Light Pollution: Mental Health Impact And Solutions

Light pollution is the human-made alteration of outdoor light levels from those occurring naturally. It is caused by the overuse and misuse of artificial light, which can shine outward and upward into the sky, rather than focusing it downward. Common sources of light pollution include street lamps, car headlights, and illuminated billboards.

Light pollution has been linked to various adverse effects on human health, including mental health. Research suggests that artificial light at night can negatively impact human health, increasing the risk of obesity, depression, sleep disorders, diabetes, breast cancer, and more.

One of the main ways light pollution affects human health is by disrupting the circadian rhythm, also known as the circadian clock. This 24-hour cycle regulates various physiological processes within the body, such as sleep-wake patterns, brain waves, hormone production, and cell regulation. Disruption of the circadian rhythm has been linked to several medical disorders, including depression, insomnia, cardiovascular disease, and cancer.

Additionally, exposure to artificial light at night can suppress the production of melatonin, a hormone that regulates sleep, immune function, and other biological processes. Lowered levels of melatonin have been associated with increased risks of certain types of cancer, such as breast cancer.

While light pollution can have detrimental effects on mental health, it is important to note that not all light has a negative influence on the human body. Exposure to sunlight, for example, can have positive effects on health, including improving mood and reducing the risk of mood disorders.

Understanding the impact of light pollution on mental health is crucial, as it affects a significant portion of the population. More than 80% of the world population and over 99% of American and European populations reside under light-polluted skies. By recognizing the potential risks associated with light pollution, individuals can take steps to mitigate its effects, such as reducing screen time before bed and investing in blackout curtains or sleep masks.

Circadian rhythm disruption

Circadian rhythm is a 24-hour cycle that influences physiological processes such as brain wave patterns, hormone production, cell regulation, and other biological activities. Circadian rhythm disruption has been linked to several mental health disorders, including depression, insomnia, cardiovascular disease, and cancer.

The human body's master clock, located in the suprachiasmatic nucleus of the hypothalamus, is reset daily to precisely 24 hours by exposure to the light-dark cycle. Light detection and circadian function are closely intertwined, with the retina's photoreceptor cells playing a key role in circadian phototransduction. Intrinsically photosensitive retinal ganglion cells (ipRGCs) are sensitive to blue light and transmit photic information to the master clock.

Exposure to artificial light at night can disrupt the circadian rhythm, leading to negative health consequences. This is because light is the primary cue used by the body to distinguish between day and night. When light exposure is mistimed or constant, biological and behavioural rhythms can become desynchronized.

Several mental health disorders have been associated with circadian rhythm disruption. These include:

Major Depressive Disorder (MDD)

MDD is characterised by alterations in mood, typically increased sadness and/or irritability, accompanied by psychophysiological symptoms such as alterations in sleep, sexual desire, or appetite. There is a positive correlation between the incidence of MDD and modernisation of society, which may be due to increased circadian disruption caused by factors such as light at night, shift work, and jet lag. Human studies have found a link between shift work and MDD, with night shift workers exhibiting increased rates of depression.

Bipolar Disorder (BD)

BD is a genetic disorder characterised by cyclic extreme mood swings between mania and depression. Circadian disruption has been identified as both a state marker and a trait of BD. Environmental circadian disruption, such as jet lag, can induce bipolar episodes in susceptible individuals. Treatment regimens that normalise circadian rhythms have proven effective in treating BD.

Anxiety

While there is some evidence suggesting a link between night shift work, jet lag, and anxiety, recent analyses indicate that mood changes may be primarily due to sleep disturbances rather than direct circadian rhythm disruption. Studies on rodents have revealed relationships between the circadian system and anxiety-like disorders, with disruptions to circadian rhythms leading to increased anxiety-like behaviours.

Schizophrenia (SZ)

SZ is a rare but severely disabling mental disorder characterised by positive symptoms such as delusions and hallucinations, negative symptoms such as flat affect and avolition, and cognitive symptoms such as impaired executive function. Circadian rhythm disruption is a common prodrome of SZ, and there is a strong genetic component to the disorder. Alterations in diurnal rhythms and melatonin and cortisol rhythms have been observed in individuals with SZ.

In summary, circadian rhythm disruption has been implicated in various mental health disorders. While the exact nature of the relationship between circadian disruption and psychopathology is not yet fully understood, both human and rodent studies suggest that it plays a significant role in mood regulation.

Sleep deprivation

Light pollution has been linked to a decrease in the average length of sleep per night for adolescents. A study published in JAMA Psychiatry found that in areas with high outdoor light pollution, the average American teen was likely to get less than the recommended amount of sleep. This is similar to the widely held belief that bright light from indoor screens also has a negative effect on sleep.

Adolescents are at the highest level of risk because they tend to be the most engaged with artificial light from screens. However, these effects can occur in anyone, especially those living in urban and suburban areas with higher outdoor light pollution.

The American Medical Association has stated that:

> [i]t is estimated that white LED lamps have five times greater impact on circadian sleep rhythms than conventional street lamps. Recent large surveys found that brighter residential nighttime lighting is associated with reduced sleep times, dissatisfaction with sleep quality, excessive sleepiness, impaired daytime functioning and obesity.

The human body's 24-hour internal clock, or circadian rhythm, is disrupted by changes in sleep patterns or sleep disorders. This, in turn, impacts both physical and mental health. Science has linked poor sleep with high blood pressure, a weakened immune system, weight gain, a lack of libido, and a higher risk of diabetes, stroke, cardiovascular disease, dementia, and some cancers.

