking the cloudy days of Midwestern winters or typical indoor lighting, the animals showed impairments in spatial learning,” said Dr Antonio “Tony” Nunez, psychology professor and co-investigator on the study in a statement. “This is similar to when people can’t find their way back to their cars in a busy parking lot after spending a few hours in a shopping mall or movie theatre.” 

In the same statement, Dr Joel Soler, another lead author of the study explains that sustained exposure to dim light led to significant reductions in a substance called brain-derived neurotrophic factor – a peptide that helps maintain healthy connections and neurons in the hippocampus, and in dendritic spines, or the connections that allow neurons to “talk” to one another. 

“Dim lights are producing dimwits,” Soler concluded. 

Research has also shown that students who sit in the darker parts of their classroom do worse in tests than those who sit near windows. Another study shows that dark environments made people more likely to lie and behave unethically. 

To conclude, sunlight deprivation can have a devastating effect on mental health. Though there are man-made light sources that mimic the sunlight’s wavelength, the natural source is always a better option and approach. Read more about the effect of sunlight on mental health. 

A woman sipping her morning drink
Representational image | Shutterstock

Devi has now started waking up early and starts her day with the first rays of the sun. When she spoke to Happiest Health, she was sipping her herbal tea, and planning to capture the scenic beauty of the lake and mountains from her windows with her pencils. 

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