Disruptions to sleep and circadian rhythms are also linked to certain mental disorders, including bipolar disorder, mood swings, paranoia, and anxiety.

Depression

Light pollution has been linked to a range of negative effects on mental health, including an increased risk of depression.

One of the primary mechanisms by which light pollution may contribute to depression is by disrupting the body's circadian rhythm. Circadian rhythm is our internal body clock that regulates sleep-wake cycles, hormone production, and other important physiological processes. Exposure to artificial light at night (LAN) can interfere with this natural cycle, leading to sleep disorders and alterations in hormone production, such as melatonin and serotonin. Studies have found a correlation between LAN and an increased prevalence of depressive symptoms, with a dose-response relationship observed. This means that as the intensity of LAN increases, the risk of developing depressive symptoms also increases.

The impact of LAN on depression may be particularly pronounced in urban areas, where light pollution is more prevalent. The constant illumination from streetlights, billboards, and other artificial light sources can disrupt the natural circadian rhythm, leading to neurochemical and neurostructural changes in the brain. Additionally, the absence of a night sky and the loss of stargazing opportunities may also contribute to mood disturbances. The sense of loss and the limitation of experiences that inspire awe and wonder can further increase the risk of depression.

While the exact mechanisms are not yet fully understood, both physiological and psychological factors are likely to play a role in the relationship between light pollution and depression. More robust epidemiological studies are needed to establish a clearer link and identify potential confounding variables. However, the current evidence suggests that light pollution may be a significant environmental factor contributing to the development of depression.

To mitigate the impact of light pollution on mental health, it is recommended to use warmer bulbs with lower correlated color temperatures (CCT) in indoor and outdoor fixtures. Additionally, setting parameters for electronic device usage at night and creating a dark sleep environment with blackout curtains or sleep masks can help improve sleep quality and potentially reduce the risk of depression.

Anxiety

Light pollution is the excessive or inappropriate use of outdoor artificial light, and it is a growing problem. It is affecting human health, wildlife behaviour and our ability to observe the night sky.

The human body has a natural circadian rhythm, a sleep-wake pattern governed by the natural day/night cycle. Artificial light at night can disrupt this cycle, and this is associated with a range of health problems, including anxiety.

The body's internal clock, or circadian rhythm, is also affected by light pollution. This can lead to a decrease in the production of melatonin, a hormone that promotes sleep and has a range of other health benefits. A disruption in melatonin production can cause sleep deprivation, fatigue, stress, and anxiety.

Blue light, in particular, has been identified as a significant source of these issues. Blue light is a high-energy form of light that is believed to play a major role in regulating the body's circadian rhythms. It is present in sunlight, but the widespread use of artificial blue light from electronic screens and LED lighting has led to increased exposure, especially at night when it is most disruptive.

The effects of light pollution on anxiety are not limited to adolescents. Anyone living in areas with high levels of light pollution, especially in urban and suburban areas, can be impacted.

To reduce the impact of light pollution on anxiety and overall mental health, it is recommended to use warmer lighting in and around the home, set parameters for the use of electronics at night, and create a dark sleep environment with blackout curtains or a sleep mask.

Obesity

Light pollution has been linked to a range of adverse health effects, including obesity. Research suggests that artificial light at night (LAN) may disrupt circadian rhythms and sleep, contributing to the development of obesity. Here is a detailed overview of how light pollution can impact obesity:

Circadian Rhythm Disruption

Light pollution can disrupt the natural circadian rhythm, our internal body clock that regulates various physiological processes. Exposure to LAN can suppress the production of melatonin, a key hormone that regulates sleep and other biological functions. This disruption can lead to altered sleep patterns and changes in eating habits, which may contribute to weight gain and obesity.

Metabolic Alterations

Light pollution has been associated with metabolic alterations that can increase the risk of obesity. Studies have found a link between LAN exposure and metabolic disorders, including alterations in appetite regulation, dysfunctions in metabolic signalling, and changes in hormone production. These metabolic changes can contribute to weight gain and the development of obesity.

Sleep Disturbances

The presence of LAN can interfere with sleep quality and duration. Sleep disturbances, such as insomnia and delayed sleep-phase syndrome, have been linked to obesity. Individuals who experience sleep disruptions may be at a higher risk of developing obesity due to altered hormonal balance and changes in eating patterns.

Behavioural Changes

Light pollution can also impact obesity by influencing behaviour. LAN has been associated with increased night-time snacking and disrupted eating patterns. Additionally, it can affect physical activity levels, as people may be less likely to engage in outdoor activities or exercise in well-lit areas at night. These behavioural changes can contribute to weight gain and obesity.

Melatonin Suppression

Melatonin is a crucial hormone that regulates various physiological processes, including metabolism and immune responses. LAN exposure can suppress melatonin production, leading to potential metabolic disruptions and an increased risk of obesity. Lowered melatonin levels have also been linked to rising rates of obesity in some studies.

In summary, light pollution has been identified as a potential risk factor for obesity. The disruption of circadian rhythms, metabolic alterations, sleep disturbances, behavioural changes, and melatonin suppression are some of the key mechanisms through which light pollution can impact weight gain and obesity. Further research is needed to fully understand the complex relationship between light pollution and obesity and to develop effective strategies to mitigate the negative impacts on human health.

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